China to build world-leading national laboratory for quantum information sciences



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China is planning to build a massive 100-billion-yuan national laboratory for #quantum information sciences, in order to establish itself as a leader in quantum information sciences.

The National Laboratory for Quantum Information Sciences, which will be spread across Shanghai and Beijing and cities in Anhui province, will focus on the frontier science and key technology of the second quantum revolution, and develop strategic emerging industries covering quantum communication, computation, and precision measurement, so as to become a pioneer in the global competition and future  development of QIS, news portal CBN reported.
The information was revealed at the 2018 International Conference on Quantum Cryptography in Shanghai in August.  The project has allegedly received 2 billion yuan in financial support from the city of Shanghai and Anhui province.
The conference marked the first time for China to hold such an influential international academic event in the field of quantum cryptography, boosting the development of the country’s quantum communications network.
QIS can further improve information security, computing speed, and measurement accuracy, as so to provide core strategic power for national security and sustainable development.
China has been leading the global quantum revolution after the successful launch of
the Quantum Experiments at Space Scale, the world’s first quantum satellite, and the construction of the 2,000-kilometer Beijing-Shanghai quantum communication line.The market volume of China’s quantum communication industry reached 18 billion yuan in 2017, and is expected to reach 32 billion yuan in 2018, with a year-on-year increase of 77.78%, according to data from Qianzhan Industry Research Institute, the
most influential industry research and innovation consulting brand in China.

People’s Daily, China

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Academy of Sciences, and his colleagues announced they have built world’s first quantum computing machine at a press conference in the Shanghai Institute for Advanced Studies of University of Science and Technology of China on Wednesday. — People’s Daily

 

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Chinese scientists make quantum leap in computing; jumbo passenger jet C919 liftoff !


Chinese leading quantum physicist Pan Jianwei, an academician of the Chinese Academy of Sciences, and his colleagues announced they have built world’s first quantum computing machine at a press conference in the Shanghai Institute for Advanced Studies of University of Science and Technology of China on Wednesday. — People’s Daily

CHINESE scientists have built the world’s first quantum computing machine that goes far beyond the early classical — or conventional — computers, paving the way to the ultimate realization of quantum computing.

Scientists announced their achievement at a press conference in the Shanghai Institute for Advanced Studies of University of Science and Technology of China on Wednesday.

Scientists believe quantum computing could in some ways dwarf the processing power of today’s supercomputers. One analogy to explain the concept of quantum computing is that it is like being able to read all the books in a library at the same time, whereas conventional computing is like having to read them one after another.

Pan Jianwei, an academician of the Chinese Academy of Sciences and a leading quantum physicist, said quantum computing exploits the fundamental quantum superposition principle to enable ultra-fast parallel calculation and simulation capabilities.

In normal silicon computer chips, data is rendered in one of two states: 0 or 1. However, in quantum computers, data could exist in both states simultaneously, holding exponentially more information.

The computing power of a quantum computer grows exponentially with the number of quantum bits that can be manipulated. This could effectively solve large-scale computation problems that are beyond the ability of current classical computers, Pan said.

For example, a quantum computer with 50 quantum bits would be more powerful in solving quantum sampling problems than today’s fastest supercomputer, Sunway TaihuLight, installed in the National Supercomputing Center of China.

Due to the enormous potential of quantum computing, Europe and the United States are actively collaborating in their research. High-tech companies, such as Google, Microsoft and IBM, also have massive interests in quantum computing research.

The research team led by Pan is exploring three technical routes: systems based on single photons, ultra-cold atoms and superconducting circuits.

Recently, Pan Jianwei and his colleagues — Lu Chaoyang and Zhu Xiaobo, of the University of Science and Technology of China, and Wang Haohua, of Zhejiang University — set two international records in quantum control of the maximal numbers of entangled photonic quantum bits and entangled superconducting quantum bits.

Pan explained that manipulation of multi-particle entanglement is the core of quantum computing technology and has been the focus of international competition in quantum computing research.

In the photonic system, his team has achieved the first 5, 6, 8 and 10 entangled photons in the world and is at the forefront of global developments.

Pan said quantum computers could, in principle, solve certain problems faster than classical computers. Despite substantial progress in the past two decades, building quantum machines that can actually outperform classical computers in some specific tasks — an important milestone termed “quantum supremacy” — remains challenging.

In the quest for quantum supremacy, Boson sampling, an intermediate (that is, non-universal) quantum computer model, has received considerable attention, as it requires fewer physical resources than building universal optical quantum computers, Pan said.

Last year, Pan and Lu Chaoyang developed the world’s best single photon source based on semiconductor quantum dots. Now, they are using the high-performance single photon source and electronically programmable photonic circuit to build a multi-photon quantum computing prototype to run the Boson sampling task.

The test results show the sampling rate of this prototype is at least 24,000 times faster than international counterparts, according to Pan’s team.

At the same time, the prototype quantum computing machine is 10 to 100 times faster than the first electronic computer, ENIAC, and the first transistor computer, TRADIC, in running the classical algorithm, Pan said.

It is the first quantum computing machine based on single photons that goes beyond the early classical computer, and ultimately paves the way to a quantum computer that can beat classical computers. This achievement was published online in the latest issue of Nature Photonics this week.

In the superconducting quantum circuit system, a research team from Google, NASA and the University of California at Santa Barbara announced a high-precision manipulation of 9 superconducting quantum bits in 2015.

Now the Chinese team led by Pan, Zhu Xiaobo and Wang Haohua have broken that record. They independently developed a superconducting quantum circuit containing 10 superconducting quantum bits and successfully entangled the 10 quantum bits through a global quantum operation.

Chinese scientists aim to realize manipulation of 20 entangled photons by the end of this year, and will try to design and manipulate 20 superconducting quantum bits. They also plan to launch a quantum cloud computing platform by the end of this year.

Source: Xinhua

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China successfully launches world’s first quantum communication satellite ‘very exciting’ !


Combined photo shows China launching the world’s first quantum satellite on top of a Long March-2D rocket from the Jiuquan Satellite Launch Center in Jiuquan, northwest China’s Gansu Province, Aug. 16, 2016. The world’s first quantum communication satellite, which China has launched, has been given the moniker “Micius,” after a fifth century B.C. Chinese scientist, the Chinese Academy of Sciences (CAS) announced Monday. (Xinhua/Jin Liwang)

WASHINGTON, Aug. 15 — China’s successful launch of the world’s first quantum satellite was “very exciting” and can help conduct experiments that may lead to “much more secure” quantum communications, a U.S. quantum expert said.

“The event is indeed very exciting and does carry global importance because this would be the first such experiment,” said Alexander Sergienko, a professor of electrical and computer engineering at the Boston University.

The satellite, Quantum Experiments at Space Scale (QUESS), lifted off from China’s Jiuquan Satellite Launch Center at 1:40 a.m. Tuesday, local time.

Sergienko said the quantum communication race has been going on for the last 20 years since the initial demonstration of quantum key distribution link under Lake Geneva in 1995.

After that, metropolitan secure communication networks have been developed and demonstrated in Boston, Vienna, Beijing, and Tokyo, and many more examples of quantum metropolitan networks have been demonstrated in the last five years covering Canada, Italy, U.K. and Australia, he said.

“The race is now moving in the near space in order to cover longer distances between different metropolitan areas,” he said.

“I know there were plans to develop multiple point-by-point multi-city quantum communication segments to cover the distance between Shanghai and Beijing. A successful implementation of the satellite project would allow covering it in one step.”

Sergienko also predicted that quantum communication and cryptography will be first used to ensure the most important communication lines such as used by the government and by major business in their communication.

China said the 600-plus-kilogram QUESS, nicknamed “Micius,” is expected to circle the Earth once every 90 minutes after it enters a sun-synchronous orbit at an altitude of 500 kilometers.

In its two-year mission, QUESS is designed to establish “hack-proof” quantum communications by transmitting uncrackable keys from space to the ground, and provide insights into the strangest phenomenon in quantum physics — quantum entanglement.

China launches first-ever quantum communication satellite

China launches the world’s first quantum satellite on top of a Long March-2D rocket from the Jiuquan Satellite Launch Center in Jiuquan, northwest China’s Gansu Province, Aug. 16, 2016. The world’s first quantum communication satellite, which China is preparing to launch, has been given the moniker “Micius,” after a fifth century B.C. Chinese scientist, the Chinese Academy of Sciences (CAS) announced Monday. (Xinhua/Jin Liwang)

China successfully launched the world’s first quantum satellite from the Jiuquan Satellite Launch Center in northwestern Gobi Desert at 1:40 am on Tuesday.

In a cloud of thick smoke, the satellite, Quantum Experiments at Space Scale (QUESS), roared into the dark sky on top of a Long March-2D rocket.

The 600-plus-kilogram satellite will circle the Earth once every 90 minutes after it enters a sun-synchronous orbit at an altitude of 500 kilometers.

It is nicknamed “Micius,” after a fifth century B.C. Chinese philosopher and scientist who has been credited as the first one in human history conducting optical experiments.

In its two-year mission, QUESS is designed to establish “hack-proof” quantum communications by transmitting uncrackable keys from space to the ground, and provide insights into the strangest phenomenon in quantum physics — quantum entanglement.

Quantum communication boasts ultra-high security as a quantum photon can neither be separated nor duplicated. It is hence impossible to wiretap, intercept or crack the information transmitted through it.

With the help of the new satellite, scientists will be able to test quantum key distribution between the satellite and ground stations, and conduct secure quantum communications between Beijing and Xinjiang’s Urumqi.

QUESS, as planned, will also beam entangled photons to two earth stations, 1,200 kilometers apart, in a move to test quantum entanglement over a greater distance, as well as test quantum teleportation between a ground station in Ali, Tibet, and itself.

“The newly-launched satellite marks a transition in China’s role — from a follower in classic information technology (IT) development to one of the leaders guiding future IT achievements,” said Pan Jianwei, chief scientist of QUESS project with the Chinese Academy of Sciences (CAS).

The scientists now are expecting quantum communications to fundamentally change human development in the next two or three decades, as there are enormous prospects for applying the new generation of communication in fields like defense, military and finance. SPOOKY & ENTANGLED

Quantum physics is the study of the basic building blocks of the world at a scale smaller than atoms. These tiny particles behave in a way that could overturn assumptions of how the world works.

One of the strange properties of quantum physics is that a tiny particle acts as if it’s simultaneously in two locations — a phenomenon known as “superposition.” The noted interpretation is the thought experiment of Schrodinger’s cat — a scenario that presents a cat that may be simultaneously both alive and dead.

If that doesn’t sound strange enough, quantum physics has another phenomenon which is so confounded that Albert Einstein described as “spooky action at a distance” in 1948.

Scientists found that when two entangled particles are separated, one particle can somehow affect the action of the far-off twin at a speed faster than light.

Scientists liken it to two pieces of paper that are distant from each other: if you write on one, the other immediately shows your writing.

In the quantum entanglement theory, this bizarre connection can happen even when the two particles are separated by the galaxy.

By harnessing quantum entanglement, the quantum key technology is used in quantum communications, ruling out the possibility of wiretapping and perfectly securing the communication.

A quantum key is formed by a string of random numbers generated between two communicating users to encode information. Once intercepted or measured, the quantum state of the key will change, and the information being intercepted will self-destruct.

According to Pan, scientists also plan to test quantum key distribution between QUESS and ground stations in Austria. Italy, Germany and Canada, as they have expressed willingness to cooperate with China in future development of quantum satellite constellations, said Pan. LIFE CHANGING

With the development of quantum technology, quantum mechanics will change our lives in many ways. In addition to quantum communications, there are quantum computers that have also drawn attentions from scientists and governments worldwide.

Quantum computing could dwarf the processing power of today’s supercomputers.

In normal silicon computer chips, data is rendered in one of two states: 0 or 1. However, in quantum computers, data could exist in both states simultaneously, holding exponentially more information.

One analogy to explain the concept of quantum computing is that it is like being able to read all the books in a library at the same time, whereas conventional computing is like having to read them one after another.

Scientists say that a quantum computer will take just 0.01 second to deal with a problem that costs Tianhe-2, one of the most powerful supercomputers in the world, 100 years to solve.

Many, however, is viewing this superpower as a threat: if large-scale quantum computers are ever built, they will be able to crack all existing information encryption systems, creating an enormous security headache one day.

Therefore, quantum communications will be needed to act like a “shield,” protecting information from the “spear” of quantum computers, offering the new generation of cryptography that can be neither wiretapped nor decoded. GOING GLOBAL?

With the launch of QUESS, Chinese scientists now are having their eyes on a ground-to-satellite quantum communication system, which will enable global scale quantum communications.

In past experiments, quantum communications could only be achieved in a short range, as quantum information, in principle, could travel no more than 500 kilometers through optical fibers on the land due to the loss of photons in transmission, Pan explained.

Since photons carrying information barely get scattered or absorbed when travelling through space and Earth’s atmosphere, said Pan, transmitting photons between the satellite and ground stations will greatly broaden quantum communications’reach.

However, in quantum communications, an accurate transmission of photons between the “server” and the “receiver” is never easy to make, as the optic axis of the satellite must point precisely toward those of the telescopes in ground stations, said Zhu Zhencai, QUESS chief designer.

It requires an alignment system of the quantum satellite that is 10 times as accurate as that of an ordinary one and the detector on the ground can only catch one in every one million entangled photons fired, the scientist added.

What makes it much harder is that, at a speed of eight kilometers per second, the satellite flying over the earth could be continuously tracked by the ground station for merely a few minutes, scientists say.

“It will be like tossing a coin from a plane at 100,000 meters above the sea level exactly into the slot of a rotating piggy bank,” said Wang Jianyu, QUESS project’s chief commander.

Given the high sensitivity of QUESS, people could observe a match being lit on the moon from the Earth, Wang added.

After years of experimenting, Chinese scientists developed the world’ s first-ever quantum satellite without any available reference to previous projects. Now they are waiting to see QUESS’s performance in operation.

According to Pan, his team has planned to initiate new projects involving research on quantum control and light transmission in space station, as well as tests on quantum communications between satellites, all-time quantum communications and the application of quantum key network.

“If China is going to send more quantum communication satellites into orbit, we can expect a global network of quantum communications to be set up around 2030,” said Pan. – Xinhuanet

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World’s first Quantum communication satellite to be launched in China against hackers


China is poised to become the first country to send encoded information from space that cannot be hacked. Scientists are making final adjustments to China’s first quantum communication satellite. The project chief describes it as a revolution in communications.

China will launch its first experimental quantum communication satellite in July, according to the Chinese Academy of Sciences.

 

China is poised to become the first country to send encoded information from space that cannot be hacked. Scientists are making final adjustments to China’s first quantum communication satellite. The project chief describes it as a revolution in communications.

A quantum photon cannot be separated or duplicated, which means if someone tried to decode information, the encryption would change, and the receiver would know that his letter was opened by someone.

Scientists hope the new technology will protect China from future cyber issues. In 2015, cases involving information technology in China rose by more than 120 percent, according to survey by a non-profit cybersecurity institution. China plans to use its quantum satellite system to cover the planet by 2030.

On the ground, China is also building its own quantum information sharing network for use in national defense and security. At some point, China plans to connect the ground network to the quantum satellite system.

It has taken five years for Chinese scientists to develop and manufacture the first quantum satellite. In June, it will be transported to the Jiuquan Satellite Launch Center in southwest China for final preparation and launch in July., 2016

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Quantum Computing? Quantum Bar Magnets in a Transparent Salt


ScienceDaily (June 15, 2012) — Scientists have managed to switch on and off the magnetism of a new material using quantum mechanics, making the material a test bed for future quantum devices.

This image shows the antiferromagnetic arrangement of the spins (colored arrows) in the magnetic salt used by the Swiss-German-US-London team. (Credit: University College London)

The international team of researchers led from the Laboratory for Quantum Magnetism (LQM) in Switzerland and the London Centre for Nanotechnology (LCN), found that the material, a transparent salt, did not suffer from the usual complications of other real magnets, and exploited the fact that its quantum spins — which are like tiny atomic magnets — interact according to the rules of large bar magnets. The study is published in Science.

Anybody who has played with toy bar magnets at school will remember that opposite poles attract, lining up parallel to each other when they are placed end to end, and anti-parallel when placed adjacent to each other. As conventional bar magnets are simply too large to reveal any quantum mechanical nature, and most materials are too complex for the spins to interact like true bar magnets, the transparent salt is the perfect material to see what’s going on at the quantum level for a dense collection of tiny bar magnets.

The team were able to image all the spins in the special salt, finding that the spins are parallel within pairs of layers, while for adjacent layer pairs, they are antiparallel, as large bar magnets placed adjacent to each other would be. The spin arrangement is called “antiferromagnetic.” In contrast, for ferromagnets such as iron, all spins are parallel.

By warming the material to only 0.4 degrees Celsius above the absolute “zero” of temperature where all classical (non-quantum) motion ceases, the team found that the spins lose their order and point in random directions, as iron does when it loses its ferromagnetism when heated to 870 Celsius, much higher than room temperature because of the strong and complex interactions between electron spins in this very common solid.

The team also found that they could achieve the same loss of order by turning on quantum mechanics with an electromagnet containing the salt. Thus, physicists now have a new toy, a collection of tiny bar magnets, which naturally assume an antiferromagnetic configuration and for which they can dial in quantum mechanics at will.

“Understanding and manipulating magnetic properties of more traditional materials such as iron have of course long been key to many familiar technologies, from electric motors to hard drives in digital computers,” said Professor Gabriel Aeppli, UCL Director of the LCN.

“While this may seem esoteric, there are deep connections between what has been achieved here and new types of computers, which also rely on the ability to tune quantum mechanics to solve hard problems, like pattern recognition in images.”

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‘Quantum criticality’: Ultracold experiments heat up quantum research


Ultracold experiments heat up quantum research

Enlarge

This false color image shows the average density of cesium atoms taken during multiple experimental cycles for studying quantum criticality in the ultracold laboratory of Cheng Chin, associate professor in physics at UChicago. The density is lowest in the white area on the outside, highest toward the center, where higher numbers of atoms are blocking the incoming infrared laser light. Xibo Zhang collected these data in connection with his recently completed doctoral research at UChicago. (Xibo Zhang and Cheng Chin)

(PhysOrg.com) — University of Chicago physicists have experimentally demonstrated for the first time that atoms chilled to temperatures near absolute zero may behave like seemingly unrelated natural systems of vastly different scales, offering potential insights into links between the atomic realm and deep questions of cosmology.

This ultracold state, called “ criticality,” hints at similarities between such diverse phenomena as the gravitational dynamics of black holes or the exotic conditions that prevailed at the birth of the universe, said Cheng Chin, associate professor in physics at UChicago. The results could even point to ways of simulating cosmological phenomena of the early universe by studying systems of in states of .

“Quantum criticality is the entry point for us to make connections between our observations and other systems in nature,” said Chin, whose team is the first to observe quantum criticality in ultracold atoms in optical lattices, a regular array of cells formed by multiple laser beams that capture and localize individual atoms.

UChicago graduate student Xibo Zhang and two co-authors published their observations online Feb. 16 in Science Express and in the March 2 issue of Science.

Quantum criticality emerges only in the vicinity of a quantum phase transition. In the physics of everyday life, rather mundane phase transitions occur when, for example, water freezes into ice in response to a drop in . The far more elusive and exotic quantum phase transitions occur only at ultracold temperatures under the influence of magnetism, pressure or other factors.

“This is a very important step in having a complete test of the theory of quantum criticality in a system that you can characterize and measure extremely well,” said Harvard University physics professor Subir Sachdev about the UChicago study.

have extensively investigated quantum criticality in crystals, superconductors and magnetic materials, especially as it pertains to the motions of electrons. “Those efforts are impeded by the fact that we can’t go in and really look at what every electron is doing and all the various properties at will,” Sachdev said.

Sachdev’s theoretical work has revealed a deep mathematical connection between how subatomic particles behave near a quantum critical point and the gravitational dynamics of black holes. A few years hence, offshoots of the Chicago experiments could provide a testing ground for such ideas, he said.

There are two types of critical points, which separate one phase from another. The Chicago paper deals with the simpler of the two types, an important milestone to tackling the more complex version, Sachdev said. “I imagine that’s going to happen in the next year or two and that’s what we’re all looking forward to now,” he said.

Other teams at UChicago and elsewhere have observed quantum criticality under completely different experimental conditions. In 2010, for example, a team led by Thomas Rosenbaum, the John T. Wilson Distinguished Service Professor in Physics at UChicago, observed quantum criticality in a sample of pure chromium when it was subjected to ultrahigh pressures.

Zhang, who will receive his doctorate this month, invested nearly two and a half years of work in the latest findings from Chin’s laboratory. Co-authoring the study with Zhang and Chin were Chen-Lung Hung, PhD’11, now a postdoctoral scientist at the California Institute of Technology, and UChicago postdoctoral scientist Shih-Kuang Tung.

In their tabletop experiments, the Chicago scientists use sets of crossed laser beams to trap and cool up to 20,000 cesium atoms in a horizontal plane contained within an eight-inch cylindrical vacuum chamber. The process transforms the atoms from a hot gas to a superfluid, an exotic form of matter that exists only at temperatures hundreds of degrees below zero.

“The whole experiment takes six to seven seconds and we can repeat the experiment again and again,” Zhang said.

The experimental apparatus includes a CCD camera sensitive enough to image the distribution of atoms in a state of quantum criticality. The CCD camera records the intensity of laser light as it enters that vacuum chamber containing thousands of specially configured ultracold atoms.

“What we record on the camera is essentially a shadow cast by the atoms,” Chin explained.

The UChicago scientists first looked for signs of quantum criticality in experiments performed at ultracold temperatures from 30 to 12 nano-Kelvin, but failed to see convincing evidence. Last year they were able to push the temperatures down to 5.8 nano-Kelvin, just billionths of a degree above (minus 459 degrees Fahrenehit). “It turns out that you need to go below 10 nano-Kelvin in order to see this phenomenon in our system,” Chin said.

Chin’s team has been especially interested in the possibility of using ultracold atoms to simulate the evolution of the early universe. This ambition stems from the quantum simulation concept that Nobel laureate Richard Feynman proposed in 1981. Feynman maintained that if scientists understand one quantum system well enough, they might be able to use it to simulate the operations of another system that can be difficult to study directly.

For some, like Harvard’s Sachdev, quantum criticality in ultracold atoms is worthy of study as a physical system in its own right. “I want to understand it for its own beautiful quantum properties rather than viewing it as a simulation of something else,” he said.

More information: “Observation of Quantum Criticality with Ultracold Atoms in Optical Lattices,” by Xibo Zhang, Chen-Lung Hung, Shih-Kuang Tung, and Chen Chin, Science, March 2, 2012, Vol. 335, No. 6072, pp. 1070-1072, and online Feb. in Science Express Feb. 16.

Provided by University of Chicago (news : web)

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Quantum strategy offers game-winning advantages, even without entangleme


By Lisa Zyga PhysOrg.com.feature Quantum strategy offers game-winning advantages, even without entanglement

Enlarge

Experimental and theoretical results both show that quantum gain – measured as the difference between the winning chances for classical and quantum players – is highest under maximum entanglement. Quantum gain remains even when entanglement disappears, and approaches zero along with the discord. Image credit: Zu, et al. ©2012 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

(PhysOrg.com) — Quantum correlations have well-known advantages in areas such as communication, computing, and cryptography, and recently physicists have discovered that they may help players competing in zero-sum games, as well. In a new study, researchers have found that a game player who uses an appropriate quantum strategy can greatly increase their chances of winning compared with using a classical strategy.

The researchers, Chong Zu from Tsingua University in Beijing, China, and coauthors, have published their study on how mechanics can help in a recent issue of the .

In their study, the researchers focused on a two-player game called matching pennies. In the classical version of this game, each player puts down one penny as either heads or tails. If both pennies match, then Player 1 wins and takes both pennies. If one penny shows heads and the other shows tails, then Player 2 wins and takes both pennies. Since one player’s gain is always the other player’s loss, the game is a zero-sum game.

In the classical version of the game, neither player has any incentive to choose one side of the coin over the other, so players choose heads or tails with equal probability. The random nature of the players’ strategies results in a “mixed strategy Nash equilibrium,” a situation in which each player has only a 50% chance of winning, no matter what strategy they use.

But here, Zu and coauthors have found that a player who has the option of using a quantum strategy can increase his or her chances of winning from 50% to 94%. This quantum version of the game uses entangled photons as qubits instead of pennies. And instead of choosing between heads and tails, players use a polarizer and single-photon detector to implement their strategies. While the classical player can still choose only one of two states, the quantum player has more choices due to her ability to rotate a polarizer 360° before the single-photon detector. The researchers calculated that the quantum player can maximize his or her chances of winning by rotating the polarizer at a 45° angle.

“Each player can apply any operation to their qubit (or coin), and then measure it in computational basis,” Zu explained to PhysOrg.com. “For a classical player, the operation he can do is to flip the bit or just leave it unchanged. However, if a player has quantum power, he can apply arbitrary single-bit operations to his qubit. But the measurement part is the same for the quantum and classical players.”

The researchers found that the quantum advantage depends heavily on how correlated the original photons are, with a maximally entangled state providing the largest gain. The researchers were surprised to find that the quantum advantage doesn’t decrease to zero when entanglement disappears completely, since a different kind of quantum correlation – quantum discord – also provides an advantage. This finding may even be the most interesting part of the study.

“There is no wonder that quantum mechanics will lead to advantages in game theory, but the interesting part of our work is that we find out the quantum gain does not decrease to zero when entanglement disappears,” Zu said. “Instead, it links with another kind of quantum correlation described by discord for the qubit case, and the connection is demonstrated both theoretically and experimentally.”

He added that this finding could potentially be useful for making real-world strategies.

“Our work may help people to understand how works in game theory (in some cases, entanglement is not necessary for a quantum player to achieve a positive gain),” he said. “It may also give a good example of people making strategies in a future quantum network.”

More information: C. Zu, et al. “Experimental demonstration of quantum gain in a zero-sum game.” New Journal of Physics, 14 (2012) 033002. DOI: 10.1088/1367-2630/14/3/033002

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