SANTA FE, N.M. Researchers at Los Alamos National Laboratories claim to have originated a blueprint for room-temperature quantum computers using such optical components as beam splitters, phase shifters and photodetectors. While some scientists contend that new kinds of nonlinear optical components must be invented before economical quantum computers can be realized, the Los Alamos team counters that artful use of feedback makes it possible to use existing optical components instead.
The new approach, currently at the simulation stage, suggests that a more practical route can be followed to build effective quantum computers. Current methods use bulky and expensive equipment such as nuclear magnetic-resonance imaging systems, and the quantum states used to encode quantum bits, or "qubits,"are maintained at temperatures close to absolute zero.
However, at room temperature, photons exhibit quantum behavior, and a lot of known technology can manipulate them. "The double-slit experiment, where a single photon goes through whichever parallel slit you put a photodetector behind, clearly demonstrates the quantum-mechanical aspects of photons," said Los Alamos National Laboratories researcher Emanuel Knill. "Others thought you needed a new kind of nonlinear optical component to make quantum computers with photons. We have shown that all you need is feedback."
Knill's work was done with another Los Alamos researcher, Raymond Laflamme, and with professor Gerard Milburn of the University of Queensland, St. Lucia, Australia.
Photons can act as the data in quantum computers by virtue of their dual wave/particle nature. The famous double-slit experiment sends a single photon toward two parallel slits and locates a single photodetector behind first one slit and then the other. No matter which slit the photodetector is put behind, it always detects the single photon.
How does the photon "know"which slit to go through? The answer is that it is acting as a wave instead of a particle, and thus goes through both until it is measured by the photodetector. The act of measurement instantaneously localizes the "particle" aspect of the photon essentially causing it to "condense" behind whichever slit the measurement is made.
For the optical quantum computer blueprint provided by the labs, the phase state as polarized either vertically or horizontally works off the ability of photons to represent 1s and 0s. With all quantum bits, the phase of a photon's wave can simultaneously represent both 1 and 0, since its phase can differ depending on the exact moment it is measured. Afterward that is no longer possible; the phase has become fixed as one or the other by the very act of measurement.
"Until our work, it was thought that the only way to get photons to interact with each other was with nonlinear optics, which is very difficult to implement,"said Knill. "Nonlinear media work fine if you send laser beams through them, but if you only send single photons through, essentially nothing happens."
To provide the necessary nonlinear coupling among qubits, using photons, the team of Knill, Laflamme and Milburn fell back on one of the most useful engineering techniques ever invented feedback.
By employing feedback from the outputs of the photodetectors, they were able to simulate the effect of nonlinear media without the disadvantages of actually using them. Essentially, the optical components capable of handling single photons were bent to the service of nonlinear couplings through feedback.
"People never thought to use feedback from the result of a photodetector, but that is where our nonlinearity comes from it was there all along," Knill explained. This technique was not tried because researchers assumed they could not reuse measurements in quantum computations.
"We discovered that you can use feedback, and that you can replace a nonlinear component with it," said Laflamme.
As in all quantum-mechanical systems, the most important principle has been to preserve "coherence" that is, to make sure that the qubits remain "unobserved" in their nebulous superposition of both 1 and 0 during a calculation. Once a measurement is made of a quantum-mechanical state, the system reverts to a normal digital system and the advantage of quantum computations is lost. That was why it was thought that feedback could not work because it would destroy the quantum coherence that forms the basis for quantum algorithms.
However, Knill, Laflamme and Milburn have shown that systems that combine qubits with ordinary bits in the feedback loop can simulate nonlinear optical components. "What we do essentially is destroy coherence in one place and manage to indirectly reintroduce it elsewhere so that only the coherence we don't care about gets lost in the measurement," said Knill.
The basic idea is that the original qubits to be used in a calculation can be prepared ahead of time by entangling them with what the researchers call "helper" qubits. Entangling ensures that the helper bits maintain the same state as the originals, even after they have gone through a quantum calculation. The helper qubits can then be independently processed with standard optical components, and after the calculation, they can be measured without destroying the coherence of the originals.
The results of measuring the helper qubits are introduced into the feedback loop, which then simulates a nonlinear optical component for a single photon. There is a price for the destroyed coherence of the helper bits, however. According to the researchers, the labs' quantum computer blueprint will make more errors than the already error-prone quantum computers designed elsewhere. To compensate, the team carefully architected their design to use built-in error correction in two subsequent stages.
"The most important discovery in quantum computing in the last five years has been quantum error correction," said Laflamme. "Using quantum error correction, we can mitigate the effect of the errors we introduce with our measurements."
The resulting architecture uses three distinct stages. In stage one, helper photons are generated by entanglement and teleported to a circuit running in parallel with the main calculation. Measurement of the helper bits, after the main calculation, is then introduced into the feedback loop to simulate the effect of a nonlinear coupling between two photons.
"We know when it succeeds by measuring the helper qubit. If the outcome is good, then we go on with whatever else we are going to do in the calculations, but if it fails then we forget about what we just did and start over," said Knill.
But calculations made in this way are successful only with a quantum probability of 1/4, which necessitates the second stage of the architecture.
In stage two, the success probability of stage one can be tuned arbitrarily close to 1. Unfortunately, however, the computing resources needed to achieve 100 percent accuracy can grow exponentially. To solve this problem, the researchers used a third error-correction stage drawing on the recent work of other scientists.
By freely providing the blueprint to the research community, they hope to interest engineers in setting up real-world experiments.


The one thing everyone knows about quantum mechanics is its legendary weirdness, in which the basic tenets of the world it describes seem alien to the world we live in. Superposition, where things can be in two states simultaneously, a switch both on and off, a cat both dead and alive. Or entanglement, what Einstein called “spooky action-at-distance” in which objects are invisibly linked, even when separated by huge distances.
But weird or not, quantum theory is approaching a century old and has found many applications in daily life. As John von Neumann once said: “You don’t understand quantum mechanics, you just get used to it.” Much of electronics is based on quantum physics, and the application of quantum theory to computing could open up huge possibilities for the complex calculations and data processing we see today.
Imagine a computer processor able to harness super-position, to calculate the result of an arbitrarily large number of permutations of a complex problem simultaneously. Imagine how entanglement could be used to allow systems on different sides of the world to be linked and their efforts combined, despite their physical separation. Quantum computing has immense potential, making light work of some of the most difficult tasks, such as simulating the body’s response to drugs, predicting weather patterns, or analysing big datasets.
Such processing possibilities are needed. The first transistors could only just be held in the hand, while today they measure just 14 nm – 500 times smaller than a red blood cell. This relentless shrinking, predicted by Intel founder Gordon Moore as Moore’s law, has held true for 50 years, but cannot hold indefinitely. Silicon can only be shrunk so far, and if we are to continue benefiting from the performance gains we have become used to, we need a different approach.
Advances in semiconductor fabrication have made it possible to mass-produce quantum-scale semiconductors – electronic circuits that exhibit quantum effects such as super-position and entanglement.
The image, captured at the atomic scale, shows a cross-section through one potential candidate for the building blocks of a quantum computer, a semiconductor nano-ring. Electrons trapped in these rings exhibit the strange properties of quantum mechanics, and semiconductor fabrication processes are poised to integrate these elements required to build a quantum computer. While we may be able to construct a quantum computer using structures like these, there are still major challenges involved.
In a classical computer processor a huge number of transistors interact conditionally and predictably with one another. But quantum behaviour is highly fragile; for example, under quantum physics even measuring the state of the system such as checking whether the switch is on or off, actually changes what is being observed. Conducting an orchestra of quantum systems to produce useful output that couldn’t easily by handled by a classical computer is extremely difficult.
But there have been huge investments: the UK government announced £270m funding for quantum technologies in 2014 for example, and the likes of Google, NASA and Lockheed Martin are also working in the field. It’s difficult to predict the pace of progress, but a useful quantum computer could be ten years away.
The basic element of quantum computing is known as a qubit, the quantum equivalent to the bits used in traditional computers. To date, scientists have harnessed quantum systems to represent qubits in many different ways, ranging from defects in diamonds, to semiconductor nano-structures or tiny superconducting circuits. Each of these has is own advantages and disadvantages, but none yet has met all the requirements for a quantum computer, known as the DiVincenzo Criteria.
The most impressive progress has come from D-Wave Systems, a firm that has managed to pack hundreds of qubits on to a small chip similar in appearance to a traditional processor.
The benefits of harnessing quantum technologies aren’t limited to computing, however. Whether or not quantum computing will extend or augment digital computing, the same quantum effects can be harnessed for other means. The most mature example is quantum communications.
Quantum physics has been proposed as a means to prevent forgery of valuable objects, such as a banknote or diamond, as illustrated in the image below. Here, the unusual negative rules embedded within quantum physics prove useful; perfect copies of unknown states cannot be made and measurements change the systems they are measuring. These two limitations are combined in this quantum anti-counterfeiting scheme, making it impossible to copy the identity of the object they are stored in.
The concept of quantum money is, unfortunately, highly impractical, but the same idea has been successfully extended to communications. The idea is straightforward: the act of measuring quantum super-position states alters what you try to measure, so it’s possible to detect the presence of an eavesdropper making such measurements. With the correct protocol, such as BB84, it is possible to communicate privately, with that privacy guaranteed by fundamental laws of physics.
Quantum communication systems are commercially available today from firms such as Toshiba and ID Quantique. While the implementation is clunky and expensive now it will become more streamlined and miniaturised, just as transistors have miniaturised over the last 60 years.
Improvements to nanoscale fabrication techniques will greatly accelerate the development of quantum-based technologies. And while useful quantum computing still appears to be some way off, it’s future is very exciting indeed.


Scientists at the University of Darmstadt, in Germany, have trapped a pulse of light inside a crystal for a minute, and used it to store an image, raising the possibility of light-based computers that could work faster than today’s electronic processors and transistors.
The results could have practical significance in future computer systems that operate using light, and could pave the way for quantum computing and communications.
‘We are reaching the principal limits of conventional electronic data processing,’ said Professor Thomas Halfmann, who coordinates the EU-funded project Marie Curie Initial Training Network - Coherent Information Processing in Rare-Earth Ion Doped Solids (CIPRIS).
Light usually travels at a speed of just under 300 million metres per second, making it the fastest thing in the universe, and computer scientists and physicists believe that computers in the future need to be optical to achieve faster processing speeds.
Currently, optical technology is mainly confined to communication networks, where light carries information through optical fibres. However, at the ends of the fibres the light signals have to be converted to and from the electrical signals that computers use to process information.
In the future, it is hoped that optical quantum computers will be able to process information using light, and the first step towards this is being able to store optical data in quantum systems.
‘We need media to store light and this is what is called an optical or quantum memory,’ said Prof. Halfmann. ‘What we have done is demonstrate an optical memory in a solid-state quantum system that can store light for one minute.’
They did it by using a control laser to manipulate the speed of the light in the crystal, which contained a low concentration of ions – electrically charged atoms – of the element praseodymium. When the light source then came into contact with the crystal, it rapidly decelerated. The scientists then switched off the laser beam and the light came to a complete halt.
‘In simple terms you transfer energy from one oscillator, the light field, into the other oscillator, the atom, and there it stays and then you can retrieve it afterwards.’
Professor Thomas Halfmann, the coordinator of MC ITN - CIPRIS
Technically, the light wasn’t stopped, but it was converted into the atomic medium, Prof. Halfmann explained. ‘What happens is we convert the light pulse into something called an atomic oscillator.
‘In simple terms, you transfer energy from one oscillator, the light field, into the other oscillator, the atom, and there it stays and then you can retrieve it afterwards.’
Storing an image
The researchers imprinted an image consisting of three stripes onto the light pulse, demonstrating that they could store the image inside the crystal for a minute and then retrieve it, smashing the previous image storage record, which was less than ten microseconds.
The fact they stored an image is significant for developments in computing because, while a single light pulse contains one ‘bit’ of data, an image contains many.
‘These stripes are just one simple image you can store, but essentially you can store any image,’ Prof. Halfmann said.
Professor Halfmann in the laboratory. ©Katrin Binner/ TU Darmstadt
Usually light storage times are very short because ‘perturbing environments’ disrupt the oscillation. However, the team managed to achieve their record-breaking storage time by protecting the oscillator with magnetic fields and high-frequency pulses.
Using complex algorithms, they were able to optimise the laser beams, magnetic field and high-frequency pulses so that the oscillation lasted almost as long as theoretically possible in the crystal.
Prof. Halfmann likened the process of trapping the light to a person running through a crowd at a funfair with a briefcase full of papers. ‘When you run, you collide with people and if you collide often enough you lose your suitcase, your information, your papers.
‘So, what we do is we shield the information with these magnetic fields and we protect it somehow. It is like running through the funfair with bodyguards, big tough guys, around you. They protect you on your way through the crowd and nothing happens to you and your suitcase with your papers.’
The scientists have almost reached the theoretical storage limit of the crystal they used in this research, which is 100 seconds. But, they already have a different type of crystal set up in their laboratory and have started working with it.
Although there is some debate over the exact timeframe, the new crystal is theoretically capable of storing a light pulse for between a few hours to a week, and Prof. Halfmann believes that in two to three years they will again be very close to the limit of that crystal.
Quantum computers could revolutionise science by offering a new way of solving complex problems beyond the scope of standard transistor-based computers.
While normal computers are limited to ‘bits’, short for binary digits ( 0 or 1), quantum computers could be much more powerful because they could store information in qubits, short for quantum bits, using photons or atoms.
That’s because an atom can simultaneously have different energy states, or a photon of light may have multiple polarisations.
It means that a quantum computer would be able to solve many types of data encryption that are used today.
However, functioning quantum computers are still five or 10 years in the future, many researchers say, and it could take a couple more decades to reach the stage where quantum computers harness enough qubits to perform significant mathematical tasks.
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fires one photon at a time
Technology Research News
The weird nature of quantum physics makes
perfectly secure communications possible. The technology has existed in
the laboratory for several years -- all that remains is figuring out how
to make it practical.
Scientists at Toshiba Research and the University of Cambridge have taken
an important step in that direction by making an electronic device that
emits single photons on demand. The device could boost the transmission
rates of secret communications and would be smaller and easier to use
than similar light sources.
uses strings of individual photons, which are the indivisible particles
of light, to make the mathematical keys that scramble secret messages.
The keys are long, random numbers in the form of bits, the ones and zeros
of digital communications. Ordinary communications transmits bits as light
pulses, but because each light pulse contains many photons an eavesdropper
could siphon some of them off to record the series of pulses to get a
copy of the key without being detected.
However, when the keys' bits are encoded in the quantum states of individual
photons -- like how they are polarized -- eavesdroppers can't escape detection.
Because a photon cannot be split, an eavesdropper can't look at it without
stopping it from reaching the intended receiver. And an eavesdropper can't
cover his tracks by making copies of the photons he intercepts because
he cannot reliably recreate their quantum states, which means the sender
and receiver can compare notes to see that some of the photons have been
When a sender and receiver know they have an uncompromised key, the sender
can use it to encrypt messages that only the receiver can unscramble.
Making practical quantum cryptographic systems requires light sources
that produce one photon at a time. A candle flame emits about one hundred
thousand trillion photons per second, many at the same time.
Even the dimmest possible ordinary light source occasionally emits two
photons at once. "We can control and trigger the emission time of the
photons," said Andrew Shields, a group leader at Toshiba Research Europe
in Cambridge, England.
Single-photon light sources are not new, but previous devices have all
been triggered by lasers. "This is a cumbersome and expensive arrangement
that would be difficult to achieve outside the laboratory," said Shields.
"The new device is driven by a voltage so [it] is more robust, compact
and would be cheaper to manufacture."
The researchers' single-photon source, a special type of light emitting
diode (LED), contains a layer of quantum dots surrounded by layers of
semiconductor material. Each quantum dot, which is a speck of semiconductor
material about 20 nanometers in diameter, holds a single electron when
a voltage is applied to the device. When the negatively- charged electron
combines with a positively-charged hole in the quantum dot, it releases
the energy as a single photon. A nanometer is one millionth of a millimeter.
The diode is capped by a metal layer with a series of small openings that
block all but a single quantum dot per opening. By pulsing electrical
current through the device, the researchers cause the quantum dots to
emit a photon per pulse.
The device can theoretically emit a photon every half a nanosecond, said
Shields. A nanosecond is one billionth of a second. But in practice the
researchers' diode does not emit a photon with every pulse.
"The efficiency has not been optimized in this prototype, so [it] is quite
low," said Shields. "If we use a cavity structure to direct more of the
light out of the device in a certain direction, we can expect efficiencies
exceeding 10 percent."
Ten percent efficiency could be good enough for practical devices. A potentially
bigger hurdle is the cold temperatures needed to run the diode. The researchers'
prototype operates at five degrees Kelvin, or -268 degrees Celsius.
"We have already seen efficient emission from quantum dots at temperatures
exceeding [-73 degrees Celsius], for which cryogen-free thermal-electric
cooling can be used," said Shields. "We hope to be able to push this further
to room temperature."
A single-photon source that is triggered by an electrical current would
be much more practical than an optically triggered single-photon source,
said Gerard Milburn, a physics professor at the University of Queensland
in Australia. "The control circuits could be integrated into the device
producing the photons and processing their detection."
Without single-photon sources, researchers have to use privacy amplification
techniques to ensure that transmitted bits remain secret, which results
in less efficient transmission rates, said Richard Hughes, a physicist
at Los Alamos National Laboratory.
This new light source technology could lead to higher secret bit rates
if it could be made into a practical device, he said. Making an electrically-driven
device is a big step in that direction, "but it would also be important
for a practical device to operate at a temperature that would not require
the user to deal with cryogens."
The researchers next steps are to increase the efficiency and raise the
operating temperature of the single-photon diode, said Shields. "There
are technological challenges to overcome, but we think we know the solutions.
We think we can make a useful device within three years," he said.
Shields' research colleagues were Zhiliang Yuan, Beata E. Kardynal and
R. Mark Stevenson of Toshiba Research, Charlene J. Lobo, Ken Cooper and
David A. Ritchie of the University of Cambridge, and Neil S. Beattie and
Michael Pepper of both institutions. They published the research in the
December 13, 2001 online issue of the journal Science. The research was
funded by Toshiba Corporation in the Engineering and Physical Sciences
Research Council of the UK.
Timeline: <3 years
Funding: Corporate; Government
TRN Categories: Optical Computing, Optoelectronics and
Photonics; Quantum Computing; Semiconductors
Story Type: News
Related Elements: Technical paper, "Electrically captured
in Single Photon Source," Science, online December 13, 2001
LED fires one photon
at a time
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on unlocked Web sites
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Researchers at Washington State University have used a super-cold cloud of atoms that behaves like a single atom to see a phenomenon predicted 60 years ago and witnessed only once since.
The phenomenon takes place in the seemingly otherworldly realm of quantum physics and opens a new experimental path to potentially powerful quantum computing.
Working out of a lab in WSU's Webster Hall, physicist Peter Engels and his colleagues cooled about one million atoms of rubidium to 100 billionths of a degree above absolute zero. There was no colder place in the universe, said Engels, unless someone was doing a similar experiment elsewhere on Earth or on another planet.
At that point, the cluster of atoms formed a Bose-Einstein condensate - a rare physical state predicted by Albert Einstein and Indian theorist Satyendra Nath Bose - after undergoing a phase change similar to a gas becoming a liquid or a liquid becoming a solid. Once the atoms acted in unison, they could be induced to exhibit coherent "superradiant" behavior predicted by Princeton University physicist Robert Dicke in 1954.
"This large group of atoms does not behave like a bunch of balls in a bucket," said Engels. "It behaves as one big super-atom. Therefore it magnifies the effects of quantum mechanics."
Engels' findings appear in the journal Nature Communications. Co-author and collaborator Chuanwei Zhang, a former WSU physicist now at the University of Texas at Dallas, led the theoretical aspects of the work.
Funders include the National Science Foundation, the Army Research Office and the Defense Advanced Research Projects Agency, the cutting-edge research agency known as DARPA.
Researchers using these super-cold dilute gases have created the superradiant state in only one other situation, said Engels, using a far more complicated experiment involving coupling to photon fields. Because the coupling of atoms and photons is usually very weak, their behavior was extremely hard to observe, he said.
"What our colleague Chuanwei Zhang realized is, if you replaced the light with the motion of the particles, you got exactly the same physics," said Engels. Moreover, it's easier to observe. So while their cloud of atoms measures less than half a millimeter across, it is large enough to be photographed and measured. This gives experimenters a key tool for testing assumptions and changes in the atomic realm of quantum physics.
"We have found an implementation of the system that allows us to go in the lab and actually test the predictions of the Dicke model, and some extensions of it as well, in a system that is not nearly as complicated as people always thought it has to be for the Dicke physics," Engels said.
Ordinary physical properties change so dramatically in quantum mechanics that it can seem like a drawing by M.C. Escher. Photons can be both waves and particles. A particle can go through two spaces at the same time and, paradoxically, interfere with itself. Electrons can be oriented up or down at the same time.
This concurrent duality can be exploited by quantum computing. So where a conventional computer uses 1s and 0s to make calculations, the fundamental units of a quantum computer could be 1s and 0s at the same time. As Wired magazine recently noted, "It's a mind-bending, late-night-in-the-dorm-room concept that lets a quantum computer calculate at ridiculously fast speeds."
Peter Engels | Eurek Alert!
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Permanent magnets are very important for technologies of the future like electromobility and renewable energy, and rare earth elements (REE) are necessary for their manufacture. The Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany, has now succeeded in identifying promising approaches and materials for new permanent magnets through use of an in-house simulation process based on high-throughput screening (HTS). The team was able to improve magnetic properties this way and at the same time replaced REE with elements that are less expensive and readily available. The results were published in the online technical journal “Scientific Reports”.
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In the Beyond EUV project, the Fraunhofer Institutes for Laser Technology ILT in Aachen and for Applied Optics and Precision Engineering IOF in Jena are developing key technologies for the manufacture of a new generation of microchips using EUV radiation at a wavelength of 6.7 nm. The resulting structures are barely thicker than single atoms, and they make it possible to produce extremely integrated circuits for such items as wearables or mind-controlled prosthetic limbs.
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The trend-forward world of display technology relies on innovative materials and novel approaches to steadily advance the visual experience, for example through higher pixel densities, better contrast, larger formats or user-friendler design. Fraunhofer ISC’s newly developed materials for optics and electronics now broaden the application potential of next generation displays. Learn about lower cost-effective wet-chemical printing procedures and the new materials at the Fraunhofer ISC booth # 1021 in North Hall D during the SID International Symposium on Information Display held from 22 to 27 May 2016 at San Francisco’s Moscone Center.
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20 Most Impressive Science Fair Projects of All Time
While science fair projects still typically consist of papier mache volcanoes, LEGO robots, and crystals grown in a jar, many students these days are going above and beyond the staples, taking on projects that would even be awe-inspiring as a college thesis. From exploring the effectiveness of cancer treatments to revolutionizing the disposal of plastics, these students prove you don't have to be an adult to have amazing, world-changing ideas about science.
1. Nuclear Fusion Reactor — Thiago Olsen
With a budget of only $3,500, Michigan high school student Thiago Olsen built a nuclear fusion reactor in his garage when he was only 15 years old. How did he do it? He studied physics textbooks, used vacuum pump manuals, and surfed the Web for the best deals on parts. While his device is not self-sustaining and produces fusion only on a small scale, it's a pretty impressive feat for any teenager.
2. Diesel Hybrid Car — West Philadelphia High School
Working as a team at West Philadelphia High School, students constructed a diesel-hybrid race car that can go from zero to 60 in just four seconds. If that speed wasn't already impressive enough, the vehicle also gets more than 60 miles to the gallon. The students constructed it for entry into the Automotive X contest, with a grand prize of $10 million — the only high schoolers in the nation to do so. They are reworking their design to improve their chances of winning, and hope to get the car up to 100 mpg.
3. Chemical-Sniffing LEGO Robot — Anna Simpson
Many a science fair project involves LEGOs, but few on the level that Anna Simpson's does. Her robot, built of the plastic blocks, is capable of sniffing out toxic chemicals and other hazards, keeping humans at a safe distance. Simpson's work won her the California State Science Fair and could have a number of industrial and public safety applications if adapted.
4. Reducing CO2 Emissions — Jun Bing and Alec Wang
Using a process known as acid base neutralization, Bing and Wang developed a device capable of sequestering carbon dioxide gas released from cars (and other sources) that burn fossil fuel. Not only does it remove the harmful substance from the air, but also collects in a way so it can be stored, used or sold.
5. Plastic-Eating Microbe — Daniel Burd
Plastic that is simply dumped into landfills can take centuries to decompose, if it ever really does, but this young thinker came up with a better way. Burd beat out leading scientists to discovering a microbe that eats plastic, increasing the rate of decomposition by more than 40 percent. This project won him the Canada-Wide Science Fair and garnered a fair amount of international media attention as well.
6. Space Exploration Balloon — IES La Bisbal School
The students at this Spanish school produced a science fair project that was out of this world — literally. A team of four students sent a camera-operated weather balloon into the stratosphere, snagging atmospheric readings and stunning photographs more than 20 miles above Earth's surface.
7. Cancer And Chicken Marinades — Lauren Hodge
At just 14 years old, Lauren Hodge is getting a jumpstart on a science career with this amazing project, which won her an award at the international Google Science Fair competition. So what did she find? Some chicken marinades block carcinogenic compounds from forming when chicken is grilled — a process known to raise the level of carcinogens in meat. Among the marinades she tested, lemon juice was the most successful, so consider these stellar findings the next time you're hosting a backyard BBQ.
8. Image-Based Search Engine — David Liu
While most search engines work at dissecting the Web's textual information, David Liu's pet project is all about creating one that looks at images instead. While he is still working to perfect his software, Liu's search engine is already being used in the real world, analyzing satellite images and making relevant Web searches much more effective. An impressive feat for a 17-year-old.
9. Problems With Ovarian Cancer Treatment — Shree Bose
Taking top prize at the Google Science Fair, Bose will get to spend several weeks studying marine life in the Galapagos Islands. The work that netted her this prize is awe-inspiring, especially coming from a teenager. Bose uncovered a number of problems with popular ovarian cancer treatments and drugs, producing a report that would be more at home in a medical journal than a high school classroom. Hopefully, this will influence some changes in how treatment is doled out to suffering patients.
10. Computer Speed Enhancing Software — Kevin Ellis
Slow computers are the bane of every office worker's existence, but with the work of Kevin Ellis, an unresponsive machine may be a thing of the past. Rather than upgrading computers with more memory, Ellis has developed software that analyzes how programs are running and spreads out their needs over all the CPUs to make everything more quickly. His amazing software netted him $50,000 and the rest of the world a way to speed up computers that may have otherwise been tossed out.
11. Quantum Computing For Difficult Computational Problems — Yale Fan
Despite his name, this young genius chose Harvard over Yale to continue working on his education. Part of what got him there, undoubtedly, was this impressive bit of science. Yale's research project, titled "Adiabatic Quantum Algorithms for Boolean Satisfiability" analyzed the applications of quantum computing for solving some of the most complex and difficult computational problems. Most adults don't have half an idea what that even means, so it's all the more impressive that this teen was already studying it in high school.
12. Photodynamic Cancer Therapy — Amy Chyao
The definitive cure for cancer is still undoubtedly a long way off, but young researchers like Amy Chyao are certainly helping in the fight with innovative new ideas. Amy's science project used photodynamic therapy to target and kill cancer cells. The project was so promising, it garnered her the Intel International Science and Engineering Fair award in 2010.
13. Antarctic Submersible — Ryan Garner and Amanda Wilson
These two teens have come up with an amazing way to do research on climate change. With a budget of $5,000, the pair built an underwater rover designed to take on the challenges of some of the harshest conditions in the world — like those at the Antarctic Circle. Equipped with a camera, the device can explore and take measurements, and is currently being used by the University of California-Santa Barbara to study marine life.
14. Nuclear Weapon Detector — Taylor Wilson
16-year-old Taylor Wilson began his nuclear detection project at the age of only 11. Supported by his parents and a grant from Homeland Security, he eventually created a device that can reliably detect nuclear weapons and explosive materials as vehicles pass through his drive-through sensor.
15. Teaching Robots To Speak English — Luke Taylor
South African Luke Taylor submitted this amazing project to Google's Science Fair, which lets humans communicate more easily with robots. His software translates the English language into code that the robot can then understand and execute — allowing just about anyone, anywhere to program one to perform a variety of functions. Even more impressive? Taylor is just 13 years old.
16. Better Password Technology — Jacob Buckman
How many of your online passwords are truly secure? If you're like most people, probably not many. This young man may have come up with a solution, monitoring the biometrics of how people type to create a more secure way of gaining online account access. He discovered that passwords using the length of time between keystrokes and the length of time keys were held down could be just as accurate and potentially more secure than traditional passwords.
17. Asthma And Air Quality — Naomi Shah
Taking home top prize in her age group at the Google Science Fair, Shah's work takes a critical look at the air quality in the world today — and the impact it can have on those suffering from breathing disorders like asthma. She created a mathematical model that helps quantify the effects of air quality on symptoms. And had a few harsh words about the U.S. Clean Air Act as well, based on her findings.
18. Mind-controlled Prosthetic Limbs — Anand Srinivasan
It's hard to believe that this awe-inspiring science project came from the mind of a 14-year-old. Hooking his brain up to an EEG scanner, Srinivasan worked to test out a new method of improving mind-controlled prosthetic limbs. He found that data from the EEG could help with data classification and signal processing when using them, providing a better and more efficient user experience.
19. Managing The Power Of Household Devices — Ankush Gupta
You likely have a lot of vampires in your home, and not the sexy Hollywood kind either. These are energy vampires, and they're sucking up and wasting energy that you're paying for. Gupta has come up with a solution with this amazing science project using demotic technology. By monitoring energy use around the home, Gupta's system allows users to manage the power states of computers and other devices around the home to reduce energy usage and save money.
20. Spacecraft Navigation Software — Erika DeBenedictis
This bright, young rising star in the scientific community came up with some ingenious software for helping spacecraft move faster and use less fuel while navigating many obstacles in the vacuum of space. Her amazing software won a substantia


Like the one in your car, Johannes Roßnagel's engine is a four-stroke. In four steps it compresses and heats, then expands and cools. And as with any other engine, this cycle is repeated over and over again—transforming the changing temperature into mechanical energy.
But Roßnagel's engine is no V-8. And it doesn't use internal combustion. Roßnagel, an experimental physicist at the University of Mainz in Germany, has conceived of and is in the process of building the world's tiniest engine, less than a micrometer in length. It is a machine so small it runs on a single atom. And in a recent paper in the journal Physical Review Letters, its inventors argue that, because of an interesting anomaly of quantum physics, this is also far and away the most efficient engine.
The nano engine works like this: First, using tiny electrodes, the physicists trap a single atom in a cone of electromagnetic energy. "We're using a calcium-40 ion," Roßnagel says, "but in principle the engine could be built with just about any ion at all." This electromagnetic cone is essentially the engine's housing, and squeezes tightly over the atom. The physicists then focus two lasers on each end of the cone: one at the pointy end, which heats the atom, and another at the base of the cone, which uses a process called Doppler cooling to cool the atom back down.
Because this heating and cooling slightly changes the size of the atom (more exactly, it alters the fuzzy smear of probability of where the atom exists), and the cone fits the atom so snuggly, the temperature change forces the atom to race back and forth along the length of the cone as the atom expands and contracts. For maximum efficiency, the physicists set the lasers to heat and cool at the same resonance at which the atom naturally vibrates from side to side.
The result is that, like sound waves that build upon one other, the atom's oscillation between the two ends of the cone "gets accumulated, and becomes stronger and stronger," which can be harnessed, Roßnagel says. "If you imagine that you put a second ion by the cooler side, it could absorb the mechanical energy of our engine, much like a flywheel [in a car engine]."
And the nano engine has one additional feature, one that, Roßnagel argues, increases the efficiency of the machine so much that it actually surpasses the Carnot Limit—the maximum efficiency any engine can have according to the laws of thermodynamics.
As the racing atom reaches the hot end to the cone, the researchers slightly contract and expand the sides of the cone a single time. Done at the right frequency, this action puts the moving atom into a quantum mechanical condition called a squeezed state. This means that now, as the atom continues race to the cold end of the cone, it's also slightly pulsating.
Although forcing the atom into a squeezed state doesn't actually transfer any energy, it does mean that the pulsating atom is (because of a quantum mechanical quirk) on average slightly bigger when it hits the cold end of the cone. And while the cooling phase knocks the atom out of this squeezed state, the momentary extra size gives the entire engine a boost. "You can think of it sort of like a supercharger," says Jacob Taylor, a quantum physics researcher at the University of Maryland, who was not involved in the experiment. According to Roßnagel, if you calculate the energy efficiency of this supercharged system, it's four times as efficient as it would be without the squeezing—surpassing the Carnot Limit by a large margin. This would make it the most efficient engine ever built.
However, any claims that an engine can break the laws of thermodynamics deserves extra scrutiny and skepticism. According to Taylor, this ultrahigh efficiency is only a matter of perspective. "There's no free lunch here," he says. Despite the fact that the squeezing process doesn't transfer any energy to the atom's side-to-side movement, "you still have to consider the energy that goes into the squeezing process. You're essentially taking energy from the squeezing process to turbo-boost the engine." And calculating in that squeezing energy, the engine is safely below the Carnot Limit.
Hartmut Häffner, a theoretical physicist at the University of California, Berkeley, who was not involved in the experiment, agrees. "I wouldn't accept this efficiency is just from 'the weirdness of quantum mechanics,'" says Häffner, but he adds that the proposed nano engine itself "is very interesting and very well-described. It's trying to push the boundaries of what we know about thermodynamics into a new regime."
Roßnagels argues that because the squeezing process doesn't actually transfer any energy to the atom's side-to-side movement along the cone, including it in the efficiency calculation for his nano engine is a bit arbitrary. It's like looking at the energy efficiency of a gasoline engine and incorporating in the millions of years of energy it took to create the fossil fuels, he says, or the energy it took to pump the oil out of the ground. He is generally in agreement with Taylor, though, that it all depends on how you look at it. "In general it's kind of a semantic problem," Roßnagel says. "It's where you put your camera and decide what is part of the system and what isn't part of the system."
The sheer amount of laboratory space and equipment these nano engines require means that we won't see them outside a lab anytime soon. (Or perhaps ever. Sorry, nanobots!) But Taylor says the insight we'll gain from this type of experiment can be incredibly helpful in other realms— chiefly, quantum computing. The pursuit of building computers that manipulate the funky physics of quantum mechanics to process information has already captured some of brightest minds in theoretical physics. "And in quantum computation you really need the ability to efficiently move heat around," Taylor says, "and in so far as we can better understand these heat engines, it may improve our ability in developing quantum computers down the road."


Are we alone?
1. We have strong evidence that that our solar system is not the only one; we know there are many other Suns with planets orbiting them.
Improved telescopes and detectors have led to the detection of dozens of new planetary systems within the past decade, including several systems containing multiple planets.
One giant leap for bug-kind
2. Some organisms can survive in space without any kind of protective enclosure.
In a European Space Agency experiment conducted in 2005, two species of lichen were carried aboard a Russian Soyuz rocket and exposed to the space environment for nearly 15 days. They were then resealed in a capsule and returned to Earth, where they were found in exactly the same shape as before the flight. The lichen survived exposure to the vacuum of space as well as the glaring ultraviolet radiation of the Sun.
Hot real estate
3. Organisms have been found living happily in scalding water with temperatures as high as 235 degrees F.
More than 50 heat-loving microorganisms, or hyperthermophiles, have been found thriving at very high temperatures in such locations as hot springs in WyomingÕs Yellowstone National Park and on the walls of deep-sea hydrothermal vents. Some of these species multiply best at 221 degrees F, and can reproduce at up to 235 degrees F.
Has E.T. already phoned home?
4. We now have evidence that some form of life exists beyond Earth, at least in primitive form.
While many scientists speculate that extraterrestrial life exists, so far there is no conclusive evidence to prove it. Future missions to Mars, the Jovian moon Europa and future space telescopes such as the Terrestrial Planet Finder will search for definitive answers to this ageless question.
To infinity, and beyond!
5. We currently have the technology necessary to send astronauts to another star system within a reasonable timespan. The only problem is that such a mission would be overwhelmingly expensive.
Even the the unmanned Voyager spacecraft, which left our solar system years ago at a breathtaking 37,000 miles per hour, would take 76,000 years to reach the nearest star. Because the distances involved are so vast, interstellar travel to another star within a practical timescale would require, among other things, the ability the move a vehicle at or near the speed of light. This is beyond the reach of today's spacecraft -- regardless of funding.
Fellowship of the rings
6. All of the gas giant planets in our solar system (Jupiter, Saturn, Uranus and Neptune) have rings.
Saturn's rings are the most pronounced and visible, but they aren't the only ones.
May the force be with you
7. In the "Star Wars" films, the Imperial TIE Fighters are propelled by ion engines (TIE stands for Twin Ion Engine). While these spacecraft are fictional, real ion engines power some of todayÕs spacecraft.
Ion propulsion has long been a staple of science fiction novels, but in recent years it has been successfully tested on a number of unmanned spacecraft, most notably NASAÕs Deep Space 1. Launched in 1998, Deep Space 1 rendezvoused with a distant asteroid and then with a comet, proving that ion propulsion could be used for interplanetary travel.
A question of gravity
8. There is no gravity in deep space.
If this were true, the moon would float away from the Earth, and our entire solar system would drift apart. While itÕs true that gravity gets weaker with distance, it can never be escaped completely, no matter how far you travel in space. Astronauts appear to experience "zero-gravity" because they are in continuous free-fall around the Earth.
9. The basic premise of teleportation -- made famous in TVÕs "Star Trek" -- is theoretically sound. In fact, scientists have already ÒteleportedÓ the quantum state of individual atoms from one location to another.
As early as the late 1990s, scientists proved they could teleport data using photons, but the photons were absorbed by whatever surface they struck. More recently, physicists at the University of Innsbruck in Austria and at the National Institute of Standards and Technology in Boulder, Colorado, for the first time teleported individual atoms using the principle of quantum entanglement.
Experts say this technology eventually could enable the invention of superfast "quantum computers." But the bad news, at least for sci-fi fans, is that experts donÕt foresee being able to teleport people in this manner.
Good day, Suns-shine
10. Tatooine, Luke Skywalker's home planet in the "Star Wars" films, has two Suns -- what astronomers would call a binary star system. Scientists have discovered recently that planets really can form within such systems.
Double-stars, or binary systems, are common in our Milky Way galaxy. Among the more than 100 new planets discovered in recent years, some have been found in binary systems, including16 Cygni B and 55 Cancri A. (But so far, no one has found a habitable planet like Luke Skywalker's Tatooine.)


If quantum computers are ever going to perform all those expected feats of code-breaking and number crunching, then their component qubits---tiny ephemeral quantum cells held in a superposition of internal states---will have to be protected from intervention by the outside world. In other words, decoherence, the loss of the qubits' quantum integrity, has to be postponed. Now theoretical physicists at the Joint Quantum Institute (JQI) and the University of Maryland have done an important step forward to understand qubits in a real-world setup. In a new study they show, for the first time, that qubits can successfully exist in a so called topological superconductor material even in the presence of impurities in the material and strong interactions among participating electrons. To see how qubits can enter into their special coherence-protection program, courtesy of "Majorana particles," an exotic form of excitation, some groundwork has to be laid.
Most designs for qubits involve materials where quantum effects are important. In one such material, superconductors (SC), electrons pair up and can then enter into a large ensemble, a supercurrent, which flows through the material without suffering energy loss. Another material is a sandwich of semiconductors which support the quantum Hall effect (QHE). Here, very low temperatures and a powerful external magnetic field force electrons in a thin boundary layer to execute tiny cyclone motions (not exactly, but ok--also isn't a cyclone a storm?). At the edge of these layers, the electrons, unable to trace out a complete circular path, will creep along the edge, where they constitute a net electrical current.
One of the most interesting and useful facts about these electrons at the edge is that they move in one direction. They cannot scatter backwards no matter how many impurities (which in ordinary conductors can lead to energy dissipation) may be in the material. If, furthermore, the electrons can be oriented according to their spin---their intrinsic angular momentum---then we get what is called the quantum spin Hall effect (QSH). In this case all electrons with spin up will circulate around the material (at the edge) in one direction, while electrons with spin down will circulate around in the opposite direction.
The QHE state is depicted in figure 1.
In some materials the underlying magnetism of the nuclei in the atoms making of the material is so strong than no external magnet is needed to create the Hall effects. Mercury-cadmium-telluride compounds are examples of materials called topological insulators. Insulators (not sure how this sentence was supposed to start, but grammatically is currently confusing) because even as electrons move around the edge of the material with very little loss of energy, the interior of these 3-dimensional structures is an insulator; no current flows. The "topological" is a bit harder to explain. Partly the flow of current on the outside bespeaks of geometry: the electrons flow only at the edge and are unable (owing to quantum interactions) from scattering backwards if they meet an impediment.
But topology in this case has more to do with the way in which the motion of the electrons in these materials are described in terms of "dispersion relations." Just as waves of white light will be dispersed into a spectrum of colors when the waves strike the oblique side of a prism, so electron waves (electrons considered as quantum waves) will be "dispersed," in the sense that electrons with the same energy might have different momenta, depending on how the electrons move through the material in question.
The idea of electron dispersal is often depicted in the form of an energy-level diagram. In insulators (the left panel of Figure 2) electrons remain in a valence band; they don't have enough energy to visit the conduction band of energies; hence the electrons do not move; the material is an insulator against electricity. In a conductor (middle part) the conduction and valence bands overlap. In the QHE (right panel) electrons in the interior of the material also do not move along; the bulk of the material is an insulator. But for electrons at the edge there is a chance for movement into the conduction band.
Now for the topology: just as a coffee cup is equivalent to a donut topologically---either can be transformed into the other by stretching but not by any tearing---so here the valence band can be transformed into a conduction band (at least for edge states) no matter what impurities might be present in the underlying material. In other words, the "topological" nature of the material offers some protection for the flow of electrons against the otherwise-dissipating effects of impurities.
The marvelous properties of superconductors and topological materials can be combined. If a one-dimensional topological specimen---a nanowire made from indium and arsenic---is draped across a superconductor (niobium, say) then the superconductivity can extend into the wire (proximity effect). And in this conjunction of materials, still another hotly-pursued effect can come into play.
One last concept is needed here---Majorana particles---named for the Italian physicist Ettore Majorana, who predicted in 1937 the existence of a class of particle that would serve as its own antiparticle. Probably this object would not exist usefully in the form of a single real particle but would, rather, appear in a material as a quasiparticle, an ensemble excitation of many electrons.
Some scientists believe that qubits made from Majorana pulses excited in topological materials (and benefitting from the same sort of topological protection that benefits, say, electrons in QHE materials) would be much more immune from decoherence than other qubits based on conventional particles. Specifically Sankar Das Sarma and his colleagues at the University of Maryland (JQI and the Condensed Matter Theory Center) predicted that Majorana particles would appear in topological quantum nanowires. In fact part of the Majorana excitation would appear at both ends of the wire. These predictions were borne out. It is precisely the separation of these two parts (each of which constitutes a sort of "half electron") that confers some of the anticipated coherence-protection: a qubit made of that Majorana excitation would not be disrupted by merely a local irregularity in the wire.
A recent experiment in Holland provides preliminary evidence for exactly this occurrence (***).
ROBUST QUBITS AMID DISORDER
One of the authors of the new study, Alejandro Lobos, said that the earlier Maryland prediction, useful as it was, was still somewhat idealistic in that it didn't fully grapple with the presence of impurities, a fact of life which all engineers of actual computers must confront. This is what the new paper, which appears in the journal Physical Review Letters, addresses.
The problem of impurities or defects (which flowing electrons encounter as a form of disorder) is especially important for components which are two or even one dimensional in nature. The same is true for the repulsive force among electrons. "In 3-dimensional materials," said Lobos, "electrons (and their screening clouds of surrounding holes) can avoid each other thanks to the availability of space. They can just go around each other. In 1-D materials, this is not possible, since electrons cannot pass each other. In 1D, if one electron wants to move, it has to move all the other electrons! This ensures that excitations in a 1D metal are necessarily collective, as opposed to the single-particle excitations existing in a 3D metal.
So, in summary, the new Maryland work shows that disorder and electron interactions, two things that normally work to disrupt superconductivity, can be overcome with careful engineering of the material.
"A number of important theoretical studies before ours have focused on the destabilizing effects of either disorder or interaction on topological superconductors," said Lobos. "These studies showed the extent to which a topological superconductor could survive under these effects separately. But to make contact with real materials, disorder and interactions have to be considered on equal footing and simultaneously, a particular requirement imposed by the one-dimensional geometry of the system. It was then an important question to determine if it was possible to stabilize a topological superconductor under their simultaneous presence. The good news is that the answer is yes: despite their detrimental effect, there is still a sizable range of parameters where topological superconductors hosting Majorana excitations can exist. That's the main result of our study, which will be useful to understand and characterize topological superconductors in more realistic situations."
(*) The Joint Quantum Institute is operated jointly by the National Institute of Standards and Technology in Gaithersburg, MD and the University of Maryland in College Park.
(**) "Interplay of disorder and interaction in Majorana quantum wires," Alejandro M. Lobos, Roman M. Lutchyn, and S. Das Sarma, Physical Review Letters, 5 October 2012, http://prl.
(***) Link to earlier Majorana JQI press release and several pertinent research papers: http://www.
Alejandro M. Lobos, (301)405-0603, firstname.lastname@example.org


Quantum Computers Are a Quantum Leap Closer
Source Newsroom: Purdue University
Newswise — A new breed of faster, more powerful computers based on quantum mechanics may be a step closer to reality, report scientists from Purdue and Duke universities.
By linking a pair of tiny "puddles" of a few dozen electrons sandwiched inside a semiconductor, researchers have enabled these two so-called "quantum dots" to become parts of a transistor - the vital switching component in computer chips. Future computers that use quantum dots to store and process digital information might outperform conventional computer circuits because of both the new transistors' smaller size and their potential to solve problems that would take centuries on today's machines.
"This is a very promising candidate for quantum computation," said Albert M. Chang, who is an adjunct professor of physics in Purdue's School of Science. "We believe this research will allow large numbers of quantum-dot switches to work together as a group, which will be necessary if they are ever to function as a computer's brain, or memory.
"For the market, quantum computers mean better encryption methods and heightened data security. For science, our research may help address the longstanding mystery of the relationship between the classical physics of the world we see every day, and the peculiar world of quantum physics that governs the tiny particles inside atoms."
The research will appear in the current (April 30) issue of Physical Review Letters. The lead author is Jeng-Chung Chen, who received his doctorate at Purdue and is now at the University of Tokyo. Co-authors are Chang, who in 2003 relocated from Purdue to Duke University, where he is a professor of physics, and Michael. R. Melloch, a professor in Purdue's School of Electrical and Computer Engineering.
As computer circuits grow ever smaller, manufacturers draw nearer to the time when their chips' tiny on-off switches - representing the 1's and 0's of binary information, or bits - can be made comparable in size to a single molecule. At smaller scales, the laws of classical physics will no longer apply to the switches, but will be replaced by the laws of the subatomic world. These laws, described by quantum physics, can appear strange to the uninitiated.
"An electron, for example, can behave like a particle or a wave at times, and it has the odd ability to seemingly be in two different states at once," Chang said. "Physicists need a different set of words and concepts to describe the behavior of objects that can do such counterintuitive things. One concept we use is the 'spin' of an electron, which we loosely imagine as being similar to the way the Earth spins each day on its axis. But it also describes a sort of ordering electrons must obey in one another's presence: When two electrons occupy the same space, they must pair with opposite spins, one electron with 'up' spin, the other 'down.'"
Spin is one property that physicists seek to harness for memory storage. After collecting 40 to 60 paired electrons in a puddle within a semiconductor wafer of gallium arsenide and aluminum gallium arsenide, the team then added a single additional unpaired electron to the puddle. This extra electron imparted a net spin of up or down to the entire puddle, which they call a quantum dot. The team also built a second quantum dot nearby with the same net spin.
"When isolated from one another, the two net spins would not seek to pair with each other," Chang said. "But we have a special method of 'tuning' the two-dot system so that, despite the similar spins, the two unpaired electrons became 'entangled' - they begin to interact with one another."
The team used eight tiny converging wires, or "gates," to deposit the electrons in the dots one by one and then electronically fine-tune the dots' properties so they would become entangled. With these gates, the team was able to slowly tune the interacting dots so they are able to exist in a mixed, down-up and up-down configuration simultaneously. In each dot, an up or down configuration would represent a 1 or 0 in a quantum bit, or "qubit," for possible use in memory chips.
"Entanglement is a key property that would help give a quantum computer its power," Chang said. "Because each system exists in this mixed, down-up configuration, it may allow us to create switches that are both on and off at the same time. That's something current computer switches can't do."
Large groups of qubits could be used to solve problems that have myriad potential solutions that must be winnowed down quickly, such as factoring the very large numbers used in data encryption.
"A desktop computer performs single operations one after another in series," Chang said. "It's fast, but if you could do all those operations together, in parallel rather than in series, it can be exponentially faster. In the encryption world, solving some problems could take centuries with a conventional computer."
But for a quantum computer, whose bits can be in two quantum states at once - both on and off at the same time - many solutions could, in theory, be explored simultaneously, allowing for a solution in hours rather than lifetimes.
"These computers would have massive parallelism built right in, allowing for the solution of many tough problems," Chang said. "But for us physicists, the possibilities of quantum computers extend beyond any single application. There also exists the potential to explore why there seem to be two kinds of reality in the universe - one of which, in everyday language, is said to stop when you cross the border 'into the interior of the atom.'"
Because a quantum computer would require all its qubits to behave according to quantum rules, its processor could itself serve as a laboratory for exploring the quantum world.
"Such a computer would have to exhibit 'quantum coherence,' meaning its innards would be a large-scale system with quantum properties rather than classical ones," Chang said. "When quantum systems interact with the classical world, they tend to lose their coherence and decay into classical behavior, but the quantum-dot system we have built exhibits naturally long-lasting coherence. As an entire large-scale system that can behave like a wave or a particle, it may provide windows into the nature of the universe we cannot otherwise easily explore."
The system would not have to be large; each dot has a width of only about 200 nanometers, or billionths of a meter. About 5,000 of them placed end to end would stretch across the diameter of a grain of sand. But Chang said that his group's system had another, greater advantage even than its minuscule size.
"Qubits have been created before using other methods," he said. "But ours have a potential advantage. It seems possible to scale them up into large systems that can work together because we can control their behavior more effectively. Many systems are limited to a handful of qubits at most, far too few to be useful in real-world computers."
For now, though, the team's qubit works too slowly to be used as the basis of a marketable device. Chang said the team would next concentrate on improving the speed at which they can manipulate the spin of the electrons.
"Essentially, what we've done is just a physics experiment, no more," he said. "In the future, we'll need to manipulate the spin at very fast rates. But for the moment, we have, for the first time, demonstrated the entanglement of two quantum dots and shown that we can control its properties with great precision. It offers hope that we can reach that future within a decade or so."
This research was funded in part by the National Science Foundation.
STORY AND PHOTO CAN BE FOUND AT:
As part of an effort to make superpowerful quantum computers, Purdue University researchers have created "quantum dots" in a semiconducting material known as gallium arsenide. The quantum dots (the two small circular areas shown adjacent to one other in the center of the image) are puddles of about 40-60 electrons. Together the dots can form part of transistors in which the electrons' spin, a quantum mechanical property, could be harnessed to make logic gates for next-generation computer chips. Each dot measures only about 180 nanometers (billionths of a meter) in diameter - about 5,000 of them could stretch across the width of a grain of sand. (Illustration by Albert Chang, Duke University Department of Physics)
A publication-quality illustration is available at http://ftp.purdue.edu/pub/uns/+2004/chang-parallel.jpg
Transition Between Quantum States in a Parallel-Coupled Double-Quantum-Dot
J.C. Chen, A.M. Chang, and M.R. Melloch* - Department of Physics, Purdue University; *Electrical and Computer Engineering
Strong electron and spin correlations in a double-quantum-dot (DQD) can give rise to different quantum states. We observe a continuous transition from a Kondo state exhibiting a single-peak Kondo resonance to another exhibiting a double peak by increasing the inter-dot-coupling (t) in a parallel-coupled DQD. The transition into the double-peak state provides evidence for spin entanglement between the excess-electron on each dot. Toward the transition, the peak splitting merges and becomes substantially smaller than t because of strong Coulomb effects. Our device tunability bodes well for future quantum computation applications.


Spooky Atomic Clocks
Spooky Atomic Clocks
NASA-supported researchers hope to improve
high-precision clocks by entangling their atoms.
January 23, 2004: Einstein called it "spooky action at a distance." Now NASA-funded researchers are using an astonishing property of quantum mechanics called "entanglement" to improve atomic clocks--humanity's most precise way to measure time. Entangled clocks could be as much as 1000 times more stable than their non-entangled counterparts.
This improvement would benefit pilots, farmers, hikers--in short, anyone who uses the Global Positioning System (GPS). Each of the 24+ GPS satellites carries four atomic clocks on board. By triangulating time signals broadcast from orbit, GPS receivers on the ground can pinpoint their own location on Earth
Right: Quantum entanglement does some mind-bending things. In this laser experiment entangled photons are teleported from one place to another.
NASA uses atomic clocks for spacecraft navigation. Geologists use them to monitor continental drift and the slowly changing spin of our planet. Physicists use them to check theories of gravity. An entangled atomic clock might keep time precisely enough to test the value of the Fine Structure Constant, one of the fundamental constants of physics.
Through its office of Biological and Physical Research, NASA recently awarded a grant to Kuzmich and his colleagues to support their research. Kuzmich has studied quantum entanglement for the last 10 years and has recently turned to exploring how it can be applied to atomic clocks.
Einstein never liked entanglement. It seemed to run counter to a central tenet of his theory of relativity: nothing, not even information, can travel faster than the speed of light. In quantum mechanics, all the forces of nature are mediated by the exchange of particles such as photons, and these particles must obey this cosmic speed limit. So an action "here" can cause no effect "over there" any sooner than it would take light to travel there in a vacuum.
But two entangled particles can appear to influence one another instantaneously, whether they're in the same room or at opposite ends of the Universe. Pretty spooky indeed.
Quantum entanglement occurs when two or more particles interact in a way that causes their fates to become linked: It becomes impossible to consider (or mathematically describe) each particle's condition independently of the others'. Collectively they constitute a single quantum state.
Left: Making a measurement on one entangled particle affects the properties of the other instantaneously. Image by Patrick L. Barry.
Two entangled particles often must have opposite values for a property
-- for example, if one is spinning in "up" direction, the
other must be spinning in the "down" direction. Suppose
you measure one of the entangled particles and, by doing so, you nudge
it "up." This causes the entangled partner to spin "down."
Making the measurement "here" affected the other particle "over there"
instantaneously, even if
the other particle was a million miles away.
While physicists and philosophers grapple with the implications for the nature of causation and the structure of the Universe, some physicists are busy putting entanglement to work in applications such as "teleporting" atoms and producing uncrackable encryption.
At the heart of every atomic clock lies a cloud of atoms, usually cesium or rubidium. The natural resonances of these atoms serve the same purpose as the pendulum in a grandfather clock. Tick-tock-tick-tock. A laser beam piercing the cloud can count the oscillations and use them to keep time. This is how an atomic clock works.
Right: Lasers are a key ingredient of atomic clocks--both the ordinary and entangled variety. Click on the image to learn more.
"The best atomic clocks on Earth today are stable to about one part in 1015," notes Kuzmich. That means an observer would have to watch the clock for 1015 seconds or 30 million years to see it gain or lose a single second.
The precision of an atomic clock depends on a few things, including the number of atoms being used. The more atoms, the better. In a normal atomic clock, the precision is proportional to the square-root of the number of atoms. So having, say, 4 times as many atoms would only double the precision. In an entangled atomic clock, however, the improvement is directly proportional to the number of atoms. Four times more atoms makes a 4-times better clock.
Using plenty of atoms, it might be possible to build a "maximally entangled clock stable to about one part in 1018," says Kuzmich. You would have to watch that clock for 1018 seconds or 30 billion years to catch it losing a single second.
Kuzmich plans to use the lasers already built-in to atomic clocks to create the entanglement.
"We will measure the phase of the laser light passing through the cloud of atoms," he explains. Measuring the phase "tweaks the laser beam," and if the frequency of the laser has been chosen properly, tweaking the beam causes the atoms to become entangled. Or, as one quantum physicist might say to another, "such a procedure amounts to a quantum non-demolition (QND) measurement on the atoms, and results in preparation of a Squeezed Spin State."
Above: Georgia Institute of Technology professor of physics Alex Kuzmich.
How soon an entangled clock could be built--much less launched into
space aboard a hypothetical new generation of GPS satellites--is difficult
to predict, cautions Kuzmich. The research is still at the stage of
just demonstrating the principle. Building a working prototype is
probably several years away.
But thanks to research such as this, having still-better atomic clocks available to benefit science and technology is only a matter of time.
Tick-Tock Atomic Clock -- (Science@NASA) Scientists are building atomic clocks that keep time with mind-boggling precision. Such devices will help farmers, physicists, and interstellar travelers alike.
NASA's Office of Biological and Physical Research supports studies of fundamental physics for the benefit of people on Earth and in space.
What is an atomic second?In an atomic clock,
the steady "tick" of an electronic oscillator is kept steady by comparing
it to the natural frequency of an atom -- usually cesium-133. When
a cesium atom drops from one particular energy level to another, a
microwave photon emerges. The wave-like photon oscillates like a pendulum
in an old-style clock. When it has oscillated precisely 9,192,631,770
times -- by decree of the Thirteenth General
Conference on Weights and Measures in 1967 -- we know that one "atomic
second" has elapsed.
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From UPSC perspective, the following things are important :
Prelims level : Qubit, superposition.
Mains level : Paper 3- What do you understand by quantum technology? What are its applications? How it is different from the classical computer technology?
The article suggests that the corona crisis would speed up research in the field of quantum computing. The tremendous speed offered by quantum computers will help us find a cure for diseases like Covid-19 in a much shorter duration. This article explains the limitations of classical computers, working of quantum technology, and how quantum computer overcomes these limitations.
Use of supercomputer to find the cure of Covid-19
- The whole world is pressurized into quickly discovering a vaccine and a cure for covid-19.
- IBM’s Summit, the world’s fastest supercomputer, was used for running numerous simulations and computations.
- These simulations and computations help scientists find promising molecules to fight the pandemic.
- The latest update says the Summit has been able to identify 77 candidate molecules that researchers can use in trials.
- This was achieved in just two days, while, traditionally, it has taken months to make such progress.
Computing capacity as a limit on molecular discoveries
- Today, faster molecular discoveries are limited by computing capacity.
- Molecular discoveries are also limited by the need for scientists to write codes for harnessing the computing power.
- It is no secret that classical computing power is plateauing (e. it is not growing anymore)
- And till we have scalable artificial intelligence (AI) and machine learning (ML), scientists will have to write code for not only different scenarios but also for different computing platforms.
- So, what we need today is more computing power.
The following points explain the limits of classical computers. Pay attention to the Moore’s law, and how it explains the development of semiconductor technologies and in turn computers as a whole.
What is the solution to the limits of classical computers?
- Given that we have already neared the peak of classical computing, the solution probably is quantum computing.
- Not just vaccines, quantum computing can accelerate many innovations, such as hyper-individualized medicines, 3-D printed organs, search engines for the physical world etc.
- All innovations currently constrained by the size of transistors used in classical computing chips can be unleashed through quantum computing.
- Moore’s law: In 1965, Gordon Moore had said the number of transistors that can be packed into a given unit of space will double about every two years.
- Subsequently, in an interview in 2005, he himself admitted that this law can’t continue forever.
- He had said: “It is the nature of exponential functions, they eventually hit a wall.”
- Over the last 60 years, we reaped the benefits of Moore’s law in many ways.
- For instance, compared to initial days of the Intel 4004, the modern 14nm processors deliver way bigger impact—3,500 times better performance and 90,000 times improved efficiency, at 1/60,000th the cost!
- Yet, we are also seeing his 2005 statement coming true. All the experts agree that the ‘wall’ is very near.
- So, what next? The answer again is probably the same—quantum computing.
Quantum technology is one of the emerging and revolutionary technologies, you should be aware of the terms and general principle which lies at the heart of such technology. So, terms like superposition, qubit, binary etc are important if you want to answer a questions related to this technology.
Quantum computing and its applications
- It is no more a concept, there are working models available on the cloud.
- How it works: Quantum computing uses the ability of sub-atomic particles to exist in multiple states simultaneously, until it is observed.
- The concept of qubits: Unlike classical computers that can store information in just two values, that is 1 or 0, quantum computing uses qubits that can exist in any superposition of these values,
- This superposition enables quantum computers to solve in seconds problems which a classical computer would take thousands of years to crack.
- Applications: The application of this technology is enormous, and just to cite a few, it can help with the discovery of new molecules, optimize financial portfolios for different risk scenarios.
- It can also crack RSA encryption keys, detect stealth aircraft, search massive databases in a split second and truly enable AI.
Investment in the development of technology
- In the Union budget this year, the Indian government announced investments of ₹8,000 crores for developing quantum technologies and applications.
- Globally, too, countries and organizations are rushing to develop this technology and have already invested enormous capital towards its research.
Historically, unprecedented crises have always created more innovations than routine challenges or systematic investments. Coincidentally, current times pose similar opportunities in disguise for the development of quantum technologies.
Back2Basics: Difference between bit and qubit
- A binary digit, characterized as 0 and 1, is used to represent information in classical computers.
- A binary digit can represent up to one bit of information, where a bit is the basic unit of information.
- In classical computer technologies, a processed bit is implemented by one of two levels of low DC voltage.
- And whilst switching from one of these two levels to the other, a so-called forbidden zone must be passed as fast as possible, as electrical voltage cannot change from one level to another instantaneously.
- There are two possible outcomes for the measurement of a qubit—usually taken to have the value “0” and “1”, like a bit or binary digit.
- However, whereas the state of a bit can only be either 0 or 1, the general state of a qubit according to quantum mechanics can be a coherent superposition of both.
- Moreover, whereas a measurement of a classical bit would not disturb its state, a measurement of a qubit would destroy its coherence and irrevocably disturb the superposition state.
- It is possible to fully encode one bit in one qubit.
- However, a qubit can hold more information, e.g. up to two bits using superdense coding.
- For a system of n components, a complete description of its state in classical physics requires only n bits, whereas in quantum physics it requires 2n−1 complex numbers.


A decade ago, quantum computing was still something of a parlor game. Quantum-computer advocates could make bold claims about one promising technology or another because no one had yet figured out how to string together more than a handful of quantum bits (qubits).
Times have changed. IBM now has a 50-qubit machine, Intel is at 49 qubits, and Google has developed a 72-qubit device. And in September, Pennsylvania State University researchers announced they’d built the framework for a 125-qubit compute engine.
However, unlike the more mature devices from IBM, Intel, and Google, the foundational element for the proof-of-concept Penn State system is not the computer chip but rather the atomic clock.
The neutral-atom quantum computer, proposed by the Penn State group and other researchers around the world, uses a cesium atom in a laser trap (the gold standard of precision timekeeping) as the quantum bit on which the compute engine is based.
“There’s no quantum-mechanical system we understand better than an atom,” says David Weiss, a professor of physics at Penn State. His group published a paper in Nature announcing that they’d used lasers to suspend and cool 125 cesium atoms in the shape of a cube, with each atom held 5 micrometers from its nearest neighbors. (The qubits can be loaded, cooled, and shielded from interference. But the group hasn’t yet developed the logic gates or error correction necessary to make it run.)
Atomic clocks use a well-studied characteristic of these ultracooled and stabilized atoms as the basis for a tick to mark the passage of time. Called the hyperfine split, it involves the spin of each atom’s outermost electron. (One second is universally defined today as 9,192,631,770 periods of the radiation given off from the hyperfine split in cesium.)
For a quantum computer, the idea is to use the same set of cesium quantum states used by an atomic clock. But the cesium atoms, as part of a quantum computer, rely on a quantum property not used in the atomic clock. Like all qubits, those in the cesium-atom quantum computer can occupy one hyperfine state (call it 0) or a slightly higher energy state (call it 1) or, at the core of quantum computing, an in-between state that’s a little bit 0 and a little bit 1, called quantum superposition.
To perform quantum computations using an array of atoms, the atoms must be entangled. To achieve this, Weiss explains, lasers carefully kick an individual atom inside the 125-qubit 3D array into a highly excited electronic state and then cool it back down. The entire system is so sensitive, he says, that cesium atoms near the target atom sense its excitation and de-excitation, which is enough to entangle at least a portion of the atoms in the array.
Atomic Order: These images show various configurations of cesium atoms held by lasers in a grid. The presence of an illuminated dot indicates an atom is trapped in place. The absence of a dot indicates an empty parking space. Image: Weiss Laboratory/Penn State
Mark Saffman, a physics professor at the University of Wisconsin–Madison, says his group’s 2D arrays of trapped cesium atoms can maintain their delicate quantum states for 10 seconds or more (Saffman notes that this figure comes from Weiss’s research team). By contrast, a typical operation (say, multiplying one set of qubits by another) might take a microsecond or less. So the potential is inherent in the system, Saffman says, to run many operations before its quantum states collapse due to noise. “By exciting these atomic qubits to highly excited states using laser beams, we can turn on, at will, very strong interactions,” he says.
There are still trade-offs that make neutral-atom quantum computing a challenge, says William Phillips, a physics professor at the University of Maryland and cowinner of the 1997 Nobel Prize in Physics for his work on laser atom traps.
“The lack of long-range, strong Coulomb interactions means that it is easier to put lots of atoms into a small volume, but it also means that it is harder to manipulate the atoms—that is, to perform quantum gates rapidly,” Phillips says.
Yet, says Dana Anderson, CEO of Boulder, Colo.–based ColdQuanta, now that individual atoms can be reliably stabilized and cooled to below 100 nanokelvins, much of the fundamental science is in place. Anderson says ColdQuanta is working to realize Saffman and Weiss’s vision of neutral atoms as the basis for quantum computers or simulators.
“Once you can get atoms down that cold, we have line of sight to a lot of quantum technologies,” Anderson says. “Whether we’re doing a quantum clock or quantum computing, it’s the same stuff that goes inside.”
Weiss says his 3D array could possibly scale up to 1,728 qubits, arranged in 12 columns and rows, with current technology. However, little could be done with so many qubits until his group and others develop stronger error-correction measures.
And whether Weiss’s 3D arrays or the 2D arrays preferred by Saffman and ColdQuanta are more feasible in the long term remains an open question. For now, “I recognize these problems to be solvable,” Anderson says. “It’s very much an engineering challenge.”
This article appears in the December 2018 print issue as “Atomic Clocks Inspire New Qubits.”


Physicists at JILA have for the first time observed chemical reactions near absolute zero, demonstrating that chemistry is possible at ultralow temperatures and that reaction rates can be controlled using quantum mechanics, the peculiar rules of submicroscopic physics.
The new results and techniques, described in the Feb. 12 issue of Science,* will help scientists understand previously unknown aspects of how molecules interact, a key to advancing biology, creating new materials, producing energy and other research areas. The new JILA work also will aid studies of quantum gases (in which particles behave like waves) and exotic physics spanning the quantum and macroscopic worlds. It may provide practical tools for “designer chemistry” and other applications such as precision measurements and quantum computing
Scientists have long known how to control the internal states of molecules, such as their rotational and vibrational energy levels. In addition, the field of quantum chemistry has existed for decades to study the effects of the quantum behavior of electrons and nuclei—constituents of molecules. But until now scientists have been unable to observe direct consequences of quantum mechanical motions of whole molecules on the chemical reaction process. Creating simple molecules and chilling them almost to a standstill makes this possible by presenting a simpler and more placid environment that can reveal subtle, previously unobserved chemical phenomena.
By precisely controlling the ultracold molecules’ internal states—electronic energy levels, vibrations, rotations and nuclear spin (or angular momentum)—while also controlling the molecular motions at the quantum level, JILA scientists can study how the molecules scatter or interact with each other quantum mechanically. They were able to observe how the quantum effects of the molecule as a whole dictate reactivity. This new window into molecular behavior has allowed the observation of long-range interactions in which quantum mechanics determines whether two molecules should come together to react or stay apart. Thus the JILA work pushes the field in new directions and expands the standard conception of chemistry.
The JILA quantum chemistry experiments were performed with a gas containing up to 1 trillion molecules per cubic centimeter at temperatures of a few hundred billionths of a Kelvin (nanokelvins) above absolute zero (minus 273 degrees Celsius or minus 459 degrees Fahrenheit). Each molecule consists of one potassium atom and one rubidium atom. The molecules have a negative electric charge on the potassium side and a positive charge on the rubidium side, so they can be controlled with electric fields.
By measuring how many molecules are lost over time from a gas confined inside a laser-based optical trap, at different temperatures and under various other conditions, the JILA team found evidence of heat-producing chemical reactions in which the molecules must have exchanged atoms, broken chemical bonds, and forged new bonds. Theoretical calculations of long-range quantum effects agree with the experimental observations.
In conventional chemistry at room temperature, molecules may collide and react to form different compounds, releasing heat. In JILA’s ultracold experiments, quantum mechanics reigns and the molecules spread out as ethereal rippling waves instead of acting as barbell-like solid particles. They do not collide in the conventional sense. Rather, as their quantum mechanical wave properties overlap, the molecules sense each other from as much as 100 times farther apart than would be expected under ordinary conditions. At this distance the molecules either scatter from one another or, if quantum conditions are right, swap atoms. Scientists expect to be able to control long-range interactions by creating molecules with specific internal states and “tuning” their reaction energies with electric and magnetic fields.
The JILA team produced a highly dense molecular gas and found that, although molecules move slowly at ultralow temperatures, reactions can occur very quickly. However, reactions can be suppressed using quantum mechanics. For instance, a cloud of molecules in the lowest-energy electronic, vibrational and rotational states reacts differently if the nuclear spins of some molecules are flipped. If a cloud of molecules is divided 50/50 into two different nuclear spin states, reactions proceed 10 to 100 times faster than if all molecules possess the same spin state. Thus, by purifying the gas (by preparing all molecules in the same spin state), scientists can deliberately suppress reactions.
The JILA experimental team attributes these results to the fact the molecules are fermions, one of two types of quantum particles found in nature. (Bosons are the second type.) Two identical fermions cannot be in the same place at the same time. This quantum behavior of fermions manifests as a suppression of the chemical reaction rate in the ultralow temperature gas. That is, molecules with identical nuclear spins are less likely to approach each other and react than are particles with opposite spins.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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