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Efficient Scheme for Entanglement and quantum information processing with Two superconducting quantum-Interference Devices in Cavity QED

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Communications in Theoretical Physics 2007年第4期47卷 722-724页

作者： ZHAN Zhi-Ming School of Physics ＆ information Engineering Jianghan University Wuhan 430056 China

In this paper, a scheme is proposed to create the entanglement of two superconducting quantum-interference devices （SQUIDs） and implement a two-quhit quantum phase gate between two SQUIDs in cavity. The scheme only requires resonant interactions. Thus the scheme is very simple and the quantum dynamics operation can he realized at a high speed, which is important in view of decoherence.

关键词： entanglement superconducting cavity

Simple and practical method of characterizing the parametric down-conversion source

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Chinese Physics B 2017年第11期26卷 83-88页

作者：王东伍娟赵良圆安雪碧银振强陈巍韩正甫王琴 Key laboratory of quantum information University of Science and Technology of China Synergetic Innovation Center of quantum information & quantum Physics University of Science and Technology of China Institute of Signal processing and Transmission Nanjing University of Posts and Telecommunications

Parametric down-conversion（PDC） sources play an important role in quantum information processing, therefore characterizing their properties is necessary. Here we present a statistical model to assess the properties of the PDC source with certain distribution, such as the brightness and photon channel transmissions, we only need to measure the singles and coincidences counts in a few seconds. Furthermore, we validate the model by applying it to a PDC source generating highly non-degenerate photon pairs. The results of the experiment indicate that our method is more simple, efficient, and less time consuming.

关键词： parametric down-conversion brightness photon channel transmission

Multi-Mode Bus Coupling Architecture of superconducting quantum Processor

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Chinese Physics Letters 2023年第1期40卷 1-8页

作者：赵昌昊何永成耿霄何楷泳戴根婷刘建设陈炜 laboratory of superconducting quantum information processing School of Integrated CircuitsTsinghua UniversityBeijing 100084China Beijing National Research Center for information Science and Technology Beijing 100084China Beijing Innovation Center for Future Chips Tsinghua UniversityBeijing 100084China

Resonators in circuit quantum electrodynamics systems naturally carry multiple modes, which may have non-negligible influence on qubit parameters and device performance. While new theories and techniques are under investigation to deal with the multi-mode effects in circuit quantum electrodynamics systems, researchers have proposed novel engineering designs featuring multi-mode resonators to achieve enhanced functionalities of superconducting quantum processors. Here, we propose multi-mode bus coupling architecture, in which superconducting qubits are coupled to multiple bus resonators to gain larger coupling strength. Applications of multi-mode bus couplers can be helpful for improving i SWAP gate fidelity and gate speed beyond the limit of single-mode scenario. The proposed multi-mode bus coupling architecture is compatible with a scalable variation of the traditional bus coupling architecture. It opens up new possibilities for realization of scalable superconducting quantum computation with circuit quantum electrodynamics systems.

关键词： quantum coupling negligible

Simulations of superconducting quantum gates by digital flux tuner for qubits

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Chinese Physics B 2024年第7期33卷 210-222页

作者：耿霄何楷泳刘建设陈炜 laboratory of superconducting quantum information processing School of Integrated CircuitsTsinghua UniversityBeijing 100084China Beijing Innovation Center for Future Chips Tsinghua UniversityBeijing 100084China Beijing National Research Center for information Science and Technology Beijing 100084China26

The interconnection bottleneck caused by limitations of cable number, inner space and cooling power of dilution refrigerators has been an outstanding challenge for building scalable superconducting quantum computers with the increasing number of qubits in quantum processors. To surmount such an obstacle, it is desirable to integrate qubits with quantum–classical interface(QCI) circuits based on rapid single flux quantum(RSFQ) circuits. In this work, a digital flux tuner for qubits(DFTQ) is proposed for manipulating flux of qubits as a crucial part of the interface circuit. A schematic diagram of the DFTQ is presented, consisting of a coarse tuning unit and a fine-tuning unit for providing magnetic flux with different precision to qubits. The method of using DFTQ to provide flux for gate operations is discussed from the optimization of circuit design and input signal. To verify the effectiveness of the method, simulations of a single DFTQ and quantum gates including a Z gate and an iSWAP gate with DFTQs are performed for flux-tunable transmons. The quantum process tomography corresponding to the two gates is also carried out to analyze the sources of gate error. The results of tomography show that the gate fidelities independent of the initial states of the Z gate and the iSWAP gate are 99.935% and 99.676%,respectively. With DFTQs inside, the QCI would be a powerful tool for building large-scale quantum computers.

关键词： quantum computation superconducting electronics quantum control

Hybrid quantum private communication with continuous-variable and discrete-variable signals

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Science China(Physics,Mechanics & Astronomy) 2015年第2期58卷 14-20页

作者： LIU WeiQi PENG JinYe WANG Chao CAO ZhengWen HUANG Duan LIN DaKai HUANG Peng ZENG GuiHua College of information Science and Technology Northwest University State Key laboratory of Advanced Optical Communication Systems and Networks and Center of Quantum Information Sensing and ProcessingShanghai Jiaotong University

The quantum key distribution(QKD) has been entering the practical application era. Subsequently, hybrid quantum private communication with discrete-variable signals, continuous-variable signals, and classic optical signals becomes inevitable in the practical scenario. In this paper, we experimentally investigated the mutual effects between the discrete-variable QKD(DVQKD) and the continuous-variable QKD(CVQKD) via a fiber channel. The experimental results show that the DVQKD will be influenced by the continuous-variable quantum signals and classic optical signals, while the CVQKD is not sensitive to the discrete-variable quantum signals.

关键词： hybrid quantum private communication Gaussian-modulated CVQKD protocol BB84 protocol mutual influences

Efficient stochastic successive cancellation list decoder for polar codes

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Science China(information Sciences) 2020年第10期63卷 133-151页

作者： Xiao LIANG Huizheng WANG Yifei SHEN Zaichen ZHANG Xiaohu YOU Chuan ZHANG laboratory of Efficient Architectures for Digital-communication and Signal-processing (LEADS) Southeast University National Mobile Communications Research laboratory Southeast University quantum information Center of Southeast University

Polar codes are one of the most favorable capacity-achieving codes owing to their simple structures and low decoding complexity. Successive cancellation list(SCL) decoders with large list sizes achieve performances very close to those of maximum-likelihood(ML) decoders. However, hardware cost is a severe problem because an SCL decoder with list size L consists of L copies of a successive cancellation(SC)decoder. To address this issue, a stochastic SCL(SSCL) polar decoder is proposed. Although stochastic computing can achieve a good hardware reduction compared with the deterministic one, its straightforward application to an SCL decoder is not well-suited owing to the precision loss and severe latency. Therefore,a doubling probability approach and adaptive distributed sorting(DS) are introduced. A corresponding hardware architecture is also developed. Field programmable gate array(FPGA) results demonstrate that the proposed stochastic SCL polar decoder can achieve a good performance and complexity tradeoff.

关键词： SCL polar decoder stochastic computing 2-bit decoding distributed sorting hardware

A scheme for two-photon lasing with two coupled flux qubits in circuit quantum electrodynamics

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Chinese Physics B 2015年第6期24卷 353-359页

作者：黄文邹旭波郭光灿 Key laboratory of quantum information University of Science and Technology of China Synergetic Innovation Center of quantum information and quantum Physics University of Science and Technology of China

We theoretically study the system of a superconducting transmission line resonator coupled to two interacting super- conducting flux qubits. It is shown that under certain conditions the resonator mode can be tuned to two-photon resonance between the ground state and the highest excited state while the middle excited states are far-off resonance. Furthermore, we study the steady-state properties of the flux qubits and resonator, such as the photon statistics, the spectrum and squeezing of the resonator, and demonstrate that two-photon laser can be implemented with current experimental technology.

关键词： circuit quantum electrodynamics two-photon laser superconducting Josephson junction

Deformed photon-added entangled squeezed vacuum and one-photon states: Entanglement, polarization, and nonclassical properties

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Chinese Physics B 2016年第4期25卷 47-56页

作者： A Karimi M K Tavassoly Atomic and Molecular Group Faculty of Physics Yazd University Physics Group Islamic Azad University of Abadeh The laboratory of quantum information processing Yazd University

In this paper, after a brief review on the entangled squeezed states, we produce a new class of the continuous-variable- type entangled states, namely, deformed photon-added entangled squeezed states. These states are obtained via the iterated action of the f-deformed creation operator A = f（n）a＋ on the entangled squeezed states. In the continuation, by studying the criteria such as the degree of entanglement, quantum polarization as well as sub-Poissonian photon statistics, the two- mode correlation function, one-mode and two-mode squeezing, we investigate the nonclassical behaviors of the introduced states in detail by choosing a particular f-deformation function. It is revealed that the above-mentioned physical properties can be affected and so may be tuned by justifying the excitation number, after choosing a nonlinearity function. Finally, to generate the introduced states, we propose a theoretical scheme using the nonlinear Jaynes-Cummings model.

关键词： squeezed states deformed photon-added entangled states entanglement quantum polarization

Experimental repetitive quantum channel simulation

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Science Bulletin 2018年第23期63卷 1551-1557页

作者： Ling Hu Xianghao Mu Weizhou Cai Yuwei Ma Yuan Xu Haiyan Wang Yipu Song Chang-Ling Zou Luyan Sun Center for quantum information Institute for Interdisciplinary Information Sciences Tsinghua University Key laboratory of quantum information CAS University of Science and Technology of China

Universal control of quantum systems is a major goal to be achieved for quantum information processing,which demands thorough understanding of fundamental quantum mechanics and promises applications of quantum technologies. So far, most studies concentrate on ideally isolated quantum systems governed by unitary evolutions, while practical quantum systems are open and described by quantum channels due to their inevitable coupling to environment. Here, we experimentally simulate arbitrary quantum channels for an open quantum system, i.e. a single photonic qubit in a superconducting quantum *** arbitrary channel simulation is achieved with minimum resource of only one ancilla qubit and measurement-based adaptive control. By repetitively implementing the quantum channel simulation,we realize an arbitrary Liouvillian for a continuous evolution of an open quantum system for the first time. Our experiment provides not only a testbed for understanding quantum noise and decoherence,but also a powerful tool for full control of practical open quantum systems.

关键词： quantum channel simulation Open quantum system Adaptive quantum control superconducting quantum computation