Chinese Scientists Make Breakthrough in Quantum Computing

[JSCh]

Quantum computer prospects improve on the surface
24 Apr 2019 Bence Börcsök

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C. Chen (left), T. Zhang (middle) and T. Z. Zhang (right) working on the refrigerated scanning tunnelling microscope. Credit: T. Zhang

There is a huge race to develop quantum computers for their enormous potential applications. Theory predicts that they can perform certain algorithms, such as factoring numbers or search algorithms, much faster than classical computers. Quantum computers would not only revolutionize informatics but would impact many areas of life, for example economics and communication, as well. Now a team of scientists at Fudan University led by Donglai Feng and Tong Zhang, in collaboration with the group of Zhongxian Zhao and Xiaoli Dong at the Institute of Physics of the Chinese Academy of Sciences, have made a big step towards quantum computers. For the first time they have measured the theoretically predicted value for the conductance of Majorana zero modes (MZM) – potential building blocks of a quantum computer – inside the cores of the vortices formed by a superconductor’s current.


--> Quantum computer prospects improve on the surface - Physics World

 

[JSCh]

A device for generating entangled photons includes concentric rings made of an aluminium-gallium-arsenide compound encircling a nanometre-scale semiconductor. Credit: Jin Liu

OPTICS AND PHOTONICS | 26 APRIL 2019
Tiny device cranks out quantum communication’s raw materials
Quantum dots help to make entangled photons with high efficiency.

Scientists have at last succeeded in creating a reliable stream of entangled photons — an advance that could boost quantum technologies.

Quantum-communication networks and quantum computers require ‘entangled’ photons, pairs of intrinsically linked light particles that can carry ultra-secure signals and help to process quantum computations. But these fragile photon pairs are tricky to manufacture, and for years researchers have sought a reliable method for producing a high-quality stream of them.

Xuehua Wang of Sun Yat-sen University in Guangzhou, China, and his colleagues enclosed a nanometre-scale semiconductor called a quantum dot in concentric rings made of an aluminium-gallium-arsenide compound. When the researchers shone a laser on the dot, it emitted entangled photons that were reflected multiple times by the rings and eventually guided to a lens that efficiently harvested the photons, amplifying the detected quantum signal.

This photon source, which could be easily integrated into a computer chip, produces a bright and steady flow of indistinguishable photons. A reliable supply of such photons will be crucial for relaying quantum signals over long distances and for building high-performing quantum computers.

Nature Nanotechnol. (2019)​

Tiny device cranks out quantum communication’s raw materials : Research Highlights | Nature

 

[JSCh]

Strongly correlated quantum walks with a 12-qubit superconducting processor
Published in Science, May 2019
DOI: 10.1126/science.aaw1611

Authors

Zhiguang Yan, Yu-Ran Zhang, Ming Gong, Yulin Wu, Yarui Zheng, Shaowei Li, Can Wang, Futian Liang, Jin Lin, Yu Xu, Cheng Guo, Lihua Sun, Cheng-Zhi Peng, Keyu Xia, Hui Deng, Hao Rong, J. Q. You, Franco Nori, Heng Fan, Xiaobo Zhu, Jian-Wei Pan​

Abstract

Quantum walks are the quantum analogs of classical random walks, which allow simulating large-scale quantum many-body systems and realizing universal quantum computation without time-dependent control. We experimentally demonstrate quantum walks of one and two strongly correlated microwave photons in a 1D array of 12 superconducting qubits with short-range interactions. First, in one-photon quantum walks, we observed the propagation of the density and correlation of the quasi-particle excitation of the superconducting qubit, and quantum entanglement between qubit pairs. Second, when implementing two-photon quantum walks by exciting two superconducting qubits, we observed the fermionization of strongly interacting photons from the measured time-dependent long-range anticorrelations, representing the antibunching of photons with attractive interactions. The demonstration of quantum walks on a quantum processor, using superconducting qubits as artificial atoms and tomographic readout, paves the way to quantum simulation of many-body phenomena and universal quantum computation.

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Strongly correlated quantum walks with a 12-qubit superconducting processor | Science

 

[GumNaam]

^^^ mit's reaction...

 

[JSCh]

Article | OPEN | Published: 01 May 2019
Generation of multiphoton quantum states on silicon
Ming Zhang, Lan-Tian Feng, Zhi-Yuan Zhou, Yang Chen, Hao Wu, Ming Li, Shi-Ming Gao, Guo-Ping Guo, Guang-Can Guo, Dao-Xin Dai & Xi-Feng Ren.

Light: Science & Applications volume 8, Article number: 41 (2019)

Editorial Summary

Photonics: Pairing-up for next generation photonic quantum technologies

Chinese scientists have developed a technique for generating photon-pairs for use in quantum devices, paving the way for a range of new photonic quantum technologies. Multi-photon quantum sources are critical for the development of new photonic quantum technologies, and drove Dao-Xin Dai and colleagues from Zhejiang University, in collaboration with researchers from the University of Science and Technology of China, to develop a technique that generates high-quality photonic quantum states. Using a method called spontaneous four-wave mixing, whereby three electromagnetic fields interact to produce a fourth field, the team created multi-photon quantum states in a silicon nanophotonic spiral waveguide. The technique produces bright, tunable, stable and scalable multi-photon quantum states, and is compatible with a current fiber and integrated circuit manufacturing processes, opening the door to new photonic quantum technologies in communications, computation, and imaging.
​

Abstract

Multiphoton quantum states play a critical role in emerging quantum technologies and greatly improve our fundamental understanding of the quantum world. Integrated photonics is well recognized as an attractive technology offering great promise for the generation of photonic quantum states with high-brightness, tunability, stability, and scalability. Herein, we demonstrate the generation of multiphoton quantum states using a single-silicon nanophotonic waveguide. The detected four-photon rate reaches 0.34 Hz even with a low-pump power of 600 μW. This multiphoton quantum state is also qualified with multiphoton quantum interference, as well as quantum state tomography. For the generated four-photon states, the quantum interference visibilities are greater than 95%, and the fidelity is 0.78 ± 0.02. Furthermore, such a multiphoton quantum source is fully compatible with the on-chip processes of quantum manipulation, as well as quantum detection, which is helpful for the realization of large-scale quantum photonic integrated circuits (QPICs) and shows great potential for research in the area of multiphoton quantum science.​

Generation of multiphoton quantum states on silicon | Light: Science & Applications

 

[JSCh]

Propagation and Localization of Collective Excitations on a 24-Qubit Superconducting Processor
Yangsen Ye, Zi-Yong Ge, Yulin Wu, Shiyu Wang, Ming Gong, Yu-Ran Zhang, Qingling Zhu, Rui Yang, Shaowei Li, Futian Liang, Jin Lin, Yu Xu, Cheng Guo, Lihua Sun, Chen Cheng, Nvsen Ma, Zi Yang Meng, Hui Deng, Hao Rong, Chao-Yang Lu, Cheng-Zhi Peng, Heng Fan, Xiaobo Zhu, and Jian-Wei Pan

Phys. Rev. Lett. 123, 050502 – Published 30 July 2019

ABSTRACT
Superconducting circuits have emerged as a powerful platform of quantum simulation, especially for emulating the dynamics of quantum many-body systems, because of their tunable interaction, long coherence time, and high-precision control. Here in experiments, we construct a Bose-Hubbard ladder with a ladder array of 20 qubits on a 24-qubit superconducting processor. We investigate theoretically and demonstrate experimentally the dynamics of single- and double-excitation states with distinct behaviors, indicating the uniqueness of the Bose-Hubbard ladder. We observe the linear propagation of photons in the single-excitation case, satisfying the Lieb-Robinson bounds. The double-excitation state, initially placed at the edge, localizes; while placed in the bulk, it splits into two single-excitation modes spreading linearly toward two boundaries, respectively. Remarkably, these phenomena, studied both theoretically and numerically as unique properties of the Bose-Hubbard ladder, are represented coherently by pairs of controllable qubits in experiments. Our results show that collective excitations, as a single mode, are not free. This work paves the way to simulation of exotic logic particles by subtly encoding physical qubits and exploration of rich physics by superconducting circuits.​

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Received 7 May 2019

DOI: https://doi.org/10.1103/PhysRevLett.123.050502

© 2019 American Physical Society


Phys. Rev. Lett. 123, 050502 (2019) - Propagation and Localization of Collective Excitations on a 24-Qubit Superconducting Processor

​

 

[Menthol]

When the final product appear in the market for consumer use?

Despite it's just having several cubits?

When the final product appear in the market for consumer use?

Despite it's just having several cubits?

 

[JSCh]

Prof. Kihwan Kim’s group published work in Nature, experimentally demonstrating the global gates up to 4-qubits

Professor Kihwan Kim’s group in the Center of Quantum Information (CQI), Institute of Interdisciplinary Information (IIIS), Tsinghua University, has recently proposed and successfully demonstrated powerful more than two-qubit quantum gate operations in a trapped ion system. The work “Quantum Simulation of the Quantum Rabi Model in a Trapped Ion” was published on July 24 in Nature. The corresponding authors of the paper are Yao Lu, PhD candidate of IIIS, and Prof.Kihwan Kim, associate professor of IIIS. The equally contributed first authors of the work are Yao Lu, Shuaining Zhang and Kuan Zhang, Ph.D. candidates of IIIS.

Figure 1 Usefulness of global entangling gate

Nowadays there has been a lot of progress in developing quantum system for quantum computation or quantum simulation so that quantum computers are getting closer to reality. It is the time to find out and fill missing technologies for the practical quantum computation. In principle, the universal quantum computation can be decomposed by single qubit and two-qubit entangling gates, but surely such decomposition is not generally efficient and has exponential overheads in the operation. The development of more efficient multiple qubits, more than two-qubit gates, would be essential for a practical quantum computation. Many theoretical papers have pointed out the usefulness and necessity of such multi-qubit gates. However, no scalable realization of more than two-qubit gate has been demonstrated experimentally.

Figure 2 Ion trap that contains multiple ions for the quantum computation

In this letter, prof. Kim’s group reported the realization of scalable, more than two-qubit gates in a trapped ion system. Trapped ion system is one of the strong leading candidates for the implementation of practical quantum computers. Recently a blue-print of a trapped ion system scalable up to a few dozens of qubits in a single trap has been proposed and a small programmable quantum computer has been realized following the blue-print. Until now, all the operations in such scalable trapped ion system are based on single qubit and two-qubit gates. The research grouped develop the novel scheme of more than two-qubit gates and experimentally demonstrate the global gates up to 4-qubits as an example. They benchmarked the performance of the operation by observing the fidelity of Bell-state, which is significantly larger than classical bounds.

Figure 3 Experimental realization of the global entangling gates

This experiment was completed by Yao Lu, Shuaining Zhang, and Dr. Wentao Chen, Yangchao Shen, and Jialiang Zhang supported the experiment. Jingning Zhang, Assistant Researcher of IIIS, provided theoretical support for this experiment. This work was supported by the National Key Research and Development Program of China under Grants No. 2016YFA0301900 and No. 2016YFA0301901 and the National Natural Science Foundation of China Grants No. 11574002, and No. 11504197, the National Natural Science Foundation of China.

The paper is available at: https://www.nature.com/articles/s41586-019-1428-4

Source: Institute of Interdisciplinary Information
Editor: Guo Lili


https://news.tsinghua.edu.cn/publis...055110632290290/20190803055110632290290_.html

Yao Lu, Shuaining Zhang, Kuan Zhang, Wentao Chen, Yangchao Shen, Jialiang Zhang, Jing-Ning Zhang, Kihwan Kim. Global entangling gates on arbitrary ion qubits. Nature (2019). DOI: 10.1038/s41586-019-1428-4​

 

[JSCh]

A perfect single-photon source for quantum computing, finally
This is a fundamental key step for optical quantum computing, which promises a huge increase of computational power compared to our conventional computers.

2 days ago by University of Science and Technology of China

An international multi-institute collaboration, led by Professor Chao-Yang Lu and Jian-Wei Pan from the University of Science and Technology of China, has demonstrated a semiconductor-based source of single photons that for the first simultaneously fulfills all the demanding requirements of quantum computing. This is a fundamental key step for optical quantum computing, which promises a huge increase of computational power compared to our conventional computers.

A central theme of ongoing experimental endeavor for the near-term goal of “quantum supremacy” and the long-term goal of scalable quantum computing is to increase both the quantity and the quality of quantum bits in various physical systems. In optical quantum computing, where single photons serve as elementary qubits, their quantity and quality are associated with the efficiency and indistinguishability of the single-photon source. The realization of an optimal single-photon source with simultaneously near-unity system efficiency and indistinguishability is the biggest challenge for the field.

The semiconductor single-photon device. Size: 10 microns height. Credit: Si Chen

Despite tremendous efforts in the past 20 years, the experimentally generated single-photon sources still fell short of the minimal required efficiency of 50% for quantum computational supremacy. This limitation is due to two fundamental problems. One is that the bright quantum-dot excitonic transition is two-fold degenerate with random left and right circular polarization. The other one is associated with the resonant excitation. However, to select only one polarization, and to suppress the laser scattering, the cross-polarization extinction sacrificed at least 50% of the single photons. Overcoming the outstanding challenge of 50% efficiency loss has remained the most difficult and final challenge for an ultimate high-performance single-photon source, both theoretically and technologically.

The team led by Prof. Lu and Pan put forward a feasible proposal that kills the two birds with one stone and report its experimental demonstrations. The trick is to use an elliptical cavity that breaks the original polarization symmetry of the quantum dot emission. Moreover, they develop a new way for background-free resonance fluorescence without sacrificing the system efficiency. The generality and versatility of the protocol have been demonstrated in both narrowband and broadband cavities. The combination of the new theory and experiment created the brightest sources of single indistinguishable photons to date in all physical systems.

Arrays of single-photon devices in elliptical bulls-eye structure. Size: 1 micron diameter each. Credit: Hai Hu

Because single-photon source is the most fundamental, and also the most challenging part for optical quantum computing, it will enable wide new applications, for example:

• Quantum computing: High-efficiency boson sampling, an intermediate quantum computing algorithm that promises to demonstrate the quantum supremacy, a computational speedup compared to classical computers.
• Quantum communications: Increase the distance and the key rate of quantum cryptography
• Quantum metrology: Reformulate the candela definition in terms of photon number rather than in optical power.

Artists’ impression of an array of Bragg grating cavity on the top of the sample substrate. Credit: Li-Chao Peng



A perfect single-photon source for quantum computing, finally | SciGlow

Hui Wang, Yu-Ming He, T.-H. Chung, Hai Hu, Ying Yu, Si Chen, Xing Ding, M.-C. Chen, Jian Qin, Xiaoxia Yang, Run-Ze Liu, Z.-C. Duan, J.-P. Li, S. Gerhardt, K. Winkler, J. Jurkat, Lin-Jun Wang, Niels Gregersen, Yong-Heng Huo, Qing Dai, Siyuan Yu, Sven Höfling, Chao-Yang Lu & Jian-Wei Pan. Towards optimal single-photon sources from polarized microcavities. Nature Photonics (2019). DOI: 10.1038/s41566-019-0494-3​

 

[JSCh]

Leading role in quantum field could await China
By Zhu Lixin in Hefei, Anhui Province | China Daily Global | Updated: 2019-08-08 09:44

Composite photo taken on Dec 9, 2016 shows a satellite-to-earth link established between quantum satellite "Micius" and the quantum teleportation experiment platform in Ali, Southwest China's Tibet autonomous region. [Photo/Xinhua]

Pan Jianwei, a leading Chinese scientist who has been at the center of China's efforts to reach quantum supremacy since 2001, said the country was once "only a follower "in modern information science.

But thanks to hard work and breakthroughs, China now has "a chance to be a leader", Pan, 48, a leading quantum information scientist and a member of the Chinese Academy of Sciences, remarked in a profile published in MIT Technology Review.

Pan, a member of the Chinese Academy of Sciences, began putting together a quantum information research team in 2001 at the University of Science and Technology of China in Hefei, Anhui province.

Quantum mechanics is defined as the body of scientific laws regarding nature at the smallest scales - the energy levels of atoms and subatomic particles.

During the Mozi Forum, an academic forum this spring in Hefei, Pan spoke about breakthroughs in the field. These included the revelation that his team plans to build a prototype quantum computer no larger than a laptop, but whose computing capability could surpass the world's most powerful supercomputer in three to five years.

President Xi Jinping said during an inspection visit to Hefei in April 2016 that Pan's field of study held much promise and was of great importance.

At the Hefei university's Institute of Advanced Technology, where the control center is based for the 2,000-kilometer Beijing-Shanghai quantum communication trunk line, Xi said China must strengthen its own innovation capability while continuing to open up.

The quantum communication-trunk line began operating in 2016, shortly after China's - and the world's - first satellite for quantum experiments was launched.

Pan led the design and construction efforts of both the trunk line and the satellite.

At the recent academic forum, Pan talked about the challenges and breakthroughs in the satellite and quantum computer projects.

"We have already conducted successful experiments of quantum communication between Beijing and Vienna, and are now cooperating with scientists from Italy, Singapore, Germany, Russia and Sweden with our satellite," Pan said.

"At first, the quantum experiential satellite had a problem - it would only work at night. But so far we have solved it well, enabling it to work throughout the day.

"The breakthrough," he added, "has laid the foundation for building a network of more satellites in the future."

Pan also noted that his team revealed a prototype quantum computer in 2017 that could manipulate 10 quantum bits, or qubits, for data storage and calculations.

Last year, the team increased the capacity to 18 qubits. When the capacity reaches between 20 and 30 qubits, the computer's calculation capacity could match a popular commercial laptop - a goal that will be reached soon, Pan said.

"We aim to raise the number to 40 to 50 in three to five years. Then the calculation capacity will surpass any one of the world's most powerful supercomputers, while its size will be no larger than a laptop," Pan said at the forum.

Conventional computers can only store data in 1 or 0 binary bits. Qubits, on the other hand, are subatomic particles that can be both 1 and 0 at the same time, holding exponentially more information.

Pan's 34-member team of physicists has published at least eight papers in the leading science journals Nature and Science in the past three years, according to USTC.

Pan, in an interview during this year's two sessions, the annual meetings of China's top legislative and political advisory bodies, said: "Challenges remain for future development in the field, considering the increasingly fierce competition in the world. Further breakthroughs will require more interdisciplinary collaboration."

He has proposed building a national laboratory in the Hefei National High-Tech Industry Development Zone for quantum information science and technology. Construction of a lab has nearly been completed on a 330-hectare area in the Hefei zone.

"Applying new technology and perfecting it in experiments will at last result in new perspectives for fundamental scientific research," Pan told the forum in Hefei.

 

[JSCh]

Synopsis: Entangling the Radial Parts of Photons
August 8, 2019

Correlations between the radial position and radial momentum of entangled photons demonstrate the suitability of these properties for quantum information applications.

L. Chen/Xiamen University​

Photons have been entangled through most of their obvious physical properties, such as polarization, position and momentum, and even angular momentum. Now, Lixiang Chen, at Xiamen University, China, and colleagues demonstrate entanglement via two new properties of photons with a specific cross-sectional structure. The researchers produced pairs of entangled photons with well-defined “radial position” and “radial momentum,” meaning each photon’s wave function is localized at a certain radius and moves radially inwards or outwards with a certain momentum. Measurements made at a pair of detectors showed that the positions and momenta of the photons were correlated. The observations indicate that a photon’s radial components may be useful for various applications, such as quantum cryptography and optical micromanipulation.

The researchers fired a laser into a crystal, producing pairs of entangled structured photons with a method known as spontaneous parametric down-conversion. The photons in each pair were separated and sent into spatial light modulators (SLMs) along different arms of the experiment. The SLMs could function either as ring-shaped apertures (admitting only photons with a certain radial position) or diffraction gratings (transmitting only photons with a specific radial momentum). Using single-photon counters at the ends of the arms, the researchers demonstrated a degree of correlation between the two photons that could only be explained if the photons’ radial position and radial momentum were both entangled.

The researchers say that a photon’s radial properties could be harnessed with other entangled variables to improve the security of certain quantum communication schemes. Their method of selecting photons with a certain radial momentum might also be used to direct particles held by optical tweezers.

This research is published in Physical Review Letters.

–Marric Stephens
Marric Stephens is a freelance science writer based in Bristol, UK.


Physics - Synopsis: Entangling the Radial Parts of Photons

Realization of the Einstein-Podolsky-Rosen Paradox Using Radial Position and Radial Momentum Variables
Lixiang Chen, Tianlong Ma, Xiaodong Qiu, Dongkai Zhang, Wuhong Zhang, and Robert W. Boyd
Phys. Rev. Lett. 123, 060403 (2019)

Published August 8, 2019​

 

[JSCh]

Physicists set new record with entanglement of atomic Schrödinger cat states of up to 20 superconducting qubits
2019-08-10 Global Communications

Physicists have experimentally demonstrated quantum entanglement with 20 qubits on a superconducting circuit, surpassing the previous record of 12 entangled superconducting qubits.

Lead researcher WANG Haohua and co-workers at Zhejiang University, the CAS Institute of Physics, the CAS Institute of Automation and Beijing Computational Science Research Center, have published a paper on their work in a recent issue of Science.

Superconducting quantum processor with false-color circuit image showing 20 qubits (line shapes in cyan labeled clockwise from 1 to 20) interconnected by a central bus resonator B (gray).

Regular computers are based on “bits” as little switches pointing to either a 1 or a 0, to represent information. However, quantum computing relies on qubits, which can also represent a 0 or a 1. The crazy thing is that qubits can also achieve a mixed state, called a “superposition” where they are both 1 and 0 at the same time. This ambiguity—the ability to both “be” and “not be”—is key to the power of quantum computing.

The number of qubits is one of the key indicators for the performance of quantum computers. It is surmised that once the number of qubits adds up to 50, a quantum computer can surpass a supercomputer in computing while tackling specific problems. “Our chip is marked by its remarkable ability to interconnect all qubits, thereby promoting its working efficiency. This can account for the ground breaking entanglement of 20 qubits,” says one of the researchers.

By engineering a one-axis twisting Hamiltonian, the system of qubits, once initialized,coherently evolves to multicomponent atomic Schrödinger cat states, that is, superpositions of atomic coherent states including the GHZ state, within merely 187 ns. This is the hallmark of the ability to entangle these qubits.

Multicomponent atomic Schrödinger cat states of 20 qubits generated during the dynamics at Δ/2π ≈ –450 MHz

Multipartite entangled states are crucial for numerous applications in quantum information science. However, the generation and verification of multipartite entanglement on fully controllable and scalable quantum platforms poses an immense challenge. With a view to building qubit-qubit couplings, thus achieving multipartite entanglement, researchers delivered this 20-qubit superconducting quantum processor.

With all-to-all connectivity and programmable qubit-qubit couplings, this 20-qubit superconducting quantum processor represents a step toward realizing large-scale quantum computing. It also demonstrates the potential of an all-to-all connected circuit architecture for exploring profound quantum many-body physics, and also for applications in practical quantum metrology and quantum information processing.


Physicists set new record with entanglement of atomic Schrödinger cat states of up to 20 superconducting qubits | Zhejiang University

Chao Song, Kai Xu, Hekang Li, Yu-Ran Zhang, Xu Zhang, Wuxin Liu, Qiujiang Guo, Zhen Wang, Wenhui Ren, Jie Hao, Hui Feng, Heng Fan, Dongning Zheng, Da-Wei Wang, H. Wang, Shi-Yao Zhu. Generation of multicomponent atomic Schrödinger cat states of up to 20 qubits. Science (2019). DOI: 10.1126/science.aay0600​

 

[JSCh]

Synopsis: Toward Topological Protection with Qubits
August 20, 2019

A chain of superconducting qubits reproduces two key features of topological insulators.

W. Cai et al., Phys. Rev. Lett. (2019)

Reliable quantum computation will require devices that can protect fragile quantum states from environmental disturbances. To that end, some researchers have pinned their hopes on topological insulators, materials that intrinsically protect their novel electrical behavior in the face of external perturbations. However, no one has yet engineered a topological insulator in an ensemble of qubits, the quantum equivalent of digital bits. Now, Luyan Sun of Tsinghua University in Beijing and collaborators have done just that by crafting a string of qubits in which topological protection can be switched on and off at will.

The team fabricated a chain of qubits out of superconducting circuits. In the device’s default state, a spin-excitation (magnon) generated in one qubit would propagate back and forth along the chain. By tuning local magnetic fluxes to adjust the relative coupling strength between the qubits, however, the team engineered a topological magnon insulator that sustained the excitation and constrained it to a single qubit.

By observing the magnon dynamics over time, the team was able to characterize two hallmarks of any topological insulator: the winding number, which is a parameter in momentum space that does not change if the system is deformed, and edge states, in which qubit excitations crowd together at the boundaries of the system. Each has been seen before in other quibit systems but never simultaneously. The team says that these results show that superconducting qubit chains can not only be easily engineered to have topological protection but can also provide a flexible platform for investigating a variety of topological behaviors.

This research is published in Physical Review Letters.

–Christopher Crockett
Christopher Crockett is a freelance writer based in Arlington, Virginia.


Physics - Synopsis: Toward Topological Protection with Qubits

Observation of Topological Magnon Insulator States in a Superconducting Circuit
W. Cai, J. Han, Feng Mei, Y. Xu, Y. Ma, X. Li, H. Wang, Y. P. Song, Zheng-Yuan Xue, Zhang-qi Yin, Suotang Jia, and Luyan Sun

Phys. Rev. Lett. 123, 080501 (2019)
Published August 20, 2019​

 

[JSCh]

Viewpoint: Directly Measuring an Entangled State

• David J. Starling, Division of Science, Pennsylvania State University, Hazleton, PA 18202, USA

October 9, 2019• Physics 12, 110

Researchers have directly measured the components of a nonlocal, entangled wave function, rather than relying on indirect tomographic or reconstructive techniques.

​

APS/Alan Stonebraker​

Figure 1: Researchers have directly measured the wave function of two entangled photons. The experiment generates photon pairs, which travel down four separate paths (shown in blue). The photons are entangled in such a way that measuring which paths are taken can produce a set of "modular values," which reveal the nonlocal polarization state of the photons.

Measuring the quantum state of a system is difficult. The common way, called tomography, involves measuring multiple copies of the system and using the statistics of that ensemble to algorithmically guess the closest possible quantum state [1]. A more direct method exists using so-called weak values, which are the result of weak (low-precision) measurements on a pre- and postselected quantum state [2–4]. However, the weak value approach is limited when it comes to measuring nonlocal (spatially separated) quantum states. In a new work, the group of Guang-Can Guo at the University of Science and Technology of China has shown that it is possible to directly measure the wave function of two spatially separated entangled photons [5]. Rather than weak values, the researchers employ modular values, which are characterizations of a quantum system obtained by making a strong measurement of a qubit, called the meter, that is coupled to the system [6]. This demonstration may lead to more efficient methods for probing large entangled systems, as are imagined in future quantum information technologies.



...

Physics - Viewpoint: Directly Measuring an Entangled State

Direct Measurement of a Nonlocal Entangled Quantum State
Wei-Wei Pan, Xiao-Ye Xu, Yaron Kedem, Qin-Qin Wang, Zhe Chen, Munsif Jan, Kai Sun, Jin-Shi Xu, Yong-Jian Han, Chuan-Feng Li, and Guang-Can Guo

Phys. Rev. Lett. 123, 150402 (2019)

Published October 9, 2019​

 

[JSCh]

China's First Quantum Computer Prototype With IP Rights to Be Ready Next Year
CHEN YIZHAO
DATE : OCT 24 2019/SOURCE : YICAI

China's First Quantum Computer Prototype With IP Rights to Be Ready Next Year​

(Yicai Global) Oct. 24 -- Chinese startup Origin Quantum Computing Technology plans to launch China's first independently developed quantum computer prototype by the end of next year.

Origin Quantum's machine with a 6-qubit chip put online will have full intellectual property rights and the firm has applied for more than 200 patents and trademarks in the field, Guo Guoping, founder of the Hefei province-based company told Yicai Global in an interview.

Countries such as the US and Germany, as well as global tech giants, including Google and IBM, are working on building quantum computers, super-powerful machines that can crunch numbers in ways that normal computers can't.

The team of Origin Quantum, founded in 2017, stems from computer science and physics Ph.D. programs provided by Hefei's University of Science and Technology of China. The company's business involves applying quantum computing to chips, software, measurement and control, as well as to cloud computing.