The 2016 Nobel Prize in physics has been awarded to David Thouless, Duncan Haldane and Michael Kosterlitz, three theoretical physicists whose research used the unexpected mathematical lens of topology to investigate phases of matter and the transitions between them.
Topology is a branch of mathematics that deals with understanding shapes of objects; it’s interested in “invariants” that don’t change when a shape is deformed, like the number of holes an object has. Physics is the study of matter and its properties. The Nobel Prize winners were the first to make the connection between these two worlds.
Everyone is used to the idea that a material can take various familiar forms such as a solid, liquid or gas. But the Nobel Prize recognizes other surprising phases of matter – called topological phases – that the winners proposed theoretically and experimentalists have since explored.
Topology is opening up new platforms for observing and understanding these new states of matter in many branches of physics. I work with theoretical aspects of cold atomic gases, a field which has only developed in the years since Thouless, Haldane and Kosterlitz did their groundbreaking theoretical work. Using lasers and atoms to emulate complex materials, cold atom researchers have begun to realize some of the laureates’ predictions – with the promise of much more to come.
Cold atoms get us to quantum states of matter
All matter is made up of building blocks, such as atoms. When many atoms come together in a material, they start to interact. As the temperature changes, the state of matter starts to change. For instance, water is a liquid until a fixed temperature, when it turns into vapor (373 degrees Kelvin; 212 degrees Fahrenheit; 100 degrees Celsius); and if you cool, solid ice forms at a fixed temperature (273K; 32℉; 0℃). The laws of physics give us a theoretical limit to how low the temperature can get. This lowest possible temperature is called absolute zero (0K) (and equals -460℉ or -273℃).
Classical physics governs our everyday world. Classical physics tells us that if we cool atoms to really low temperatures, they stop their normally constant vibrating and come to a standstill.
But really, as we cool atoms down to temperatures approaching close to 0K, we leave the regime of classical physics – quantum mechanics begins to govern what we see.
In the quantum mechanical world, if an object’s position becomes sharply defined then its momentum becomes highly uncertain, and vice versa. Thus, if we cool atoms down, the momentum of each atom decreases, and the quantum uncertainty of its position grows. Instead of being able to pinpoint where each atom is, we can now only see a blurry space somewhere within which the atom must be. At some point, the neighboring uncertain positions of nearby atoms start overlapping and the atoms lose their individual identities. Surprisingly, the distinct atoms become a single entity, and behave as one coherent unit – a discovery that won a previous Nobel.
This new, amazing way atoms organize themselves at very low temperatures results in new properties of matter; it’s no longer a classical solid in which the atoms occupy periodic well-defined positions, like eggs in a carton.
Instead, the material is now in a new quantum state of matter in which each atom has become a wave with its position no longer identifiable. And yet the atoms are not moving around chaotically. Instead, they are highly coherent, with a new kind of quantum order. Just like laser beams, the coherent matter waves of superfluids, superconductors and magnets can produce interference patterns.
Physicists have known about quantum order in superfluids and magnets in three dimensions since the middle of the last century. We understand that the order is lost at a critical temperature due to thermal fluctuations. But in two dimensions the situation is different. Early theoretical work showed that thermal fluctuations would destroy the quantum order even at very low temperatures.
What Thouless, Haldane and Kosterlitz addressed were two important questions: What is the nature of the quantum ordered state of superfluids, superconductors and magnets in low dimensions? What is the nature of the phase transition from the ordered to the disordered state in two dimensions?
Thinking about defects
Kosterlitz and Thouless’s innovation was to show that topological defects – vortex and anti-vortex whirls and swirls – are crucial to understand the magnetic and superfluid states of matter in two dimensions. These defects are not just local perturbations in the quantum order; they produce a winding or circulation as one goes around it. The vorticity, which measures how many times one winds around, is measured in integer units of the circulation.
Kosterlitz and Thouless showed that at low temperatures, a vortex is bound up with an anti-vortex so the order survives. As the temperature increases, these defects unbind and grow in number and that drives a transition from an ordered to a disordered state.
It’s been possible to visualize the vortices in cold atomic gases that Kosterlitz and Thouless originally proposed, bringing to life the topological defects they theoretically proposed. In my own research, we’ve been able to extend these ideas to quantum phase transitions driven by increasing interactions between the atoms rather than by temperature fluctuations.
Figuring out step-wise changes in materials
The second part of the Nobel Prize went to Thouless and Haldane for discovering new topological states of matter and for showing how to describe them in terms of topological invariants.
Physicists knew about the existence of a phenomenon called the quantum Hall effect, first observed in two dimensional electrons in semiconductors. The Hall conductance, which is the ratio of the transverse voltage and the current, was observed to change in very precise integer steps as the magnetic field was increased. This was puzzling because real materials are disordered and messy. How could something so precise be seen in experiments?
It turns out that the current flows only in narrow channels at the edges and not within the bulk of the material. The number of channels is controlled by the magnetic field. Every time an additional channel or lane gets added to the highway, the conductance increase by a very precise integer step, with a precision of one part in billion.
Thouless’ insight was to show that the flow of electrons at the boundaries has a topological character: the flow is not perturbed by defects – the current just bends around them and continues with its onward flow. This is similar to strong water flow in a river that bends around boulders.
Thouless figured out that here was a new kind of order, represented by a topological index that counts the number of edge states at the boundary. That’s just like how the number of holes (zero in a sphere, one in a doughnut, two in glasses, three in a pretzel) define the topology of a shape and the robustness of the shape so long as it is deformed smoothly and the number of holes remains unchanged.
Global, not local, properties
Interacting topological states are even more remarkable and truly bizarre in that they harbor fractionalized excitations. We’re used to thinking of an electron, for instance, with its charge of e as being indivisible. But, in the presence of strong interactions, as in the fractional quantum Hall experiments, the electron indeed fractionalizes into three pieces each carrying a third of a charge!
Haldane discovered a whole new paradigm: in a chain of spins with one unit of magnetic moment, the edge spins are fractionalized into units of one-half. Remarkably, the global topological properties of the chain completely determine the unusual behavior at the edges. Haldane’s remarkable predictions have been verified by experiments on solid state materials containing one-dimensional chains of magnetic ions.
Topological states are new additions to the list of phases of matter, such as, solid, liquid, gas, and even superfluids, superconductors and magnets. The laureates’ ideas have opened the floodgates for prizeworthy predictions and observations of topological insulators and topological superconductors. The cold atomic gases present opportunities beyond what can be achieved in materials because of the greater variety of atomic spin states and highly tunable interactions. Beyond the rewards of untangling fascinating aspects of our physical world, this research opens the possibility of using topologically protected states for quantum computing.
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This artist’s representation shows an electron beam (in purple) being used to create a 2D superlattice made up of quantum dots having extraordinary atomic-scale precision and placement.
Credit: Peter Allen
Control is a constant challenge for materials scientists, who are always seeking the perfect material — and the perfect way of treating it — to induce exactly the right electronic or optical activity required for a given application.
As electronics and the devices that incorporate them — smartphones, laptops and the like — have become smaller and smaller, the semiconductor transistors that power them have shrunk to the point of being not much larger than an atom. They can’t get much smaller. To overcome this limitation, researchers are seeking ways to harness the unique characteristics of nanoscale atomic cluster arrays — known as quantum dot superlattices — for building next generation electronics such as large-scale quantum information systems. In the quantum realm, precision is even more important.
New research conducted by UC Santa Barbara’s Department of Electrical and Computer Engineering reveals a major advance in precision superlattices materials. The findings by Professor Kaustav Banerjee, his Ph.D. students Xuejun Xie, Jiahao Kang and Wei Cao, postdoctoral fellow Jae Hwan Chu and collaborators at Rice University appear in the journal Nature Scientific Reports.
Their team’s research uses a focused electron beam to fabricate a large-scale quantum dot superlattice on which each quantum dot has a specific pre-determined size positioned at a precise location on an atomically thin sheet of two-dimensional (2-D) semiconductor molybdenum disulphide (MoS2). When the focused electron beam interacts with the MoS2 monolayer, it turns that area — which is on the order of a nanometer in diameter — from semiconducting to metallic. The quantum dots can be placed less than four nanometers apart, so that they become an artificial crystal — essentially a new 2-D material where the band gap can be specified to order, from 1.8 to 1.4 electron volts (eV).
This is the first time that scientists have created a large-area 2-D superlattice — nanoscale atomic clusters in an ordered grid — on an atomically thin material on which both the size and location of quantum dots are precisely controlled. The process not only creates several quantum dots, but can also be applied directly to large-scale fabrication of 2-D quantum dot superlattices. “We can, therefore, change the overall properties of the 2-D crystal,” Banerjee said.
Each quantum dot acts as a quantum well, where electron-hole activity occurs, and all of the dots in the grid are close enough to each other to ensure interactions. The researchers can vary the spacing and size of the dots to vary the band gap, which determines the wavelength of light it emits.
“Using this technique, we can engineer the band gap to match the application,” Banerjee said. Quantum dot superlattices have been widely investigated for creating materials with tunable band gaps but all were made using “bottom-up” methods in which atoms naturally and spontaneously combine to form a macro-object. But those methods make it inherently difficult to design the lattice structure as desired and, thus, to achieve optimal performance.
As an example, depending on conditions, combining carbon atoms yields only two results in the bulk (or 3-D) form: graphite or diamond. These cannot be ‘tuned’ and so cannot make anything in between. But when atoms can be precisely positioned, the material can be designed with desired characteristics.
“Our approach overcomes the problems of randomness and proximity, enabling control of the band gap and all the other characteristics you might want the material to have — with a high level of precision,” Xie said. “This is a new way to make materials, and it will have many uses, particularly in quantum computing and communication applications. The dots on the superlattice are so close to each other that the electrons are coupled, an important requirement for quantum computing.”
The quantum dot is theoretically an artificial “atom.” The developed technique makes such design and “tuning” possible by enabling top-down control of the size and the position of the artificial atoms at large scale.
To demonstrate the level of control achieved, the authors produced an image of “UCSB” spelled out in a grid of quantum dots. By using different doses from the electron beam, they were able to cause different areas of the university’s initials to light up at different wavelengths.
“When you change the dose of the electron beam, you can change the size of the quantum dot in the local region, and once you do that, you can control the band gap of the 2-D material,” Banerjee explained. “If you say you want a band gap of 1.6 eV, I can give it to you. If you want 1.5 eV, I can do that, too, starting with the same material.”
This demonstration of tunable direct band gap could usher a new generation of light-emitting devices for photonics applications.
Story Source: Materials provided byUniversity of Chicago Original written by Whitney Clavin.Note: Content may be edited for style and length.
Xuejun Xie, Jiahao Kang, Wei Cao, Jae Hwan Chu, Yongji Gong, Pulickel M. Ajayan, Kaustav Banerjee. Designing artificial 2D crystals with site and size controlled quantum dots. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-08776-3


Researchers made colors disappear, turned common red bricks into batteries, and granted the senses of sight and touch to a nonhuman system. Was it magic? Nope: science! Read on for this week’s coolest discoveries.
What is it? “Intrinsic color” — the kind we usually perceive — is created by different wavelengths of light being absorbed by the atoms, molecules, and surface structures that make up whatever we’re looking at. But now engineers at the University of Pennsylvania have designed a “system of nanoscale semiconductor strips” that makes the intrinsic color of a material disappear.
Why does it matter? According to a Penn Engineering news release, the new system — described in an article in Nature Communications — could have uses in “holographic displays and optical sensors,” and could “pave the way for new types of microlasers and detectors, fundamental elements of long-sought-after photonic computers.”
How does it work? The strips take advantage of so-called structural color. One example of structural color is peacock feathers, which have no one intrinsic color. The birds’ brilliant plumage is the effect of different wavelengths reflecting off the nanoscale structures on their feathers’ surfaces, colliding and interfering to create that iridescent sheen. The Penn researchers designed their nanoscale strips from tungsten disulfide on a gold backing. At only a few dozen atoms thick, the strips “are spaced out at suboptical wavelength sizes, allowing them to give off the type of structural color” exemplified by peacock feathers. In this way the strips, which should look blue, appear to have no color at all. If biological materials like feathers can have little to no intrinsic color but appear colorful due to their nanoscale structures, lead researcher Deep Jariwala said, this study suggests the reverse is also true: “If a material does have a strong intrinsic color, we show that one can do the opposite and make it disappear with appropriate nanostructuring.”
What is it? Engineers at Washington University in St. Louis devised a way to turn the common red brick — same kind as you can pick up at the hardware store — into an energy storage unit.
Why does it matter? Buildings whose walls have the ability to charge a phone or a computer or supply electricity to a light fixture have an obvious appeal, and the researchers imagine their creation could be useful in, for instance, emergency lighting situations, perhaps when connected with solar cells. And as they point out in their article in Nature Communications, fired red brick is “a universal building material” whose use dates back 5,000 years. That’s a lot of potential batteries.
How does it work? The Washington University team developed the energy storage device by creating “a coating of the conducting polymer PEDOT, which is comprised of nanofibers that penetrate the inner porous network of a brick; a polymer coating remains trapped in a brick and serves as an ion sponge that stores and conducts electricity,” explains chemistry professor Julio D’Arcy.
What is it? Scientists at the University of Chicago’s Pritzker School of Molecular Engineering discovered a “simple modification” that enables quantum systems to operate 10,000 times longer than before.
Why does it matter? Business and governments have eyed quantum computing as a way to create “virtually unhackable networks or extremely powerful computers,” even a quantum internet. But they have been held back by the fragility of quantum systems, which require extreme stability. Such systems now operate on the order of milliseconds. The U. of C. discovery points the way forward, said David Awschalom, lead author of a new study in Science: “This breakthrough lays the groundwork for exciting new avenues of research in quantum science. It enables new research opportunities previously thought impractical.”
How does it work? By, essentially, “tricking” the quantum system into thinking there’s no background noise, using electromagnetic pulses in addition to a precisely tuned continuous alternating magnetic field. Postdoctoral researcher Kevin Miao said, “To get a sense of the principle, it's like sitting on a merry-go-round with people yelling all around you. When the ride is still, you can hear them perfectly, but if you're rapidly spinning, the noise blurs into a background.”
What is it? Scientists at Singapore’s Nanyang Technological University combined “skin-like electronics with computer vision” into an artificial intelligence system that can recognize hand gestures.
Why does it matter? The technology could have uses in surgical robots, gaming interfaces, and robot-aided workplaces. Markus Antonietti, the director of Germany’s Max Planck Institute of Colloids and Interfaces — who was not involved in the project — said in NTU’s press release that “the findings from this paper bring us another step forward to a smarter and more machine-supported world. Much like the invention of the smartphone, which has revolutionized society, this work gives us hope that we could one day physically control all of our surrounding world with great reliability and precision through a gesture.” The paper was published in Nature Electronics.
How does it work? The Singaporean team’s “bio-inspired” system includes a stretchable sensor, made of single-walled carbon nanotubes, that fits over the hand, while the AI system combines three different neural network approaches: one concerning visual processing, one concerning somatosensory processing and one that fuses the two. NTU’s Chen Xiaodong, the study’s lead author, said the technology is “unique” in that it resembles “the somatosensory-visual fusion hierarchy in the brain.”
What is it? Researchers at Texas A&M University are working on a new method that uses machine learning to improve the quality of low-resolution images produced by electron microscopes.
Why does it matter? The technique may have solved an old problem in electron microscopy, which — as the name suggests — obtains images by means of a high-energy electron beam aimed at the sample. Higher resolution can be achieved by cranking up the energy, only this can damage the sample under examination, similar to how ultraviolet rays can damage the skin. “There's always that dilemma for scientists,” said engineering professor Yu Ding, who co-authored an article on the technique in IEEE Transactions on Image Processing. “To maintain the specimen's integrity, high-energy electron beams are used sparingly. But if one does not use energetic beams, high-resolution or the ability to see at finer scales becomes limited.”
How does it work? Ding and colleagues trained a neural network on pairs of images at low and high resolutions, which enabled the AI to learn how to enhance details on other low-res images. Ding explained, “Normally, a high-energy electron beam is passed through the sample at locations where greater image resolution is desired. But with our image processing techniques, we can super-resolve an entire image by using just a few smaller-sized, high-resolution images. This method is less destructive since most parts of the specimen sample needn't be scanned with high-energy electron beams."


Photons can have half-integer values of angular momentum when they are confined to fewer than three dimensions. That is the conclusion of physicists in Ireland, who have revived an experiment first done in the 1830s to show that photons are not limited to having just integer values of angular momentum. The discovery could have applications in quantum computing and could also boost the capacity of optical-fibre data transmission.
The angular momentum of light comes in two varieties: spin and orbital. Spin is associated with optical polarization, which is the orientation of light’s electric-field oscillations. Orbital angular momentum rotates a light beam’s wavefront around its propagation axis, giving it a corkscrew shape.
Individually, the two types of angular momentum come in multiples of the reduced Planck’s constant, ħ. For spin, those multiples are either +1 or –1, while the orbital variety can take any integer value. To date, physicists have assumed that a photon’s total angular momentum is simply the sum of these two parts and that it therefore comes in integer multiples of ħ. But in the latest research, Paul Eastham of Trinity College Dublin and colleagues have shown that the total angular momentum can in fact take on half-integer values.
Inspiration for the work, says Eastham, came from celebrations of the 200th anniversary of the birth of Irish mathematician William Hamilton in 2005. Hamilton and physicist Humphrey Lloyd showed, in the 1830s, that a beam of light passing through a “biaxial” crystal takes on the shape of a hollow cylinder. The void at its centre is now known to be caused by the light acquiring orbital angular momentum. The bicentennial prompted renewed interest in this effect among physicists in Ireland, says Eastham, who joined Trinity College in 2009 and then started to think about exactly how such beams behave quantum-mechanically.
Eastham drew on work from the early 1980s regarding matter particles confined to two dimensions, in particular Frank Wilczek’s prediction that electrons travelling on a plane around a magnetic flux could have non-integer angular momentum. Eastham and colleagues Kyle Ballantine and John Donegan realized that a similar effect could occur within a beam of light having spin and orbital momentum. Given that Maxwell’s equations require rotational symmetry in three dimensions for the normal summing of a photon’s angular momentum, and noting that the symmetry of a beam in a biaxial crystal is limited to rotation about its axis of propagation, they worked out that the beam’s photons should have half-integer angular momentum.
“The vortex of a beam with orbital angular momentum is a topological defect; it is a knot that you can’t untie,” he says. “We realized it is possible to make beams with a more complicated topological defect, where both phase and polarization vary across the beam.”
To demonstrate light’s fractional angular momentum experimentally, the team shone a laser beam through a biaxial crystal preceded by a polarizer and then split the beam inside an interferometer. Employing a technique devised by Miles Padgett at the University of Glasgow in the UK, they rotated the beam in one arm of the interferometer before recombining it with the (un-rotated) beam travelling through the other arm, and then measured the output.
To analyse the beam’s total angular momentum, the researchers rotated the orbital and spin components by different amounts: 180° and 90°, respectively. This enabled them to sort photons into two groups with half-integer values: those having +ħ/2 and others having –ħ/2. To make sure individual photons had angular momentum of ħ/2 – rather than half of them carrying ħ and the other half zero – they measured the beam’s “shot noise”. This noise will be lower if the quantum of angular momentum flow is smaller, which is what they observed.
“In my undergraduate physics lectures I learnt that light has integer angular momentum, but we have now shown that it doesn’t have to,” says Eastham, who adds that he hopes the research will encourage others to “look more at the implications of low dimensions in optics”. He also points, somewhat tentatively, to possible applications of the work, including an optical analogue of “topological” quantum computing and a new way of exploiting angular momentum to increase bandwidth in optical-fibre communications.
Michael Berry of the University of Bristol describes the demonstration as “a new wrinkle on the old subject of the angular momentum of light, supported by a clever experiment”. Padgett says that the Trinity group has provided a “lovely treatment of light transmission through biaxial crystals, particularly as regards the angular momentum content of the light”. However, he adds that it is not clear whether the new findings could be applied to fibre-based communications.
The research is published in Science Advances.


Making teleportation more energy-efficient
An international team of researchers has achieved an important theoretical result by finding that quantum teleportation – the process of transporting quantum information at the speed of light, which could in theory be used to teleport macroscopic objects and, one day, even humans – can be achieved in a much more energy-efficient way than was previously thought.
How teleportation works
For the best part of the twentieth century, teleportation was dismissed as purely as a science fiction pipe dream. The problem lay in the approach: the only possible way to achieve it, scientists thought, would be to measure the position and momentum of every single atom of the object to be teleported, send it to its destination using classical (non-quantum) information, and finally rebuild it based on the set of "instructions" received. But science says that the first step – the perfect measurement of a particle – is simply impossible due to Heisenberg's uncertainty principle.In 1993, however, researchers showed that teleportation was indeed possible in principle, as long as the original object is destroyed in the process. The mechanism circumvents Heisenberg's uncertainty principle by exploiting one of the many quirks of quantum mechanics – a phenomenon called "quantum entanglement".
Entanglement happens when a pair of particles, such as electrons and protons, are intrinsically bound together. Once entanglement is achieved, the two particles will maintain synchronization, whether they are next to each other or on opposite sides of the Universe. As long as the entangled state is maintained, if one particle changes its state, the other will instantaneously do so as well.
As you might expect, the theory is quite hard to get one's head around, but let's give it a shot.
Imagine that we have an object "A" that we want to teleport. We also have "B" and "C", which are entangled with each other, but not with A. Now let's transport object B to the sending station right next to A, and object C to the receiving station.
Back in 1993, scientists found that they could scan A and B together, extracting partial information from A. Scanning scrambles the quantum states of both A and B, and because B and C are entangled, all the remaining information from A is instantly transmitted to C. Using lasers, fiber optics or any other traditional means of communication, the sending station can then send the partial information it had gathered about A to the receiving station. Now all the information about A is at the receiving station, and object C can be reassembled as a perfect copy of the original. Object A is destroyed in the process – hence we have teleportation, and not replication.
One of the prerequisites for teleportation is that B and C must first have interacted closely to create an entangled state, and then must be able to be transported to their final destinations. This means that we can teleport objects to places we've been before but not, say, to a galaxy or planet that we've never visited.
As already mentioned, the system works because B and C are entangled. But there's a problem: over time, as objects are teleported, the entangled state is slowly depleted. It can be renewed by having B and C interact closely again, but this means transporting manually (without teleportation) both objects to the same place, and then back again to the sending and receiving stations. The idea is that one difficult journey can allow for many quick transfers in the future.
Five years ago, physicists came up with an alternative approach to teleportation that is faster because it doesn't require the correction of C, but which is highly impractical because the entangled state is destroyed every single time that information is teleported.
In both cases, entanglement can be effectively thought of as the "fuel" that powers teleportation.
Now, a group of physicists at Cambridge, University College London and the University of Gdansk have worked out how entanglement could be "recycled" to increase the efficiency of these connections. They have developed two protocols that generalize the two known methods of quantum teleportation and provide an optimal solution in which the entangled state holds much longer for the teleportation of multiple objects, while eliminating the need for error correction.The first of these protocols can be used to teleport quantum states sequentially, while the second makes it possible to teleport several states at the same time, which speeds up the process and is of particular interest for applications in quantum computing.
The result obtained by the researchers is purely theoretical and didn't involve any quantum information actually being teleported from one place to another. But interest in quantum teleportation is quickly surging, and labs around the world are racing to demonstrate the ability to teleport information at longer and longer distances – last year, for instance, scientists reported teleporting photons over a record 143 km (89 miles) – so it might not be long until this theoretical result is actually put into practice.
But wait – didn't we say that distance shouldn't matter at all when two particles are entangled? While it is true that two particles remain entangled regardless of their distance, for the time being, we are only able to store the entangled state for a very short period of time. This means that, in practice, scientists must create an entangled state between particles B and C and then rush them to the sending and receiving stations as quickly as possible, before the entangled state is depleted. During the transmission, photon losses and signal decoherence also increase with distance, which makes things considerably worse – although scientists are actively tackling the problem.
Beam me up, Scotty
So will the teleportation of people ever be feasible? Last November, a group of Chinese scientists have managed to achieve teleportation from one macroscopic object to another – an ensemble of 100 million rubidium atoms – with an accuracy approaching 90 percent. The human body, on the other hand, is comprised of some 1029 matter particles, all of which would have to be teleported with an extreme degree of precision.
There are other obstacles as well. As mentioned before, the object (or, in this case, person) being teleported will be destroyed at the sending station and reassembled at the receiving station. This could be painful for the traveler; however, the surviving copy is made before the original was destroyed, and so, from the point of view of our traveler – assuming that the traveler's conscience is transported with him – one could argue that no pain would ever be felt.
Moreover, a human traveler is not a static system, and so the process of scanning and reconstructing him or her must be nearly instantaneous – lest we end up with a teleported version of our telenaut that is dramatically different from the original.
One last consideration. At first, it would seem that quantum entanglement could hold the potential for travel at superluminal speeds: when two particles are entangled, no matter their distance, when we modify one particle, we also instantaneously modify the other. Unfortunately, all modern interpretations of quantum mechanics agree that this trick can't be used for faster-than-light travel.
Nobody expects to achieve human teleportation in the foreseeable future: it is an extraordinarily tough engineering problem, and even though the process wouldn't violate any fundamental law of physics, we lack the technology to achieve it – or anything even remotely close to it. In a sense, this piece of research could be seen as a small step toward human teleportation, but don't hold your breath for Star Trek-style teleporters just yet.
The study was published on the journal Physical Review Letters. An open-access version can be found here.


Quantum sensing exploits the properties of quantum mechanics to develop ultra-sensitive technology that can detect changes in electric and magnetic fields, and motion.
Image Credit: SkillUp/Shutterstock.com
A quantum object is characterized by its quantum mechanical behavior and properties. For example, the energy levels of a quantum object are quantized. This can be electronic, magnetic, or vibrational levels of atoms or molecules or spin states in superconductors. Another quantum characteristic is quantum coherence.
This describes the ability of the quantum states to maintain their wave-like superposition over time, withstanding any environmental interference. Quantum entanglement is also a quantum mechanical feature that describes a quantum object. Entanglement refers to generating two or more entangled particles that have identical quantum characteristics regardless of the distance between them.
What is Quantum Sensing?
Quantum sensing is achieved when a quantum object is used to measure a physical quantity. Any of the quantum properties described above can be implemented for detection. Changes in a physical quantity can be precisely measured by quantum coherence, quantum entanglement, or quantum states.
The physical parameter that a quantum sensor responds to will determine the type of quantum technology platform required. For example, trapped ions are sensitive to electric fields and will be an ideal probe for electric field detection. Spin-based quantum sensors respond primarily to magnetic fields. Some of the different quantum technology platforms and their applications in sensing are described below.
Spin properties of neutral alkali atoms in their ground state are used in quantum sensing. The requisite conditions required for sensing can be prepared and read out by lasers.
A thermal vapor of atoms at room temperature can be used as a magnetic probe. The Zeeman splitting of the atomic energy levels is used to detect weak magnetic fields. Magnetoencephalography (MEG) is a medical testing method that uses atomic vapor to measure magnetic fields produced by the brain's neural activity. In high-energy physics, atomic vapor-based sensing promises to enhance the detection of elementary particles.
Laser-cooled atoms that free-fall inside a vacuum tube are used in gravimetry. The matter-wave property of quantum particles is used to calculate acceleration by atom interferometry. The free-falling atoms are probed by lasers and the phase shift in the laser beam caused by the atoms is measured.
Gravimeters have the ability to detect gravity at a given location with very high sensitivity. An application where a gravity sensor has major implications is in construction projects. Infrastructure development is often delayed and costly because of unforeseen hidden features underground. Quantum gravimeters can detect risks early and assist in mitigating problems like sinkholes and mine shafts. Gravimeters can also be used to detect minerals and oils deep underground.
An accelerometer uses the same concept as a quantum gravimeter, for navigation. The ability to track minute changes in acceleration can provide information about the terrain and the environment. Quantum navigators do not rely on Global Positioning Systems (GPS) to steer towards a target.
Rydberg atoms are atoms that have absorbed energy to excite an electron to a higher, outer energy level. When the electron moves further from the nucleus of the atom, the strength of the atom’s polarization increases. This quality of Rydberg atoms makes them ideal quantum sensors for electric fields. Rydberg atoms have been successfully used as single microwave photon detectors. Rydberg atoms are also a popular candidate to simulate condensed matter systems due to their long-range interactions.
Atomic clocks use very insensitive electronic transitions in specific atoms to keep time with extreme accuracy. Optical clocks are used as the absolute frequency reference and have a significant impact in any application where timekeeping is essential. For example, in GPS, for high-speed broadband communications, and in the development of autonomous vehicles.
Electrical charge atomic ions trapped in eclectic or magnetic fields are also employed as quantum sensors. Laser-cooled motional states of trapped ions are extremely sensitive to electric fields and forces. Some advanced applications of trapped ions include ultrasensitive force microscopy, and detecting weak electric field noise above surfaces induced by absorbents. Trapped ions are also being explored as atomic clocks and as Rydberg ions.
In the field of optomechanics, quantized mechanical vibrations coupled to light can detect weak forces. Apart from force measurements, optomechanical sensing applications include acceleration, magnetic fields, voltages, masses and spins.
Quantum sensing is also achieved with photons, which are fundamental particles of light. Squeezed light, which produces partially entangled photons with quantum fluctuations below the shot noise limit, is used for extremely sensitive sensing applications. For example, the Laser Interferometer Gravitational-Wave Observatory (LIGO), employs squeezed light to detect gravitational waves.
Nuclear magnetic resonance (NMR)
Nuclear magnetic resonance (NMR) uses intrinsic spin properties of atomic nuclei to detect weak magnetic fields. NMR is one of the earliest quantum sensors to be commercialized. They have broad applications in clinical magnetic resonance imaging (MRI), geological and archaeological surveys, and space missions. NMR devices are sturdy and easy to operate.
Defects in Diamond
Color centers in diamond is another magnetic quantum sensor that has gained a wide range of applicability over the last decade. Electronic defects, fabricated in diamond crystals can be operated at room temperature with low-cost laser sources. Defects can be synthesized by injecting nitrogen, silicon, germanium, and other atoms into the diamond lattice. Microscopic mapping of magnetic fields enabled by nitrogen-vacancy centers in diamond (NV center) has led to imaging of magnetic organelles in bacteria, microscopic responses in meteorites as well Covid-19 diagnosis devices.
The Superconducting Quantum Interference Device (SQUIDs) is a very sensitive magnetometer. Built with superconducting interferometers, SQUIDs are one of the oldest quantum sensors. SQUIDs have been successfully used for materials characterization and clinical magnetoencephalography.
Quantum sensing has significantly advanced sensing technology in the last few years as highlighted in the examples above. With many government entities and private sectors accelerating quantum technology research and development, applications of quantum sensing will broaden and mature in the future. Other quantum mechanics-based device explorations in computing, simulation, and communications will have a profound impact on the growth of quantum sensing.
More from AZoQuantum: What is Quantum Chemistry?
References and Further Reading
C. L. Degen, F. Reinhard, and P. Cappellaro, Quantum sensing, Rev. Mod. Phys. 89, 035002 – Published 25 July 2017 DOI:https://doi.org/10.1103/RevModPhys.89.035002
Mahiro Abe et al, Matter-wave Atomic Gradiometer Interferometric Sensor (MAGIS-100), Quantum Sci. Technol. 6 044003, 2021 https://doi.org/10.1088/2058-9565/abf719
Barzanjeh, S., Xuereb, A., Gröblacher, S. et al. Optomechanics for quantum technologies.Nat. Phys. 18, 15–24 (2022). https://doi.org/10.1038/s41567-021-01402-0


Teleportation is the transfer of matter or energy from one location to another without either of them crossing the distance in the traditional physical sense. When Captain James T. Kirk of the "Star Trek" TV series and movies first told Starship Enterprise engineer, Montgomery "Scotty" Scott to "beam me up" in 1967, little did the actors know that by 1993, IBM scientist Charles H. Bennett and colleagues would propose a scientific theory that suggested the real-life possibility of teleportation.
By 1998, teleportation became reality when physicists at the California Institute of Technology quantum-teleported a particle of light from one location to another in a lab without it physically crossing the distance between the two locations. While some similarities do exist between science fiction and science fact, the teleportation in the real world differs greatly from its fictional roots.
Teleportation Roots: Quantum Physics and Mechanics
The branch of science that led to that first teleportation in 1998 gets its roots from the father of quantum mechanics, German physicist Max Planck. His work in 1900 and 1905 in thermodynamics led him to the discovery of distinct packets of energy he called "quanta." In his theory, now known as Planck's constant, he developed a formula that describes how quanta, at a subatomic level, perform as both particles and waves.
Many rules and principles in quantum mechanics at the macroscopic level describe these two types of occurrences: the dual existence of waves and particles. Particles, being localized experiences, convey both mass and energy in movement. Waves, representing delocalized events, spread across space-time, such as light waves in the electromagnetic spectrum, and carry energy but not mass as they move. For example, the balls on a pool table – objects that you can touch – behave like particles, while ripples on a pond behave like waves where there is "no net transport of water: hence no net transport of mass," writes Stephen Jenkins, physics professor at the University of Exeter in the U.K.
Fundamental Rule: Heisenberg's Uncertainty Principle
One fundamental rule of the universe, developed by Werner Heisenberg in 1927, now known as Heisenberg's uncertainty principle, says that there exists an intrinsic doubt affiliated with knowing the exact location and thrust of any individual particle. The more you can measure one of the particle's attributes, such as thrust, the more unclear the information about the particle's location becomes. In other words, the principle says you can't know both states of the particle at the same time, much less know the multiple states of many particles at once. On its own, Heisenberg's uncertainty principle makes the idea of teleportation impossible. But this is where quantum mechanics gets weird, and it's due to physicist Erwin Schrödinger's study of quantum entanglement.
Spooky Action at a Distance and Schrödinger's Cat
When summarized in the simplest of terms, quantum entanglement, which Einstein called "spooky action at a distance," essentially says that measurement of one entangled particle affects the measurement of the second entangled particle even if there's a wide distance between the two particles.
Schrödinger described this phenomenon in 1935 as a "departure from classical lines of thought" and published it in a two-part paper in which he called the theory "Verschränkung," or entanglement. In that paper, in which he also spoke of his paradoxical cat – alive and dead at the same time until observation collapsed the existence of the cat's state into it being either dead or alive – Schrödinger suggested that when two separate quantum systems become entangled or quantumly linked because of a previous encounter, an explanation of the features of one quantum system or state is not possible if it does not include the characteristics of the other system, no matter the spatial distance between the two systems.
Quantum entanglement forms the basis of quantum teleportation experiments scientists conduct today.
Quantum Teleportation and Science Fiction
Teleportation by scientists today relies upon quantum entanglement, so that what happens to one particle happens to the other instantaneously. Unlike science fiction, it doesn't involve physically scanning an object or a person and transmitting it to another location, because it's currently impossible to create a precise quantum copy of the original object or person without destroying the original.
Instead, quantum teleportation represents moving a quantum state (like information) from one atom to a different atom across a considerable difference. Scientific teams from the University of Michigan and the Joint Quantum Institute at the University of Maryland reported in 2009 that they successfully completed this particular experiment. In their experiment, information from one atom moved to another a meter apart. Scientists held each atom in separate enclosures during the experiment.
What the Future Holds for Teleportation
While the idea of transporting a person or an object from the Earth to a distant location in space remains in the realm of science fiction for the moment, quantum teleportation of data from one atom to another has potential for applications in multiple arenas: computers, cybersecurity, the Internet and more.
Basically any system that relies on transmitting data from one location to another could see data transmissions occur much faster than people can begin to imagine. When quantum teleportation results in data moving from one location to another without any time lapse because of superposition – the data existing in both the dual states of both 0 and 1 in a computer's binary system until measurement collapses the state into 0 or 1 – data moves faster than the speed of light. When this happens, computer technology will undergo a whole new revolution.
- Analog: Science Fiction and Fact Magazine: All About Teleportation
- Law and Business Review of the Americas: Telephonic Credit: The Next Generation of Branchless Banking in Mexico
- California Institute of Technology: Caltech Physicists Achieve First Bona-fide Quantum Teleportation
- University of Nebraska: Some Basic Ideas About Quantum Mechanics
- University of Pittsburgh: Einstein on the Completeness of Quantum Theory
- Stanford Encyclopedia of Philosophy: Quantum Entanglement and Information
- University of Maryland: Joint Quantum Institute: First Teleportation Between Distant Atoms
- Florida State University: Max Planck
About the Author
As a journalist and editor for several years, Laurie Brenner has covered many topics in her writings, but science is one of her first loves. Her stint as Manager of the California State Mining and Mineral Museum in California's gold country served to deepen her interest in science which she now fulfills by writing for online science websites. Brenner is also a published sci-fi author. She graduated from San Diego's Coleman College in 1972.


The years 2020 and 2021 have changed the way we look at our workplaces. Digital and remote work has become much more prominent while the concept of physical workplaces has started to demand a rethink. It was said that major pipelines of the economy would migrate to the digital environment and the need for Artificial Intelligence and related technology would become much more important than ever before.
As we stroll along a technological roadmap, the need as well as the demand for AI courses increases. When we look at applied AI courses, Google reviews suggest that such courses would reach the pinnacle of their popularity in the next five years.
That said, artificial intelligence has reinvented itself as a technology in the post-pandemic era. It is now used for vaccine trials as well as vaccine development and treatment of various diseases and ailments. Autonomous driving or self-driving cars that ferry only a single passenger due to covid 19 restrictions and advanced chatbot technology that caters to the grievances of customers are recent highlights of AI technology.
Let us understand such post-pandemic developments in artificial intelligence in some more detail.
How did AI fast-tracked the development of new vaccines?
Vaccine development is a very long process and takes many years to complete. There are usually three stages to vaccine development. Each stage takes no less than a year to get completed. However, with the help of artificial intelligence technology, we were able to analyse large data sets about Coronavirus from different countries of the world. With the help of artificial intelligence models, it also became possible to fast-track the process of data examination and vaccine trials from different countries of the world. In addition to this, artificial intelligence models also made the analysis of the sub-components or the proteins of the virus possible in a short span of time. The application of artificial intelligence technology in the genetic domain made it possible to create vaccines within one year of the first reported case of Coronavirus.
When we look at the technical aspects of artificial intelligence technology, we understand the relevance of the linear fold AI algorithm that proved very handy for medical teams around the globe to examine the sequence of ribonucleic acids. The linear fold algorithm made it possible to examine and predict the secondary structure of the ribonucleic acids as well as the possible mutation that it undergoes. With the help of this algorithm, we were also able to predict the human immune response that would be generated on exposure of the human body to the inactivated virus. This reduced the time span between the development of the virus and its approval by the regulating bodies.
How self-driving cars become the new normal for ferrying passengers in covid restrictions?
Although the technology of autonomous vehicles was already under development for the last five years, it found a great fit with the situation created by the Covid 19 virus. Passengers needed to be ferried from one place to another and driverless cars proved to be the perfect mode of transportation for doing this without any chance of infection from another person.
When we look at the technical aspects of driverless cars, we find that artificial intelligence has been able to conceive a reinforcement learning system within the vehicle that is able to learn from the environment so that the driving experience can be improvised in the long run. With the help of artificial intelligence, the safety aspects of the vehicle have also been addressed. It has become possible to connect the driverless car with the internet of things as well as satellite technology so that multiple safety levels can be created. The vehicle can also make a sense of the traffic up to a few kilometres and plan the ride accordingly. It is also possible to create a safety factor on the upper driving limit of the vehicle.
In addition to this, new innovations in the form of a 5G remote driving service are in the final stage of testing. Furthermore, we have also seen the commercialisation of the technology of self-driving vehicles in Singapore as well as China. The Apollo go Robo taxi service has been launched in several cities in China and trial operations have concluded successfully. This is a positive sign for conceiving a full-fledged fleet of Robo taxis in the time to come.
How has the advancement in chatbot technology led to an effective grievance redressal mechanism?
In the post-pandemic era, there has been a renewed impetus for chatbot technology. The artificial intelligence technology that operates behind a chatbot is natural language processing. With the help of Natural Language Processing, we are able to analyse the various aspects of human language like intent as well as emotions. In addition to this, natural language processing technology is able to power the most sophisticated chatbots that can be used for communication with humans through digital channels. This technology is extremely important in various industries that interact with customers through a digital interface. The business process outsourcing industry, as well as the telecommunication industry, are the most important industries where chatbot technology finds its application.
Since the Covid 19 virus, there have been constant innovations in chatbot technology as well as Natural Language Processing. The aim is to conceive the next generation of chatbots and virtual assistants that can communicate with humans by understanding sentiments, emotions and even linguistic patterns. One of the most important breakthroughs has come in the form of a novel framework for natural language generation called ERNIE-GEN. With the help of semantic modelling techniques that are used by ERNIE-GEN, it has become possible to maintain a human-like flow in dialogue engagement and question generation.
How has the field of quantum computing witnessed significant advances with AI technology?
Quantum computing has been our answer to the most complex computational tasks and the derivation of their solutions in a short span of time. This technology makes use of qubits that can simultaneously hold both values of zero and one and is a huge advancement over the erstwhile binary technology that we followed in computing operations. With the help of quantum computing technology, we have been able to process the largest amount of information possible and run various cloud processes simultaneously in real-time.
Deep learning algorithms have played a great role in the advancement of quantum computing research. The next level of quantum computing would become possible once this technology is integrated with artificial intelligence. One example of this is the launch of paddle quantum which allows researchers to train Quantum neural networks with a lot of ease.
In addition to this, we may witness further development in the field of Quantum computing as researchers line up to launch Quantum leaf. Quantum leaf provides such a type of development toolkit to researchers that can enable them to work in cloud-based Quantum computing ecosystems and also reduce the time span of quantum programming.
Further innovation would be seen in the form of artificial intelligence devices like artificial intelligence chips that would be designed to perform specific tasks. A large number of companies have already started to make major breakthroughs in AI technology and further innovations and developments are in the pipeline.


In 2020, a star system close to Earth made headlines when it was discovered to host a black hole, but further investigations have revealed something much rarer dwelling in the system.
Image Credit: alionaprof/Shutterstock.com
Back in 2020, astronomers believed they had made a startling discovery lurking in Earth’s cosmic backyard. Using the FEROS spectrograph on the MPG/ESO 2.2 meter telescope located at the La Silla observatory in the Chilean desert, a team including researchers from the European Southern Observatory (ESO) believed they had found a black hole in the system HR 6819, located within the Milky Way.
At a distance of just 1000 light-years from Earth, this would have made the black hole in HR 6819 the closest such object to Earth. So close in fact, that its host system can be seen with the naked eye.
It would have also meant that the star system HR 6819 was a triple system consisting of two stars and a black hole.
The discovery of the triple system with two stars and the invisible black hole was a complete surprise to astronomers when the research was published in a paper in the journal Astronomy & Astrophysics.
However, not everyone was completely satisfied with the result. Another team of researchers set about testing if HR 6819 was indeed a triple system with a black hole.
This team was joined by the initial team of astronomers keen to challenge their own results in what would prove to be a validation of the never-ending curiosity and drive for answers in science and those that practice it.
Indeed, these researchers would discover that HR 6819’s black hole is absent. It was never really there at all. But, in its place is something rarer, a most extraordinary cosmic vampire — a star bloated after feeding from its companion.
Astronomers Go Vampire Hunting
Upon the close study of the HR 6819 system in 2020, astronomers were left with two competing and contradictory theories. There were two sources of light in the system orbiting each other
Because this implies a third, dark body, purely supplying a source of gravity for one of the two luminous stars to orbit around — namely a black hole — authors of the Astronomy & Astrophysics paper and ESO astronomers Thomas Rivinius and Dietrich Baade believed what they had discovered was a triple system with a black hole.
However, the researchers couldn’t rule out a binary system with an unusual star caught in a very brief, and thus extremely rare, phase after an interaction with its companion stripped it of stellar material.
If the black hole scenario were true, the stars in the triple system version of HR 6819 should be far apart, whereas if the rare binary scenario was correct, the two stars should be closer together with no invisible interloper between them.
Thus, the key to solving this conundrum was obtaining a clearer picture of HR 6819. Joined by ESO fellow Julia Bodensteiner and her team, the original researchers set about doing this by studying the mysterious system with ESO’s Very Large Telescope (VLT) and Very Large Telescope Interferometer (VLTI).
Using these instruments, the team was able to determine that the stars are close together, orbiting each other in just a 40-day orbit period.
This may initially seem disappointing, but the lack of a black hole makes HR 6819 no less fascinating. In fact, the astronomers discovered that one of the stars must have recently ‘fed’ upon the stellar material of the other, causing it to lose a large amount of mass — almost all of it in fact.
A Rare And Short-Lived Cosmic Vampire
Observing stars stripping material from a companion donor star is not uncommon, but the stage that follows this mass transfer is much tougher to spot.
Following the loss of much of its material, the donor star quickly shrinks to become a very small and hot subdwarf. What the team observed in HR 6819 is a star that has lost a great deal of material but has yet to shrink to this state. This means that the mass loss must have occurred in the system’s recent history.
This presents a unique opportunity for astronomers - a short window of time to observe the inner layers of a star after the outer layers have been stripped away. This short-lived and rare phase could reveal the history of the system and help researchers better understand what happens when one star feeds upon another.
According to a recent and updated paper published in Astronomy & Astrophysics, all this means that the current best estimation of HD 6819 is that it is a binary system with no black hole in which two stars have interacted, with the stripping of mass from one star speeding it up like a spinning top.
Astronomers have caught these stars in a rare phase of existence, meaning that not only could further investigations reveal more secrets buried in the binary, but could teach us about the evolution of binary stars.
More from AZoQuantum: The Role of Diamonds in Quantum Computing
References and Further Reading
Rivinius. T.H, Baade. D, Hadrava. P, Heida. M, Klement. R, , ‘A naked-eye triple system with a non-accreting black hole in the inner binary,’ Astronomy and Astrophysics, [DOI: 10.1051/0004–6361/202038020]
Frost. A.J., Bodensteiner. J., Baade. D., et al, , ‘HR 6819 is a binary system with no black hole,’ Astronomy & Astrophysics, https://www.aanda.org/articles/aa/full_html/2022/03/aa43004-21/aa43004-21.html


Graphene is the super substance that could replace silicon, plastic and glass
By Marco Chiappetta
The silicon, plastic, and glass that make up much of our tech these days could soon be replaced with something old, yet completely new: Graphene.
If graphene sounds like something that could fell a superhero, you’re almost right. It’s the thinnest substance known to science, yet it’s 300 times stronger than steel and harder than a diamond. High-quality graphene is also transparent and flexible, and it’s an excellent conductor of heat and electricity.
We’ve known of graphene’s existence since the mid-1800s, but scientists have been able to experiment with graphene only in the past decade. In 2004, two researchers at the University of Manchester isolated graphene for the very first time, using—believe it or not—a chunk of graphite and a roll of adhesive tape.
So what exactly is graphene?
Graphene is a crystalline structure composed entirely of carbon atoms, arranged in a hexagonal, honeycomb-like pattern. Graphene’s single-atom thinness (meaning it has length and width, but no height) makes it as close to 2D as any substance can be.
Graphene is also a fundamental component of other allotropes (structurally different forms of the element carbon). These include charcoal, carbon nanotubes, and other fullerenes (molecules composed solely of carbon).
It is graphene’s unique structure and composition that endows it with so many valuable properties. Carbon atoms have four electrons in their outer shell, three of which form strong covalent bonds with the electrons in neighboring carbon atoms. This gives graphene its signature hexagonal shape. The fourth electron in each carbon atom, now known to be fermions, behave like relativistic particles described by the Dirac equation (which, in another sci-fi twist, also implies the existence of antimatter).
Getting back to graphene, it is those free electrons, in conjunction with the material’s relative uniformity, that make graphene such an excellent electrical and thermal conductor, superior to copper and silver respectively. The strong covalent bonds between the carbon atoms, meanwhile, give graphene its strength.
Layers of graphene are bonded by weak van der Waals forces (the sum of attractive forces between two surfaces, accounting for a lizard’s ability to climb vertical walls, among other things). The bonds between the carbon atoms in each layer of graphene, on the other hand, are incredibly strong; in fact, a hammock fabricated from a single-atom-thick sheet of graphene could support a load of nearly 9 pounds.
High-quality graphene is also lightweight, flexible, impermeable to other elements, and it’s virtually transparent. Thanks to the space between its atoms, the material absorbs just 2.3 percent of white light, allowing 97 percent to pass through.
How graphene might be used
Potential applications for graphene are nearly limitless. Numerous projects are already underway in industries ranging from consumer electronics to sporting goods. To date, graphene-based consumer products have been limited to items that use a small amount of the substance in protective coatings. Once the mysteries of graphene manufacturing have been unlocked—more on that later—you can expect to find the material everywhere.
One area where graphene is likely to have the most immediate impact is the manufacture of flexible and transparent electronics, such as touchscreens. Graphene could replace indium, which is one of the rarest elements on Earth. (Carbon—the foundation of graphene—is one of the most abundant elements on the planet.) Graphene is also lighter, thinner, and stronger than indium. Ultra-strong windshields that double as display clusters are not out of the realm of possibility. Neither is Tony Stark’s transparent smartphone.
Graphene’s electrical properties also render it an ideal material for building integrated circuits. During a Q&A session at the 2013 Intel Developers Forum, Intel CEO Brian Krzanich said the company is evaluating graphene’s potential use in chip manufacturing, replacing silicon. Routine use, he said, would be a “few generations” out, putting it roughly in the 2020 timeframe.
Graphene might also serve as the foundation for next-generation solid-state capacitors that charge more quickly than today’s offerings and hold a charge for much longer. And graphene could usher in an age of ultra-powerful, lightweight batteries with far more capacity than anything available today. By super-cooling graphene and surrounding it in strong magnetic fields, researchers have also been able to alter the direction of the flow of electrons along graphene’s surface, based on the spin of the electrons, which opens up possibilities for quantum computing.
Graphene won’t be relegated solely to electronics and display technology. Its excellent strength-to-weight ratio could also pave the way for strong, lightweight vehicles, while its transparency and electrical conductivity make it a good candidate for future solar panels. Punching nano-sized holes in a sheet of otherwise impermeable graphene could be used in machines that pull a single strand of DNA through the hole, for rapid DNA sequencing, or water purification or desalination.
Before those fantastical devices can become reality, however, industry must first develop a reliable, cost-effective manufacturing process. That’s where the majority of current graphene research effort is concentrated.
Graphene is being manufactured today using a number of methods: The “Scotch tape” method (also known as mechanical exfoliation or the cleavage method), is the simplest. This is how Andre Geim and Konstantin Novoselov isolated graphene from a larger hunk of graphite in 2004—research that led to their being awarded the Nobel Prize in Physics in 2010.
The adhesive tape is used to extract small pieces of graphite from a larger chunk. A layer of graphene is peeled away from the graphite by continually folding the tape over the pieces and then separating the tape. The strength of the adhesive overcomes the weak van der Walls forces holding the layers of graphite together until there is a single layer, yielding graphene.
Mechanical exfoliation can be used only to isolate relatively small pieces of graphene, however, so researchers are experimenting with other methods to produce larger quantities.
Chemical vapor deposition (CVD) is one of the most promising. In this process, chemical vapors are evaporated in a furnace, leaving a graphene deposit on a thin metal substrate. A similar process has been used in the manufacture of very large integrated circuits (VLSI) for many years. Graphene can also be isolated by submerging graphite in a liquid and blasting it with ultrasonic waves to separate its individual layers, or by slicing an edge of a cylinder formed from graphene (also known as a carbon nanotube).
Using these methods, scientists have been able to produce pieces of graphene of various qualities and sizes, including long graphene strands that have already been used to make super-capacitors. While some companies—most recently Samsung—have claimed breakthrough achievements in graphene manufacturing, most of the known work remains academic and has not yet scaled to real-world industrial applications.
We’re still a ways off from widespread availability of graphene-based microprocessors, flexible touchscreens, and similarly exotic new devices. But when industry perfects a practical and inexpensive means of manufacturing graphene, you can bet it will become as ubiquitous as plastics are today.
Image credits: The image at the top of this page is courtesy of Graphenea, a graphene manufacturer and supplier. The image of the graphite, adhesive tape dispenser, and graphene transistors was released by the copyright holder into the public domain.
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Quantum mechanics is usually associated with weird and counterintuitive phenomena we can't observe in real life. But it turns out that quantum processes can occur in living organisms, too, and with very concrete consequences. Some species of birds, for example, use quantum mechanics to navigate. And as Plus found out at a conference on quantum physics and the nature of reality, which took place in Oxford in September, studying these little creatures' quantum compass may help us achieve the holy grail of computer science: building a quantum computer.
At the conference Plus editor Rachel Thomas met up with the physicists Simon Benjamin and Erik Gauger, both from the University of Oxford, who were intrigued by research done with European Robins by biologists in Frankfurt, Germany. European robins spend their summers in Scandinavia, but avoid the chilly winter by migrating to North Africa in the autumn. Biologists believe that the birds' sense of direction comes from an internal quantum compass in the bird's eye which consists of two electrons and a quantum property called spin. Effectively, each electron behaves like a tiny bar magnet, which can point either up or down. (For a more detailed explanation of electron spin read this entertaining blog by Chad Orzel, which includes a demonstration by his toddler!)
"The two electrons [in the bird compass] are correlated with each other, with their spins pointing in different directions, " explains Benjamin. "They get excited when a photon is absorbed in the bird's eye. The two electron spins then move apart from each other. The way they behave afterward, whether they stay correlated as they were originally, or the correlations change, depends on the Earth's magnetic field." Thus able to sense the Earth's magnetic field, the birds know which direction to fly in.
Biologists have known about this theoretical model of the birds' navigation system, called the radical-pair model, for around thirty years. It's quantum mechanical, since spin is a quantum mechanical concept, but not sufficiently so to interest hard-core quantum physicists like Benjamin and Gauger. What caught their interest was some recent research by Roswitha and Wolfgang Wiltschko, from the Goethe University, into how easily the birds' quantum compass could be disrupted.
To test the bird compass, the researchers had kidnapped some birds on their way down to North Africa and subjected them to a weak oscillatory electromagnetic field, that is a field whose strength jitters backwards and forwards about a million times a second. "That's an incredibly weak oscillatory field," says Benjamin. "Not only could it not possibly harm the birds, but it would be amazing if the birds could even tell that there was this [oscillation]."
Surprisingly, though, this weak signal was enough to disrupt the birds' sense of direction. "The researchers found that at a particular speed of oscillation — 1.3 MHz — suddenly the birds were no longer able to orientate themselves," says Benjamin. "The direction they wanted to go in became random, no longer pointing to Africa."
Intrigued that such a tiny perturbation should have an effect on the birds, Benjamin and Gauger looked at the mathematics describing what goes on in the birds' quantum compass. They were particularly interested to see how long it would take for the effect of the field to kick in, since basic physics suggests that detecting signals as weak as that takes some time. "There must be time for this tiny effect to build up and make a difference for the bird," says Benjamin. Using their equations Benjamin and Gauger calculated that it would take at least 120 microseconds for the birds' compass to get jammed by the field. That's very fast, certainly a time period like that can't be detected by humans, but in terms of quantum processes it's rather slow.
And this is where quantum computers come into to the picture. As the name suggests, quantum computers work using quantum processes. No-one has as yet been able to build a useful working quantum computer, but once we do, these machines will be way faster and more powerful than ordinary computers.
Electrons and their spins form the basic components of quantum computers. "In [quantum computing] you care about in which direction electron spins point and how they correlate with each other," says Benjamin. "But in order to make a quantum computer work , you must insulate these electron spins, the tiny magnets, from the rest of the world. For that reason people have been trying to come up with molecules that can protect electron spins, to isolate them from the rest of the world."
A nitrogen-doped C60 molecule — an atom of nitrogen trapped in a carbon cage. Image Quantum Spin Dynamics group at the University of Oxford.
What Benjamin and Gauger realised is that the same goes for the the birds. For the bird compass to work, interference from the outside world must be kept down to a very low level. "Otherwise it would mess up such a long lasting sensing process," says Benjamin. Since it takes the bird at least 120 microseconds to detect the oscillatory field, it must be able to insulate its quantum compass from the outside world for at least that length of time, perhaps more. That's compared to the record of 80 microseconds that's so far been achieved in the lab. "It seems that the way the bird protects the pair of two tiny magnets is better than the best we can do," says Benjamin.
What's more, the exotic molecule used to insulate quantum systems in the lab — a nitrogen atom trapped inside a carbon cage, called N@C60 — is incredibly hard to make (and costs around £7 million a gramme). The birds certainly don't have access to this material, so the question is how they achieve their insulation and if we can copy their method to build quantum computers. "It's a series of ifs," says Benjamin. "Various things could be wrong. The experimental results could be wrong, or our basic idea of [how the quantum compass works] might be wrong. But if all the ingredients are correct and there really is this extraordinary protection of quantum information in the birds, then it's conceivable that we can work out what chemical it is and we might learn a thing or two."
You can listen to the podcast of our interview with Simon and Erik, as well as our podcast from the conference on Quantum Physics and the Nature of Reality. You can also learn more about quantum mechanics from Simon in Caging Schrödinger's Cat, his series of audio and video podcasts about quantum nanotechnology.
What happens if you rear a robin in any other place where the temperature is uniformly comfortable all year? Does it still want to fly to Africa during a European winter?
Is this the same method used by all migratory birds and animals?
Everyone knows that pigeons carried small messages for ancient kings. Many assume that the same pigeon could be used between any two places. They can't.
The magnetic extractive properties unique to the place it was hatched in and bred for about a year get embedded within a pigeons body. Then you have to transport in its cage to say, a war front.
A message capsule fixed to its feet will be delivered by that pigeon only its place of birth.
It is as if it develops an invisible rubber band leash anchored to the first place.
Humans have a similar desire to die in the place of their births.
I think with humans it's more complex. If you have happy memories of many years spent at a place, then that becomes your rubber bands' anchor.


by Thomas Stace
The technology that allowed Marty McFly to travel back in time in the 1985 movie Back to the Future was the mythical flux capacitor, designed by inventor Doc Brown.
We’ve now developed our own kind of flux capacitor, as detailed recently in Physical Review Letters.
While we can’t send a DeLorean car back in time, we hope it will have important applications in communication technology and quantum computing.
How did we do it? Well it’s all to do with symmetry. There are many kinds of symmetry in science, including one that deals with time reversal.
Time reversal symmetry is a complex sort of symmetry that physicists like to think about, and relies on the imaginary as much as the real.
Suppose you make a movie of an event occurring. You could then ask: “If I edited the movie to run backwards, and showed it to my friends, could they tell?”
This might seem obvious: people don’t usually walk or talk backwards; spilt milk doesn’t spontaneously jump back into its carton; a golf ball doesn’t miraculously launch backwards from the fairway, landing perfectly balanced on the tee at the same moment as the club catches it.
Source: Tom Stace
But at a microscopic level, the story is not that clear. The collision of two billiard balls looks pretty similar in reverse; even more so for the collision of two atoms. A beam of light travelling in one direction obeys exactly the same laws of physics as a beam of light travelling in the opposite direction.
Indeed, the basic equations of physics look essentially the same if we replace time with its negative. This mathematical transformation reverses the flow of time in our equations.
Since the microscopic laws of physics appear to be unchanged under this mathematical transformation, we say the universe possesses time reversal symmetry, even though we cannot actually reverse time in reality. Unlike Doc Brown, we can’t make the clock tick backwards.
There is a conceptual conflict here. At the macroscopic scale, the entropy of the universe — a measure of disorder or randomness — always increases, so that there is an arrow of time.
This is obvious in our everyday experience: a scrambled egg is not reversible. How does this irreversiblity emerge from microscopic laws that are reversible? This remains a mystery.
The Circulator Circuit
Microscopic reversibility presents an important technological challenge. It complicates the diversion of electronic and radio signals around a circuit.
There are various applications where engineers want electromagnetic signals (such as light or radio waves) in a circuit to behave a bit like cars around a roundabout.
This is pictured below: a signal entering port A of the device should be directed to port B; a signal entering at B should go to port C; and a signal entering port Cshould be directed to port A, clockwise around the device.
One way to do this is to use a network of amplifiers to switch signals as desired. But there is a profound result in quantum mechanics (the “no cloning theorem”) that means that amplification must always add noise, or randomness, to the signal. Sorry audiophiles: a perfect amplifier is impossible.
If the signal is extremely weak, so that additional noise is intolerable, then noiseless circulation is accomplished with a device called a circulator. Such devices are used to separate very weak signals going to and from sensitive electronics, including in radar receivers, or in existing and future quantum computers.
It turns out a device like this must locally break time reversal symmetry. If we made a movie of the signals coming and going from the circulator, and ran the movie backwards, it would look different. For example, we would see a signal entering port B and leaving via port A, rather than via C.
But most devices in a quantum research laboratory, such as mirrors, beam splitters, lasers, atoms do not break time reversal symmetry, so cannot be used as circulators. Something else is needed.
The practical way to break time reversal symmetry for real devices is to introduce a magnetic field. Like a rotating vortex in water, magnetic fields have a circulation, since they arise from electrical currents circulating in an electrical loop.
The magnetic field defines a direction of rotation (clockwise or counterclockwise) for electrically charged particles and thus for electrical signals. So when physicists say that a device breaks time reversal symmetry, they usually mean that there is a magnetic field about somewhere.
Commercial circulators are an anomaly in the world of electronics. Unlike transistors, diodes, capacitors and other circuit elements, basic materials science means that commercial circulators have not been miniaturised, and are still the size of a coin.
Building them into large-scale integrated microelectronic circuits is therefore a challenge. This will become an increasing problem as we try to fit thousands of qubits on a quantum computer chip, each requiring its own circulator to enable control and read-out.
Our Quantum Flux Capacitor
We have developed a new way of building micrometer-sized circulators that can be fabricated on a microchip.
We figured out how to integrate magnetic flux quanta — the smallest units of magnetic field — with microfabricated capacitors and other superconducting circuit elements, so that time-reversal symmetry can be broken.
This lead to our new circulator proposal. As with conventional circulators, there is a magnetic field present. But because we can use just one magnetic flux quantum, our design can be microscopic.
Sadly for history buffs, our design won’t help much in your DeLorean time machine: it doesn’t reverse time. But its magnetic field does break time-reversal symmetry as advertised and we expect these devices will find applications in future quantum technologies.
Even sooner, they may help in high-bandwidth communications environments like mobile phone base stations in very dense populations, or for ultra-high sensitivity radar where every photon of the electromagnetic field counts.
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Researchers at the Department of Energy’s Oak Ridge National Laboratory have developed a quantum chemistry simulation benchmark to evaluate the performance of quantum devices and guide the development of applications for future quantum computers.
Their findings were published in npj Quantum Information.
Quantum computers use the laws of quantum mechanics and units known as qubits to greatly increase the threshold at which information can be transmitted and processed. Whereas traditional “bits” have a value of either 0 or 1, qubits are encoded with values of both 0 and 1, or any combination thereof, allowing for a vast number of possibilities for storing data.
While still in their early stages, quantum systems have the potential to be exponentially more powerful than today’s leading classical computing systems and promise to revolutionize research in materials, chemistry, high-energy physics, and across the scientific spectrum.
But because these systems are in their relative infancy, understanding what applications are well suited to their unique architectures is considered an important field of research.
“We are currently running fairly simple scientific problems that represent the sort of problems we believe these systems will help us to solve in the future,” said ORNL’s Raphael Pooser, principal investigator of the Quantum Testbed Pathfinder project. “These benchmarks give us an idea of how future quantum systems will perform when tackling similar, though exponentially more complex, simulations.”
Pooser and his colleagues calculated the bound state energy of alkali hydride molecules on 20-qubit IBM Tokyo and 16-qubit Rigetti Aspen processors. These molecules are simple and their energies well understood, allowing them to effectively test the performance of the quantum computer.
By tuning the quantum computer as a function of a few parameters, the team calculated these molecules’ bound states with chemical accuracy, which was obtained using simulations on a classical computer. Of equal importance is the fact that the quantum calculations also included systematic error mitigation, illuminating the shortcomings in current quantum hardware.
Systematic error occurs when the “noise” inherent in current quantum architectures affects their operation. Because quantum computers are extremely delicate (for instance, the qubits used by the ORNL team are kept in a dilution refrigerator at around 20 millikelvin (or more than -450 degrees Fahrenheit), temperatures and vibrations from their surrounding environments can create instabilities that throw off their accuracy. For instance, such noise may cause a qubit to rotate 21 degrees instead of the desired 20, greatly affecting a calculation’s outcome.
“This new benchmark characterizes the ‘mixed state,’ or how the environment and machine interact, very well,” Pooser said. “This work is a critical step toward a universal benchmark to measure the performance of quantum computers, much like the LINPACK metric is used to judge the fastest classical computers in the world.”
While the calculations were fairly simple compared to what is possible on leading classical systems such as ORNL’s Summit, currently ranked as the world’s most powerful computer, quantum chemistry, along with nuclear physics and quantum field theory, is considered a quantum “killer app.” In other words, it is believed that as they evolve quantum computers will be able to more accurately and more efficiently perform a wide swathe of chemistry-related calculations better than any classical computer currently in operation, including Summit.
“The current benchmark is a first step towards a comprehensive suite of benchmarks and metrics that govern the performance of quantum processors for different science domains,” said ORNL quantum chemist Jacek Jakowski. “We expect it to evolve with time as the quantum computing hardware improves. ORNL’s vast expertise in domain sciences, computer science and high-performance computing make it the perfect venue for the creation of this benchmark suite.”
ORNL has been planning for paradigm-shifting platforms such as quantum for more than a decade via dedicated research programs in quantum computing, networking, sensing and quantum materials. These efforts aim to accelerate the understanding of how near-term quantum computing resources can help tackle today’s most daunting scientific challenges and support the recently announced National Quantum Initiative, a federal effort to ensure American leadership in quantum sciences, particularly computing.
Such leadership will require systems like Summit to ensure the steady march from devices such as those used by the ORNL team to larger-scale quantum systems exponentially more powerful than anything in operation today.
Access to the IBM and Rigetti processors was provided by the Quantum Computing User Program at the Oak Ridge Leadership Computing Facility, which provides early access to existing, commercial quantum computing systems while supporting the development of future quantum programmers through educational outreach and internship programs. Support for the research came from DOE’s Office of Science Advanced Scientific Computing Research program.
“This project helps DOE better understand what will work and what won’t work as they forge ahead in their mission to realize the potential of quantum computing in solving today’s biggest science and national security challenges,” Pooser said.
Next, the team plans to calculate the exponentially more complex excited states of these molecules, which will help them devise further novel error mitigation schemes and bring the possibility of practical quantum computing one step closer to reality.
Read more from original source: https://www.eurekalert.org/pub_releases/2020-01/drnl-ora010220


CHICAGO: Flashes of what may become a transformative new technology are coursing through a network of optic fibres under Chicago.
Researchers have created one of the world’s largest – a field of science that depends on paradoxes so strange that Albert Einstein didn’t believe them.
The network, which connects the University of Chicago with Argonne National Laboratory in Lemont, is a rudimentary version of what scientists hope someday to become the. For now, it’s opened up to businesses and researchers to test fundamentals of quantum information sharing.
The network was announced this week by the Chicago Quantum Exchange – which also involves Fermi National Accelerator Laboratory, Northwestern University, the University of Illinois and the University of Wisconsin.
With a US$500mil (RM2.2 trillion) federal investment in recent years and US$200mil (RM880mil) from the state, Chicago, Urbana-Champaign, and Madison form a leading region for quantum information research.
Why does this matter to the average person? Because quantum information has the potential to help crack currently unsolvable problems, both threaten and protect private information, and lead to breakthroughs in agriculture, medicine and climate change.
While classical computing uses bits of information containing either a 1 or zero, quantum bits, or qubits, are like a coin flipped in the air – they contain both a 1 and zero, to be determined once it’s observed.
That quality of being in two or more states at once, called superposition, is one of the many paradoxes of quantum mechanics – how particles behave at the atomic and subatomic level. It’s also a potentially crucial advantage, because it can handle exponentially more complex problems.
Another key aspect is the property of entanglement, in which qubits separated by great distances can still be correlated, so a measurement in one place reveals a measurement far away.
The newly expanded Chicago network, created in collaboration with Toshiba, distributes particles of light, called photons. Trying to intercept the photons destroys them and the information they contain – making it far more difficult to
The new network allows researchers to “push the boundaries of what is currently possible,” said University of Chicago professor David Awschalom, director of the Chicago Quantum Exchange.
However, researchers must solve many practical problems before large-scale quantum computing and networking are possible.
For instance, researchers at Argonne are working on creating a “foundry” where dependable qubits could be forged. One example is a with tiny pockets to hold and process qubits of information. Researchers at Argonne also have by freezing neon to hold a single electron.
Because quantum phenomena are extremely sensitive to any disturbance, they might also be used as tiny sensors for medical or other applications – but they’d also have to be made more durable.
The quantum network was launched at Argonne in 2020, but has now expanded to Hyde Park and opened for use by businesses and researchers to test new communication devices, security protocols and algorithms. Any venture that depends on secure information, such as banks’ financial records of hospital medical records, would potentially use such a system.
Quantum computers, while in development now, may someday be able to perform far more complex calculations than current computers, such as, which could be useful in developing drugs to treat diseases such as Alzheimer’s.
In addition to driving research, the quantum field is stimulating economic development in the region. A hardware company, EeroQ, announced in January that it’s moving its headquarters to Chicago. Another local software company,, was recently acquired, and several others are starting up in the region.
Because quantum computing could be used to hack into traditional encryption, it has also attracted the bipartisan attention of federal lawmakers. The National Quantum Initiative Act was signed into law by President Donald Trump in 2018 to accelerate quantum development for national security purposes.
In May, President Joe Biden directed federal agency to migrate to quantum-resistant cryptography on its most critical defence and intelligence systems.
Ironically, basic mathematical problems, such as 5+5=10, are somewhat difficult through quantum computing. Quantum information is likely to be used for high-end applications, while classical computing will likely continueto be practical for many daily uses.
Renowned physicist Einstein famously scoffed at the paradoxes and uncertainties of quantum mechanics, saying that God does not “play dice” with the universe. But quantum theories have been proven correct in applications from nuclear energy to MRIs.
Stephen Gray, senior scientist at Argonne, who works on algorithms to run on quantum computers, said quantum work is very difficult, and that no one understands it fully.
But there have been significant developments in the field over the past 30 years, leading to what some scientists jokingly called Quantum 2.0, with practical advances expected over the next decade.
“We’re betting in the next five to 10 years there’ll be a true quantum advantage (over classical computing),” Gray said. “We’re not there yet. Some naysayers shake their canes and say it’s never going to happen. But we’re positive.”
Just as early work on conventional computers eventually led to cellphones, it’s hard to predict where quantum research will lead, said Brian DeMarco, professor of physics at the University of Illinois at Urbana-Champaign, who works with the Chicago Quantum Exchange.
“That’s why it’s an exciting time,” he said. “The most important applications are yet to be discovered.” – Chicago Tribune/dpa