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Realization of Fast All-Microwave Controlled-Z Gates with a Tunable Coupler

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Chinese Physics Letters 2022年第3期39卷 6-11页

作者： Shaowei Li Daojin Fan Ming Gong Yangsen Ye Xiawei Chen Yulin Wu Huijie Guan Hui Deng Hao Rong He-Liang Huang Chen Zha Kai Yan Shaojun Guo Haoran Qian Haibin Zhang Fusheng Chen Qingling Zhu Youwei Zhao Shiyu Wang Chong Ying Sirui Cao Jiale Yu Futian Liang Yu Xu Jin Lin Cheng Guo Lihua Sun Na Li Lianchen Han Cheng-Zhi Peng Xiaobo Zhu Jian-Wei Pan Department of Modern Physics University of Science and Technology of ChinaHefei 230026China Shanghai Branch CAS Center for Excellence in Quantum Information and Quantum PhysicsUniversity of Science and Technology of ChinaShanghai 201315China Shanghai Research Center for quantum Sciences Shanghai 201315China

The development of high-fidelity two-qubit quantum gates is essential for digital quantum ***,we propose and realize an all-microwave parametric controlled-Z(CZ)gates by coupling strength modulation in a superconducting Transmon qubit system with tunable *** optimizing the design of the tunable coupler together with the control pulse numerically,we experimentally realized a 100 ns CZ gate with high fidelity of 99.38%±0.34%and the control error being 0.1%.We note that our CZ gates are not affected by pulse distortion and do not need pulse correction,providing a solution for the real-time pulse generation in a dynamic quantum feedback *** the expectation of utilizing our all-microwave control scheme to reduce the number of control lines through frequency multiplexing in the future,our scheme draws a blueprint for the high-integrable quantum hardware design.

关键词： quantum microwave scheme

Variational quantum Algorithms for the Steady States of Open quantum Systems

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Chinese Physics Letters 2021年第8期38卷 11-16页

作者： Huan-Yu Liu Tai-Ping Sun Yu-Chun Wu Guo-Ping Guo Key Laboratory of quantum Information Chinese Academy of SciencesSchool of PhysicsUniversity of Science and Technology of ChinaHefei 230026China CAS Center For Excellence in quantum Information and quantum Physics University of Science and Technology of ChinaHefei 230026China Institute of Artificial Intelligence Hefei Comprehensive National Science CenterHefei 230088China Origin quantum Computing Hefei Hefei 230026China

The solutions of the problems related to open quantum systems have attracted considerable *** propose a variational quantum algorithm to find the steady state of open quantum *** this algorithm,we employ parameterized quantum circuits to prepare the purification of the steady state and define the cost function based on the Lindblad master equation,which can be efficiently evaluated with quantum *** then optimize the parameters of the quantum circuit to find the steady *** simulations are performed on the one-dimensional transverse field Ising model with dissipative *** result shows that the fidelity between the optimal mixed state and the true steady state is over 99%.This algorithm is derived from the natural idea of expressing mixed states with purification and it provides a reference for the study of open quantum systems.

关键词： state quantum mixed

Generation of multiphoton quantum states on silicon

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Light(Science & Applications) 2019年第1期8卷 811-817页

作者： 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 State Key Laboratory for Modern Optical Instrumentation Centre for Optical and Electromagnetic ResearchZhejiang Provincial Key Laboratory for Sensing TechnologiesCollege of Optical Science and EngineeringZhejiang UniversityZijingang CampusHangzhou 310058China Ningbo Research Institute Zhejiang UniversityNingbo 315100China Key Laboratory of quantum Information CASUniversity of Science and Technology of ChinaHefeiAnhui 230026China Synergetic Innovation Center of quantum Information&quantum Physics University of Science and Technology of ChinaHefeiAnhui 230026China

Multiphoton quantum states play a critical role in emerging quantum technologies and greatly improve our fundamental understanding of the quantum *** photonics is well recognized as an attractive technology offering great promise for the generation of photonic quantum states with high-brightness,tunability,stability,and ***,we demonstrate the generation of multiphoton quantum states using a single-silicon nanophotonic *** detected four-photon rate reaches 0.34 Hz even with a low-pump power of 600μ*** multiphoton quantum state is also qualified with multiphoton quantum interference,as well as quantum state *** the generated four-photon states,the quantum interference visibilities are greater than 95%,and the fidelity is 0.78±***,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.

关键词： quantum multiphoton realization

A mechanically tuned Kerr comb in a dispersion-engineered silica microbubble resonator

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Science China(Physics,Mechanics & Astronomy) 2020年第5期63卷 92-97页

作者： FangJie Shu PeiJi Zhang YanJun Qian ZhengYu Wang Shuai Wan Chang Ling Zou GuangCan Guo ChunHua Dong Department of Physics Shangqiu Normal Universiy Shangqius 476000.China FCAS Key Laboratory of quantum Information University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in quantum Information and quantum Physics University of Science and Technology of ChinaHefei 230026China

This paper discusses the developement and investigation of a silica microbubble resonator(MBR) that is optimized to cancel mode dispersion with material dispersion, at a wavelength of approximately 1550 nm and maintain a quality factor of an optical mode as large as 5.4 × 10~7. Benefitting from the near-zero dispersion and high quality factor, a primary optical comb is generated in the MBR using cascaded four-wave mixing processes, which span over 300 nm with several tens of teeth. Furthermore, the frequency comb could be gradually tuned by mechanically stretching the MBR. This tunable Kerr comb has multiple potential applications in precision measurements and sensing applications, such as molecular spectroscopy and ranging.

关键词： microresonator nonlinear optics frequency comb

Experimental demonstration of suppressing residual geometric dephasing

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Science Bulletin 2019年第23期64卷 1757-1763页

作者： Jin-Ming Cui Ming-Zhong Ai Ran He Zhong-Hua Qian Xiao-Ke Qin Yun-Feng Huang Zheng-Wei Zhou Chuan-Feng Li Tao Tu Guang-Can Guo CAS Key Laboratory of quantum Information University of Science and Technology of ChinaHefei 230026China CAS Center For Excellence in quantum Information and quantum Physics University of Science and Technology of ChinaHefei 230026China Luoyang Institute of Electro-Optical Equipment AVICLuoyang 471000China

The geometric phase is regarded as a promising strategy in fault tolerance quantum information processing(QIP) domain due to its phase only depending on the geometry of the path executed. However, decoherence caused by environmental noise will destroy the geometric phase. Traditional dynamic decoupling sequences can eliminate dynamic dephasing but can not reduce residual geometric dephasing, which is still vital for high-precision quantum manipulation. In this work, we experimentally demonstrate effective suppression of residual geometric dephasing with modified dynamic decoupling schemes,using a single trapped171 Ybtion. The experimental results show that the modified schemes can reduce dephasing rate up to more than one order of magnitude compared with traditional dynamic decoupling schemes, where residual geometric dephasing dominates. Besides, we also investigate the impact of intensity and correlation time of the low-frequency noise on coherence of the quantum system. And we confirm these methods can be used in many cases.

关键词： Geometric dephasing Berry phase Dynamic decoupling Ion trap

Optical demonstration of quantum fault-tolerant threshold

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Light(Science & Applications) 2022年第8期11卷 1834-1842页

作者： Kai Sun Ze-Yan Hao Yan Wang Jia-Kun Li Xiao-Ye Xu Jin-Shi Xu Yong-Jian Han Chuan-Feng Li Guang-Can Guo CAS Key Laboratory of quantum Information University of Science and Technology of ChinaHefei230026China CAS Center for Excellence in quantum Information and quantum Physics University of Science and Technology of ChinaHefei230026China Hefei National Laboratory University of Science and Technology of ChinaHefei230088China

A major challenge in practical quantum computation is the ineludible errors caused by the interaction of quantum systems with their environment. Fault-tolerant schemes, in which logical qubits are encoded by several physical qubits, enable to the output of a higher probability of correct logical qubits under the presence of errors. However, strict requirements to encode qubits and operators render the implementation of a full fault-tolerant computation challenging even for the achievable noisy intermediate-scale quantum technology. Especially the threshold for fault-tolerant computation still lacks experimental verification. Here, based on an all-optical setup, we experimentally demonstrate the existence of the threshold for the fault-tolerant protocol. Four physical qubits are represented as the spatial modes of two entangled photons, which are used to encode two logical qubits. The experimental results clearly show that when the error rate is below the threshold, the probability of correct output in the circuit, formed with fault-tolerant gates, is higher than that in the corresponding non-encoded circuit. In contrast, when the error rate is above the threshold, no advantage is observed in the fault-tolerant implementation. The developed high-accuracy optical system may provide a reliable platform to investigate error propagation in more complex circuits with fault-tolerant gates.

关键词： quantum error operators

Photoionisation detection of a single Er3+ ion with sub-100-ns time resolution

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National Science Review 2024年第4期11卷 38-45页

作者： Yangbo Zhang Wenda Fan Jiliang Yang Hao Guan Qi Zhang Xi Qin Changkui Duan Gabriele G.de Boo Brett C.Johnson Jeffrey C.Mc Callum Matthew J.Sellars Sven Rogge Chunming Yin Jiangfeng Du CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences University of Science and Technology of China CAS Center for Excellence in quantum Information and quantum Physics University of Science and Technology of China Hefei National Laboratory University of Science and Technology of China Centre of Excellence for quantum Computation and Communication Technology School of Physics University of New South Wales Centre of Excellence for quantum Computation and Communication Technology School of Engineering RMIT University Centre of Excellence for quantum Computation and Communication Technology School of Physics University of Melbourne Centre of Excellence for quantum Computation and Communication Technology Research School of Physics and Engineering Australian National University

Efficient detection of single optical centres in solids is essential for quantum information processing, sensing and single-photon generation *** this work,we use radio-frequency（RF） reflectometry to electrically detect the photoionisation induced by a single Er3+ion in *** high bandwidth and sensitivity of the RF reflectometry provide sub-100-ns time resolution for the photoionisation *** this technique,the optically excited state lifetime of a single Er3+ion in a Si nano-transistor is measured for the first time to be 0.49±0.04μ*** results demonstrate an efficient approach for detecting a charge state change induced by Er excitation and *** approach could be used for fast readout of other single optical centres in solids and is attractive for large-scale integrated optical quantum systems thanks to the multi-channel RF reflectometry demonstrated with frequency multiplexing techniques.

关键词： single optical centres erbium ions RF reflectometry photoionisation detection

Observation of the density dependence of the closed-channel fraction of a 6Li superfluid

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National Science Review 2022年第10期9卷 105-111页

作者： Xiang-Pei Liu Xing-Can Yao Hao-Ze Chen Xiao-Qiong Wang Yu-Xuan Wang Yu-Ao Chen Qijin Chen Kathryn Levin Jian-Wei Pan Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics University of Science and Technology of China Shanghai Branch CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai Research Center for quantum Sciences James Franck Institute University of Chicago

Atomic Fermi gases provide an ideal platform for studying pairing and superfluid physics,using a Feshbach resonance between closed-channel molecular states and open-channel scattering *** particular interest is the strongly interacting *** show that the closed-channel fraction Zccprovides an effective probe for important many-body interacting effects,especially through its density dependence,which is absent from two-body theoretical *** we measure Zccas a function of interaction strength and the Fermi temperature TF in a trapped 6Li superfluid throughout the entire Bardeen-Cooper-Schrieffer-Bose-Einstein-condensate crossover,in quantitative agreement with theory when important thermal contributions outside the superfluid core are taken into *** from the deep-BEC regime,the fraction Zccis sensitive to *** particular,our data show Zcc∝TFαwith α=1/2at unitarity,in quantitative agreement with calculations of a two-channel pairing fluctuation theory,and a increases rapidly into the BCS regime,reflecting many-body interaction effects as predicted.

关键词： closed-channel fraction density dependence strongly interacting Fermi gas many-body effect

Experimental verification of generalized eigenstate thermalization hypothesis in an integrable system

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Light(Science & Applications) 2022年第7期11卷 1615-1624页

作者： Qin-Qin Wang Si-Jing Tao Wei-Wei Pan Zhe Chen Geng Chen Kai Sun Jin-Shi Xu Xiao-Ye Xu Yong-Jian Han Chuan-Feng Li Guang-Can Guo CAS Key Laboratory of quantum Information University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in quantum Information and quantum Physics University of Science and Technology of ChinaHefei 230026China Hefei National Laboratory University of Science and Technology of ChinaHefei 230088China

Identifying the general mechanics behind the equilibration of a complex isolated quantum system towards a state described by only a few parameters has been the focus of attention in non-equilibrium *** several experimentally unproven conjectures are proposed for the statistical description of quantum(non-)integrable *** plausible eigenstate thermalization hypothesis(ETH),which suggests that each energy eigenstate itself is thermal,plays a crucial role in understanding the quantum thermalization in non-integrable systems;it is commonly believed that it does not exist in integrable ***,integrable systems can still relax to the generalized Gibbs *** a microscopic perspective,understanding the origin of this generalized thermalization that occurs in an isolated integrable system is a fundamental open question lacking experimental ***,we experimentally investigated the spin subsystem relaxation in an isolated spin-orbit coupling quantum *** applying the quantum state engineering technique,we initialized the system with various distribution widths in the mutual eigenbasis of the conserved ***,we compared the steady state of the spin subsystem reached in a long-time coherent dynamics to the prediction of a generalized version of ETH and the underlying mechanism of the generalized thermalization is experimentally verified for the first *** results facilitate understanding the origin of quantum statistical mechanics.

关键词： integrable quantum state