Chinese Scientists Make Breakthrough in Quantum Computing

[Han Patriot]

A most recent speech made by Pan Jianwei. Pan said his team could achieve the target to manipulate 50 quantum bits within the next 3 to 5 years. And a quantum computer powered by 50 quantum bits manipulation would be faster than the fastest computer today!

Quote of Pan's speech: 除了量子通信外，近年来我们在量子计算等领域也取得了较好的成绩。比如，就在上个月，我们在上海发布了首个超越早期经典计算机的光量子计算原型机，还有首次实现了10个超导量子比特的量子计算芯片。我们预期，再经过3到5年的努力，就可以操纵50个量子比特，这时，量子计算机对某些特定问题的处理能力就可以超过目前最快的经典超级计算机，实现“量子称霸”这一里程碑。

Full speech could be read at (in Chinese only):
http://news.sciencenet.cn/htmlnews/2017/6/380631.shtm?id=380631

Well get it done first. But right now, he has delivered whatever he promised. This guy will get a Nobel prize.

 

[cirr]

Chinese city completes tests of quantum communication network

2017-07-10 09:14

Xinhua Editor: Gu Liping

The quantum communication network is expected to be put into commercial use in the city of Jinan by the end of next month. (Photo/CCTV)

Quantum communication network, which boasts ultra-safe connection impenetrable to hackers, is expected to be put into commercial use in a Chinese city by the end of next month.

Jinan Institute of Quantum Technology announced Sunday that the network, connecting Communist Party and government bodies in Jinan, capital of east China's Shandong Province, had lately been tested and the designers were satisfied with its performance, especially in secured communications.

Liu Hong, a professor with Shandong University who was involved in the test, said the network has proved to be in a "very ideal" condition.

In the test, which involved over 50 programs, the network transmitted data with quantum encryption keys among nearly 200 terminals in the city. Between users, more than 4,000 keys were generated in just a second, said Zhou Fei, an assistant director of the institute.

Quantum communication uses quantum entanglement of photons to make sure that nobody taps into the line, for doing so would inevitably corrupt the signal.

In quantum communication, any interference is detectable. Two parties can exchange secret messages by sharing an encryption key encoded in the properties of entangled particles.

Zhou said the success of the test is a landmark in the development of quantum communication technology worldwide, paving the way for its commercial use first in government and then in finance, energy and other sectors.

http://www.ecns.cn/2017/07-10/264678.shtml

 

[JSCh]

Measuring Out-of-Time-Order Correlators on a Nuclear Magnetic Resonance Quantum Simulator
Jun Li, Ruihua Fan, Hengyan Wang, Bingtian Ye, Bei Zeng, Hui Zhai, Xinhua Peng, and Jiangfeng Du
Phys. Rev. X 7, 031011 – Published 19 July 2017

Popular Summary
Chaos is a phenomenon where system dynamics are extremely sensitive to changes in initial conditions. For decades, physicists have attempted to find chaos in quantum mechanics. Unfortunately, because of the linear nature of quantum theory, such sensitivity does not exist. However, along the way, researchers found that chaos appears in quantum systems in other ways such as information scrambling. Surprisingly, this phenomenon shows up naturally in many branches of physics such as condensed-matter physics, high-energy physics, and quantum information science. This raises the question of how to quantitatively measure information scrambling. A mathematical tool known as an out-of-time-ordered correlation (OTOC) function has recently been identified as a candidate, but it is challenging to observe OTOC in experiments. We have used quantum simulations to demonstrate proof-of-concept measurements of OTOC, with high precision and strong robustness against noise, for the first time.

One of the difficulties in measuring OTOC is its alternating time ordering that requires one to “reverse” the system dynamics. The development of small-scale quantum computers provides a way around this hurdle. We use a four-qubit nuclear-magnetic-resonance quantum processor to simulate the dynamics of other quantum systems. We observe how the OTOC behaves in different scenarios and use the measured OTOC to determine how entropy changes over time.

Our method opens up a way to study OTOC with quantum computers built from other physical systems. The rapid development of quantum computing technology will likely reveal more interesting physics through a unifying understanding of quantum chaos and information scrambling.



Phys. Rev. X 7, 031011 (2017) - Measuring Out-of-Time-Order Correlators on a Nuclear Magnetic Resonance Quantum Simulator

 

[JSCh]

PUBLIC RELEASE: 13-AUG-2018
A new artificial quantum material essential in developing high-efficiency computers
INSTITUTE OF PHYSICS, CAS, CHINA

Scientists at Tsinghua University and Institute of Physics, Chinese Academy of Sciences in Beijing have demonstrated the ability to control the states of matter, thus controlling internal resistance, within multilayered magnetically doped semiconductors using the Quantum Anomalous Hall Effect.

The Quantum Anomalous Hall (QAH) effect occurs in some specially designed materials in which electrons can move a millimeter-scale distance without losing their energy. The ability to apply this effect to devices would allow a new revolution in energy efficiency and computation speed.

In a study published in the journal Chinese Physics Letters, researchers say they have fabricated an artificial material that can be used in developing Topological Quantum Computer using Molecular Beam Epitaxy, a new technique allowing the production of single-molecule-thick layers of crystal to be stacked, and by exploiting the QAH effect.

A quantum computer takes advantage of the ability of subatomic particles to be in multiple states at once (instead of the binary 1 or 0 seen in current computers), allowing them to solve certain types of problems much more efficiently. The Topological Quantum Computer would be a potential further evolution on this. Instead of physical particles, they use a specific type of quasiparticle, called the anyon, to encode the information. Anyons have been found to be highly resistant to errors in both storing and processing information.

"We can indeed realise QAH multilayers, or a stack of multiple layers of crystal lattices that are experiencing the QAH effect, with several magnetically doped films spaced by insulating Cadmium Selenide layers. Since we do it by molecular beam epitaxy, it is easy to control the properties of each layer to drive the sample into different states" says Ke He, a professor at Tsinghua University. Cadmium Selenide is a molecule consisting of one Cadmium atom and one Selenium atom used as a semiconductor; a material whose conductive properties we can modify by adding impurities.

The ability to produce multilayers of thin crystals allows the sandwiching of an insulating film in-between the layers that are conducting electricity, preventing the unwanted interaction of the Electrons between the sheets, similarly to how we try to avoid wires crossing in electronics. These types of structures are very interesting to study because they force some of the electrons into what's called an "edge state" that, until now, were quite difficult to fabricate. This "edge state" serves as a path for a fraction of the electrons to flow through without any resistance, by having many layers stacked on top of each other, the effect becomes amplified by pushing a greater fraction of the electrons into this state.

"By tuning the thicknesses of the QAH layers and Cadmium Selenide insulating layers; we can drive the system into a magnetic Weyl semimetal ... a state of matter that so far has never been convincingly demonstrated in naturally occurring materials."

A Weyl semimetal is an exotic state of matter classified as a solid state crystal that, first observed in July 2015, conducts electricity using the massless "Weyl Fermions", rather than electrons. This significant mass difference between the Weyl Fermions and electrons allows electricity to flow through circuits more effectively, allowing faster devices.

"Now what interests me most is to construct QAH bilayers with the two layers able to be independently controlled. If we could get a pair of counter-propagating edge states, while putting a superconducting contact on the edge of the sample, the two edge states might bind together due to the superconducting contact, leading to Majorana modes which can be used to build a Topological Quantum Computer."

Majorana Modes are thought to be usable in Quantum Error Correcting code, a property unique to topological quantum computers, and an essential part of information theory used to help reduce naturally occurring errors in data transmission and to help counteract the effects of interference. This process is also thought to potentially give them the ability to both process quantum information and store more effectively in the future.


A new artificial quantum material essential in developing high-efficiency computers | EurekAlert! Science News

 

[JSCh]

Finding paves way for even better computers
By Zhang Zhihao | China Daily | Updated: 2018-08-18 08:17

Chinese scientists have discovered new properties of an elusive particle known as Majorana fermion, which has puzzled scientists for more than 80 years, in a more accessible lab environment, paving the way for the next generation of more fault-proof quantum computers. [Photo/IC]

Chinese scientists have discovered new properties of an elusive particle known as Majorana fermion, which has puzzled scientists for more than 80 years, in a more accessible lab environment, paving the way for the next generation of more fault-proof quantum computers.

The particle is named after Italian theoretical physicist Ettore Majorana, who first predicted its existence in 1937. Typically, when a particle－the basic building block of matter－and an antiparticle－its identical twin but with an opposite charge－collide, they will annihilate each other, releasing a burst of energy.

The Majorana fermion, however, is a strange exception that can simultaneously exist as a particle and as its own antiparticle. In 2017, Zhang Shoucheng, a Chinese-American physicist at Stanford University, discovered the fermion using advanced hybrid materials at a temperature close to absolute zero, or-273 C.

The latest discovery was made on iron-based superconductors at a temperature around 4 Kelvin, or -269 C. These requirements are more achievable in common labs using liquid helium, thus reducing the cost of research, Ding Hong, a researcher at the Institute of Physics of the Chinese Academy of Sciences and one of the lead scientists behind the discovery, said on Friday.

Wen Xiaogang, a physicist/professor at the Massachusetts Institute of Technology, said the recent discovery might allow iron-based superconductors to be used in making new quantum computers that are more immune to natural disturbances that could make the machine lose its effectiveness.

Chinese scientists also discovered that in solid matter, a single Majorana fermion can be "captured" and split into two Majorana anyons, Ding said. Anyons are quasiparticles that possess particlelike properties yet do not belong to the family of real particles like protons and neutrons.

The research was published in the journal Science on Friday.

Scientists might be able to use this property to create a new type of quantum computer, called a topological quantum computer, that is more stable than the standard quantum computers currently being researched by tech giants such as Google, IBM and Intel, Ding said.

In March, scientists from Google had tested a world-leading quantum computer processor with 72 quantum bits, or qubits, for data storage and calculations.

Qubits are subatomic particles that can be both 1 and 0 at the same time, unlike conventional computers, including supercomputers, which can only store data in 1 or 0 binary bits.

This strange phenomenon is called quantum superposition. Thanks to this effect, quantum computers' computing power can increase astronomically as the number of qubits used increases, said Zhang Fuchun, a physics professor at the University of Chinese Academy of Sciences.

"However, qubits in today's standard quantum computers are prone to natural disturbances, and can easily lose their data and functions," Zhang said. "So scientists need to protect a single qubit with a hundred other particles, and keep them all at extreme conditions. These can significantly drive up design difficulties and costs."

Since each Majorana fermion can behave like half of a subatomic particle, a single qubit could theoretically be stored in two separated fermions, decreasing the chance of both fermions being disturbed and losing their data, he said.

Dongfei Wang, Lingyuan Kong, Peng Fan, Hui Chen, Shiyu Zhu, Wenyao Liu, Lu Cao, Yujie Sun, Shixuan Du, John Schneeloch, Ruidan Zhong, Genda Gu, Liang Fu, Hong Ding & Hong-Jun Gao. Evidence for Majorana bound states in an iron-based superconductor. Science 16 Aug 2018: DOI: 10.1126/science.aao1797​

 

[JSCh]

Researchers develop multi-purpose silicon chip for quantum information processing
Source: Xinhua| 2018-08-21 00:31:06|Editor: Mu Xuequan


LONDON, Aug. 20 (Xinhua) -- An international team led by UK and Chinese researchers have demonstrated a new multi-functional quantum processor which can be used as a scientific tool to perform a wide array of quantum information experiments, according to a study released Monday by the University of Bristol.

The team has been using silicon photonic chips as a way to try to build quantum computing components on a large scale and the latest result demonstrates it is possible to fully control two qubits of information within a single integrated chip. This means any task that can be achieved with two qubits, can be programmed and realized with the device.

In traditional computers, bits take the form of either being a "1" or a "0", while quantum computers are instead based on "qubits" that can be in a superposition of the "0" and "1" states. Multiple qubits can also be linked in a special way called quantum entanglement. These two quantum physical properties provide the power to quantum computers.

With the newly-developed processor, researchers can not only perform quantum information experiments, but show the way to how fully functional quantum computers might be engineered from large scale fabrication processes.

This is really important. Because one of the challenges of bringing quantum computing technology into real life is how to make a quantum computer in a way that its many parts can be made with very high quality and ultimately at low cost.

"It's a very primitive processor, because it only works on two qubits, which means there is still a long way before we can do useful computations with this technology," said Lead author, Dr Xiaogang Qiang, who undertook the work whilst studying for a PhD at the University of Bristol, and now works in China's National University of Defence Technology.

"But what is exciting is that the different properties of silicon photonics that can be used for making a quantum computer have been combined together in one device," Qiang also said.

The integrated photonics effort started in 2008 and was an answer to the growing concern that individual mirrors and optical elements are just too big and unstable to realize the large complex circuits that a quantum computer will be built.

"We need to be looking at how to make quantum computers out of technology that is scalable, which includes technology that we know can be built incredibly precisely on a tremendous scale," and the team think silicon is a promising material to do this, said Dr Jonathan Matthews, a member of the research team based at the Quantum Engineering Technology Labs at the University of Bristol.

The study has been published in the journal Nature Photonics.

 

[JSCh]

Qubits kept together by shouting at them with microwaves
Microwaves plus clever tricks make qubits more immune to noise.

CHRIS LEE - 10/5/2018, 9:34 PM

Not this kind of microwave, of course.
Matthew Paul Argall

Companies like IBM and Google have leapt at the opportunity to build toy quantum computers. They’ve produced nice interfaces, so you can play quantum computing games. The access frameworks they've provided makes me feel like we are about to break out in useful quantum computers.

The public interface, however, hides the relatively slow progress in solving hardware problems. In particular, qubits don’t live very long, so not much computation can be done. Now, in a very nice bit of work, a team of researchers from China have put together qubits that last about 10-15 times longer.

The case of the vanishing qubits
To get your head around this result, we need to understand three key features of how information is stored and processed in quantum computing. Information is stored in qubits, but a qubit does not just hold a one or a zero; it is really a probability of being a one or a zero. Computations are performed by modifying the probability of a qubit being a one or a zero when it's measured.

A second important point is that, during a computation, the qubit probabilities are all linked to each other: measuring one qubit restricts (or even reveals) the value of the linked qubits.

A third feature is that between computational operations, the probabilities do not stay constant. Instead, they are like swings, oscillating between unity (you will always measure the qubit to be one) and zero (you will always measure the qubit to be zero). Computation depends on measuring at the right time.

Since the qubits are all linked—so they can’t swing back and forth in isolation—they have to swing together, otherwise the linked probabilities between qubits will break. Once they break, you can’t compute anything anymore.

Noise also plays a role. Noise randomly pushes the swings, randomly speeding or slowing them. Each qubit slowly (or not so slowly) moves out of sync with its neighbors. I cannot, based on the amount of time the qubit has been left to swing, predict the probability of a single qubit anymore. Effectively the quantumness of the qubit has gone.

As a result of these issues, the sort of qubit that the researchers in this work used typically lasts about five microseconds. A typical operation takes around 20 nanoseconds. That implies something like less than 300 gate operations before the qubit is useless.

Rocking out to a microwave drum
To keep the qubits in sync with each other, the researchers apply a continuous driving microwave signal. The noise still drives the qubits out of sync, but the effect is much smaller for any given time. Not only that, but applying this trick allows the researchers to use other noise-reducing approaches.

When all of that was applied, the researchers found that their qubit system was stable for at least 36 microseconds. They also showed that they could keep two qubits in sync for more than 60 microseconds while performing gate operations.

The computations also proved to be reliable with high fidelities. The fidelity is the probability of a single operation going right—I perform an operation that should result in a qubit in a specific state, then I check how often I actually get that state. The success rate is the fidelity. The researchers get fidelities are quite high (over 0.97), though not high enough yet. To put it in perspective, after 10 operations, the chance that the qubit is in the target state is only about 70 percent.

The target here is to get single-operation fidelities well over 0.99. If you can do that, then you might be able to accept the occasional error. Multiple runs of the same code should allow the correct result to be determined. If that can’t be achieved, then costly error correction schemes have to be implemented. For these schemes, for every computational qubit, five to nine error correction qubits are required, which is an overhead that we would all love to avoid.

Putting it all together
The technology demonstrated in this paper is, at base, the same as used by IBM (the work presented here is not IBM’s). The architecture has quite a bit of flexibility: qubits can be connected and disconnected from each other, meaning that operations on one qubit don’t add noise to the disconnected qubits.

This research allows qubits to be kept in sync, even while they are disconnected from each other. That extends the number of operations that a quantum computer can perform and reduces the chance that the qubit readout will contain errors.

The researchers also speculate on future improvements for their own flavor of qubit. They think that with some redesign work, it might be possible to get another factor of two increase in the time that the qubits stay in sync. If they can do that, then the fidelities of single gates will get high enough to be very useful.


Qubits kept together by shouting at them with microwaves | Ars Technica

Qiujiang Guo, Shi-Biao Zheng, Jianwen Wang, Chao Song, Pengfei Zhang, Kemin Li, Wuxin Liu, Hui Deng, Keqiang Huang, Dongning Zheng, Xiaobo Zhu, H. Wang, C.-Y. Lu, and Jian-Wei Pan. Dephasing-Insensitive Quantum Information Storage and Processing with Superconducting Qubits. Phys. Rev. Lett. (2018). DOI: 10.1103/PhysRevLett.121.130501​

 

[JSCh]

Huawei Unveils Quantum Computing Simulation HiQ Cloud Service Platform - Huawei
Oct 12, 2018

[Shanghai, China, October 12, 2018] At HUAWEI CONNECT 2018, Huawei has released a cloud service platform for quantum computing simulation — HiQ, which includes a quantum computing simulator and a quantum programming framework on the simulator.

Based on Huawei cloud's powerful computing capability, HiQ provides cloud services with both full and single-amplitude simulations. Specifically, the HiQ platform can simulate quantum circuits with at least 42-qubits for full-amplitude simulations, and at least 81 qubits for single amplitudes. In addition, for low-depth circuits, the qubit number can reach 169 for single-amplitude simulations. It is the best cloud services for quantum circuit simulation. Huawei's HiQ cloud platform for quantum computing simulation will be fully open to the public as an enabling platform for quantum research and education.

HiQ is equipped with a distributed architecture and an algorithmic optimizer to overcome challenges associated with memory capacity and network delays. Moreover, a quantum error correction simulator is integrated for the first time in a cloud service platform, which can perform simulations of stabilizer circuits with of tens of thousands of qubits with a performance improvement of 5-15 times, compared with an open-sourced counterpart.

Huawei also showcased its quantum programming framework for the first time, which is compatible with the ProjectQ. The framework can significantly improve the performance of parallelized implementation of quantum algorithms. It also provides new features such as a user-friendly quantum circuit orchestration Graphical User Interface (GUI), and an innovative Block User Interface (BlockUI), allowing hybrid classical-quantum programming in an easy and intuitive way.

Dr. Man-Hong Yung, Huawei's Chief Quantum Computing Software and Algorithm Scientist, released the quantum computing simulation HiQ cloud service platform

"Quantum computation is a revolutionary technology that is different from classical computing," said Dr. Man-Hong Yung, Huawei's Chief Quantum Computing Software and Algorithm Scientist. "It is also a future-oriented core technology for cloud computing. Quantum algorithms provide a new perspective to AI algorithms, inspiring better classical AI algorithms and offering more powerful computing capability. Huawei has taken a critical step towards the research and innovation of quantum computing by releasing the HiQ cloud service platform, and will continue to invest in quantum computing in the future. Huawei’s HiQ will be fully open to the public, inviting developers, researchers, teachers, and students, to jointly innovate and promote technological research and industrialization of quantum computing."

Quantum computing represents an exciting computing technology for the future. For some computing tasks, it may take tens of thousands of years for classical computers, a quantum computer could complete the same task in just a few minutes, or even seconds. It can lead to a new revolution for artificial intelligence, new material design, drug development, complex optimization, and scheduling problems.

However, quantum computing has many technical challenges in terms of hardware, software, algorithms, and systems. Engineering such a complex system requires breakthroughs in hardware and control systems as well as software and algorithms.

Before the technologies of quantum computing hardware become mature, simulators of quantum computing in classical platform will play an important role in quantum circuit simulation and development and verification of quantum algorithm and software.

By releasing the quantum computing simulation cloud service platform — HiQ marks Huawei's first step in the research and innovation of quantum computing. Meanwhile, Huawei fully embraces the concept of win-win cooperation in quantum computing software. The development of HiQ would lead to technological breakthroughs in academia and promote industrial partners' research and industrialization in the field of quantum computing.

 

[Globenim]

When I hear "Cloud Service" uttered in 1st generation application my mind goes instantly "Nope".

 

[JSCh]

PUBLIC RELEASE: 30-OCT-2018
Tianhe-2 supercomputer works out the criterion for quantum supremacy
SCIENCE CHINA PRESS

​

(a) The Tianhe-2 supercomputer used for permanent calculation in simulating the boson sampling performance. (b) A small photonic chip could perform the same boson sampling task in the quantum computing protocol.
CREDIT: ©Science China Press

Quantum supremacy refers to the super strong calculation capacity of a quantum computer to surpass that of any classical computer. So far, such a quantum computer has not been physically made, but as with the rapid development of quantum technologies in recent years, the voice for pursuing the superiority by quantum computing is more loudly heard and how to quantitatively define the criteria of quantum supremacy becomes a key science question. Recently, a world's first criterion for quantum supremacy was issued, in a research jointly led by Prof. Junjie Wu in National University of Defense Technology and Prof. Xianmin Jin in Shanghai Jiao Tong University. They reported the time needed to calculate boson sampling, a typical task that quantum computers would excel at, in a most powerful classical supercomputer, and the paper was published in National Science Review.

Boson sampling, as introduced by one of the authors, is to sample the distribution of photons (bosons), and theoretically takes only polynomial time by quantum computers but exponential time by classical computers, showing quite evident quantum advantages as the number of photons involved in the boson sampling system increases. Besides, boson sampling, essentially an analog quantum computing protocol, maps the task directly in the photonic quantum system, and hence is much easier to implement than those based on universal quantum computing. Therefore, the task for boson sampling can be a very good candidate for defining quantum supremacy, for its preference to quantum computing over classical computing and its relative easier realization in the near future. Once a quantum computer can perform boson sampling task for a photon number larger and calculation time shorter than the best classical computer, the quantum supremacy is claimed to be achieved.

In the research led by Prof. Junjie Wu and Prof. Xianmin Jin, the boson sampling task was performed on Tianhe-2 supercomputer, which ever topped the world rank of supercomputers during 2013-2016, and still represents the tier one level of computing power that classical computers could ever achieve. The permanent calculation is a core part for theoretically performing boson sampling on a classical computer. If one just calculate the permanent directly based on its definition, it requires an algorithm with time complexity O(n!* n). The researchers used two improved algorithm, Ryser's algorithm and BB/FG's algorithm, both in the time complexity of O(n2* 2n). By performing matrix calculation on up to 312?000 CPU cores of Tianhe-2, they inferred that the boson sampling task for 50 photons requires 100 minutes using the then most efficient computer and algorithms. Put it in other words, if a physical quantum device could 50-photon boson sampling in less than 100 minutes, it achieves the quantum supremacy.

If such a quantum setup could be experimentally made, it quite likely will be very quick as photons travel in the speed of light, but many challenges still lie ahead for its experimental implementation. Prof. Xianmin Jin used to conduct pioneering research on boson sampling experiment in Oxford University. So far, the world record for the photon number in boson sampling experiment still remains no more than five. There's still a long way to go towards the ideal quantum supremacy.

An author for this Tianhe-2 project also pointed out that, as the limit for classical computing power would keep increasing with the improvement of supercomputers, and more efficient permanent calculation algorithms would emerge that require a time complexity less than O(n2* 2n), the time required for 50-photon boson sampling may be further reduced, making an even more stringent criterion for quantum supremacy. Meanwhile, a task to demonstrate quantum supremacy does not necessarily have any real applications. It is worthwhile to realize a wide range of useful applicable fields by quantum computing while carrying on the pursuit of quantum supremacy.


Tianhe-2 supercomputer works out the criterion for quantum supremacy | EurekAlert! Science News

Junjie Wu, Yong Liu, Baida Zhang, Xianmin Jin, Yang Wang, Huiquan Wang & Xuejun Yang. A benchmark test of boson sampling on Tianhe-2 supercomputer. National Science Review (2018); DOI: 10.1093/nsr/nwy079​

 

[JSCh]

Chinese scientists develop a photonic quantum chip for boosting analog quantum computing

(Xinhua) 10:20, May 12, 2018

WASHINGTON, May 11, (Xinhua) -- Chinese scientists demonstrated the first two-dimensional quantum walks of single photons in real spatial space, which may provide a powerful platform to boost analog quantum computing.

They reported in a paper published on Friday in the journal Science Advances a three-dimensional photonic chip with a scale up to 49-multiply-49 nodes, by using a technique called femtosecond direct writing.

Jin Xianmin, a quantum communication researcher with Shanghai Jiaotong University, who led the study, told Xinhua, it is the largest-scaled chip reported so far that allows for the realization of this two-dimensional quantum walk in real spatial space, and potential exploration for many new quantum computing tasks.

Jin and his colleague showed that the dimension and scale of quantum system could be employed as new resources for boosting the quantum computing power.

The researchers said, universal quantum computers came under the spotlight since last year, as IBM, Google, Intel and the rivals constantly competed to announce their new records on the achieved number of qubits.

However, universal quantum computers are far from being feasible before error correction and full connections between the increasing numbers of qubits could be realized.

In contrast, analog quantum computers, or quantum simulators, can be built in a straightforward way to solve practical problems directly without error correction, and potentially be able to beat the computational power of classical computers in the near future.

Quantum walk in a two-dimensional array is a strikingly powerful and straightforward approach to analog quantum computing. It maps certain computing tasks into the coupling matrix of the quantum paths, and provides efficient solutions to those even classically intractable problems.

Prominent quantum advantages will be promptly achievable as long as the scale of quantum systems goes above a considerably large level.

During the past two decades, a traditional and challenging method has been through increasing the photon number, which suffers from probabilistic generation of single photons and multiplicative loss, according to the researchers.

This ingenuous alternative way from increasing the external physics dimension and complexity of the quantum evolution system may accelerate future analog quantum computing, said Jin.

Letter | Published: 29 October 2018
Experimental quantum fast hitting on hexagonal graphs

• Hao Tang,
• Carlo Di Franco,
• Zi-Yu Shi,
• Tian-Shen He,
• Zhen Feng,
• Jun Gao,
• Ke Sun,
• Zhan-Ming Li,
• Zhi-Qiang Jiao,
• Tian-Yu Wang,
• M. S. Kim &
• Xian-Min Jin

Nature Photonics (2018) | Download Citation

Abstract

Quantum walks are powerful kernels in quantum computing protocols, and possess strong capabilities in speeding up various simulation and optimization tasks. One striking example is provided by quantum walkers evolving on glued trees1, which demonstrate faster hitting performances than classical random walks. However, their experimental implementation is challenging, as this involves highly complex arrangements of an exponentially increasing number of nodes. Here, we propose an alternative structure with a polynomially increasing number of nodes. We successfully map such graphs on quantum photonic chips using femtosecond-laser direct writing techniques in a geometrically scalable fashion. We experimentally demonstrate quantum fast hitting by implementing two-dimensional quantum walks on graphs with up to 160 nodes and a depth of eight layers, achieving a linear relationship between the optimal hitting time and the network depth. Our results open up a scalable path towards quantum speed-up in classically intractable complex problems.


Experimental quantum fast hitting on hexagonal graphs | Nature Photonics

 

[JSCh]

Quantum adiabatic and quantum circuit algorithms are equivalent, say physicists
20 Nov 2018 Hamish Johnston

​

Exactly equivalent: Quantum adiabatic and quantum circuit algorithms should take the same time to run (Courtesy: iStock/Devrimb)

Practical quantum computers could be one step closer thanks to physicists in China, who have published a rigorous proof that “quantum circuit” algorithms can be transformed into algorithms that can be executed at the same running time on adiabatic quantum computers .

A quantum circuit algorithm runs on a quantum computer made up of a sequence of quantum-logic gates. This set-up resembles a conventional computer, which runs algorithms on sequences of classical logic gates. However, fundamental differences between quantum and classical computation mean that certain problems can be solved much more quickly on a quantum computer.

A big challenge for researchers trying to create practical quantum computers is decoherence – the degradation of quantum information caused by interactions with the surrounding environment. This makes it very hard to maintain the quantum nature of information as it is being processed, which is why only very basic quantum computations have been possible so far.

Ground-state solution
Adiabatic quantum computers take a different approach by using a network of quantum nodes (such as superconducting circuits) that can be configured to represent a complicated computational problem. The solution to the problem is given by the lowest energy – or ground – state of the system, which can be very complicated to determine.

The trick is to first configure the system so that it has a much simpler ground state and then transform it into the much more complicated system representing the solution. If the transformation is done adiabatically, which means there is minimal transfer of energy into or out of the system, then the system will remain in its ground state during the transformation – thus revealing the solution to the problem. Because the system is in its ground state throughout the process, decoherence may not be as much of a problem as it is in systems running quantum circuit algorithms.

Algorithms for adiabatic quantum computers were first proposed in 2000 and since then, researchers have shown that quantum adiabatic algorithms and quantum circuit algorithms are “polynomially equivalent”. This means that if one type of algorithm takes time t to solve a problem, then the other will take a polynomial value of t to the nth power to complete the task.

Rigorous proof
Now, Biao Wu and colleagues at Peking University have shown that the two types of algorithm are even more similar by publishing a “rigorous proof that quantum circuit algorithm can be transformed into quantum adiabatic algorithm”. This means that if one type of algorithm takes time t to solve a problem, then the other will take t multiplied by a constant.

Wu told Physics World that the result is good news for people trying to build adiabatic quantum computers: “In principle, any quantum-computing problem can be solved using a quantum adiabatic algorithm as efficiently as using quantum circuit algorithm.

The proof is described in Chinese Physics Letters.



Quantum adiabatic and quantum circuit algorithms are equivalent, say physicists – Physics World

Hongye Yu, Yuliang Huang, Biao Wu. Exact Equivalence between Quantum Adiabatic Algorithm and Quantum Circuit Algorithm. Chinese Physics Letters, October 2018. DOI: 10.1088/0256-307x/35/11/110303​

 

[JSCh]

Quantum computer control system launched in east China
Source: Xinhua| 2018-12-11 15:31:40|Editor: Liangyu


HEFEI, Dec. 11 (Xinhua) -- China's first quantum computer control system with independent intellectual property rights has been launched in Hefei, capital of eastern province of Anhui, according to sources with the city's high-tech zone on Tuesday.

The control system was developed by Origin Quantum Computing Technology Co. Ltd., a startup which develops and commercializes quantum computers.

The essential role of the control system is to provide the precise signal needed for the operation of quantum chips. It can also process feedback information and compile computer programs, according to the company.

"The control system is an indispensable part of quantum computers because it enables the quantum chip to play out its maximum performance," said Guo Guangcan, a renowned expert in quantum information.

It can be applied to various fields such as testing of quantum chips and the theory building of quantum computers, and provide solutions for a wide range of scientific experimental researches including precision measurement and basic science research.

 

[TaiShang]

Quantum computer control system launched in east China
Xinhua, December 11, 2018

China's first quantum computer control system with independent intellectual property rights has been launched in Hefei, capital of eastern province of Anhui, according to sources with the city's high-tech zone on Tuesday.

The control system was developed by Origin Quantum Computing Technology Co. Ltd., a startup which develops and commercializes quantum computers.

The essential role of the control system is to provide the precise signal needed for the operation of quantum chips. It can also process feedback information and compile computer programs, according to the company.

"The control system is an indispensable part of quantum computers because it enables the quantum chip to play out its maximum performance," said Guo Guangcan, a renowned expert in quantum information.

It can be applied to various fields such as testing of quantum chips and the theory building of quantum computers, and provide solutions for a wide range of scientific experimental researches including precision measurement and basic science research.

http://www.china.org.cn/business/2018-12/11/content_74263740.htm

 

[JSCh]

Letter | Published: 29 October 2018
Experimental quantum fast hitting on hexagonal graphs

• Hao Tang,
• Carlo Di Franco,
• Zi-Yu Shi,
• Tian-Shen He,
• Zhen Feng,
• Jun Gao,
• Ke Sun,
• Zhan-Ming Li,
• Zhi-Qiang Jiao,
• Tian-Yu Wang,
• M. S. Kim &
• Xian-Min Jin

Nature Photonics (2018) | Download Citation

Abstract

Quantum walks are powerful kernels in quantum computing protocols, and possess strong capabilities in speeding up various simulation and optimization tasks. One striking example is provided by quantum walkers evolving on glued trees1, which demonstrate faster hitting performances than classical random walks. However, their experimental implementation is challenging, as this involves highly complex arrangements of an exponentially increasing number of nodes. Here, we propose an alternative structure with a polynomially increasing number of nodes. We successfully map such graphs on quantum photonic chips using femtosecond-laser direct writing techniques in a geometrically scalable fashion. We experimentally demonstrate quantum fast hitting by implementing two-dimensional quantum walks on graphs with up to 160 nodes and a depth of eight layers, achieving a linear relationship between the optimal hitting time and the network depth. Our results open up a scalable path towards quantum speed-up in classically intractable complex problems.


Experimental quantum fast hitting on hexagonal graphs | Nature Photonics

A First: 3D-Chip-Based Analog Photonic Quantum Computer Demonstrates Quantum Fast Hitting
Synced
Nov 12

Press Release provided by
Xianmin Jin Research Team, Shanghai Jiao Tong University

Analog quantum computing has been an appealing tool with potential real-life applications on various optimization and simulation tasks, and much less stringent requirements on error corrections compared to universal quantum computing. Quantum walks, a key protocol for analog quantum computing, has theoretically shown many quantum advantages — for example in the speedup of fast hitting tasks in glued tree structures. However, in order to bring the advantages into reality, there exist many prerequisites on the physics quantum system. One is to make the system scalable so that it can cope with real problems of certain complexity.

The demonstration of analog quantum computing has normally been on a very small scale for proof-of-principle studies, and the number of photons is the main resource for expanding the quantum system. Until very recently, as Nature Photonics reported, a scalable analog quantum computing device was realized on an integrated quantum photonic chip, which opened a new roadmap for using the dimension and scale of the quantum evolution system as the new resource for analog quantum computing.

Schematic diagram of scalable analog quantum computing device for fast hitting tasks on hexagonal graphs.

In research conducted by Prof. Xian-Min Jin and his team in Shanghai Jiao Tong University, collaborating with Prof. Myungshik Kim in Imperial College London and Dr. Carlo Di Franco in Nanyang Technological University, hexagonal graphs as an alternative structure was proposed for fast hitting tasks instead of the traditional binary glued trees. The hexagonal graphs resemble the gluing of two tree-like structures, and are highly scalable to be mapped in the three-dimensional integrated quantum photonic chips, where the longitudinal direction represents the evolution time, and the cross-section view shows the hexagonal structure formed by waveguide arrays. The team led by Xian-Min Jin drew on their experimental expertise to report the largest-scale integrated photonic chip to demonstrate the first quantum walk experiment in real two-dimensional space.

For the research on quantum fast hitting, they injected photons from the “Entry” waveguide and measured the light intensity at the “Exit” waveguide as the “hitting efficiency.” Researchers found that quantum walks perform quadratically faster than classical random walks, showing the first experimental demonstration of quantum advantages in fast hitting tasks.

Schematic diagram mapping the hexagonal graphs for fast hitting onto the photonic chip.

A comparison of classical fast hitting and quantum fast hitting.

Experimental patterns showing the optimal quantum fast hitting on hexagonal graphs of different layer depths. In these graphs of different complexities, quantum fast hitting always has high light intensity in the “Exit” (the right-most waveguide).

The experimental implementation for fast hitting on glued trees represents exciting progress, as it realizes one of the most representative examples that quantum theoreticians have raised to showcase the speedup by quantum walks. Besides, considering the protocol’s essence as an optimization process and the similarity between binary trees and decision trees in computer science, the protocol of fast hitting on glued trees may further trigger many useful applications that utilize quantum speed-up for tasks such as logistics, finance and information searching. “Our demonstration can also be seen as a first step towards the realization of scalable quantum fast search. By adding more photons we can also build a large network of nonclassical states which can be used for applications as well as fundamental studies.” said Prof. Myungshik Kim.

The scalable quantum device enabled by the integrated quantum photonic chip also provides an excellent platform for quantum simulation of other physical systems, and may potentially stimulate research on many multidisciplinary topics and emerging scientific questions, including astronomy simulation, quantum machine learning, quantum topological photonics, quantum imaging for biological and medical applications, and so on.

This October the team led by Prof. Xian-Min Jin launched the first software for photonic analog quantum computing, FeynmanPAQS, with the aim of encouraging wider participation and brainstorming for various simulation proposals and potential applications connecting real problems. It would be delightful in the near future to see more quantum benefits being brought into reality.

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