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Fast implementation of length-adaptive privacy amplification in quantum key distribution

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Chinese Physics B 2014年第9期23卷 112-117页

作者：张春梅李默黄靖正 Patcharapong Treeviriyanupab 李宏伟李芳毅王川银振强陈巍 Keattisak Sripimanwat 韩正甫 Key laboratory of quantum information Chinese Academy of Sciences University of Science and Technology of China Optical and quantum Communications (OQC) laboratory National Electronics and Computer Technology Center (NECTEC)National Science and Technology Development Agency (NSTDA)

Post-processing is indispensable in quantum key distribution （QKD）, which is aimed at sharing secret keys between two distant parties. It mainly consists of key reconciliation and privacy amplification, which is used for sharing the same keys and for distilling unconditional secret keys. In this paper, we focus on speeding up the privacy amplification process by choosing a simple multiplicative universal class of hash functions. By constructing an optimal multiplication algorithm based on four basic multiplication algorithms, we give a fast software implementation of length-adaptive privacy amplification. ＂Length-adaptive＂ indicates that the implementation of privacy amplification automatically adapts to different lengths of input blocks. When the lengths of the input blocks are 1 Mbit and 10 Mbit, the speed of privacy amplification can be as fast as 14.86 Mbps and 10.88 Mbps, respectively. Thus, it is practical for GHz or even higher repetition frequency QKD systems.

关键词： length-adaptive privacy amplification multiplication algorithms quantum key distribution

Observation of Coulomb Gap and Enhanced superconducting Gap in Nano-Sized Pb Islands Grown on SrTiO3

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Chinese Physics Letters 2020年第1期37卷 78-82页

作者： Yonghao Yuan Xintong Wang Canli Song Lili Wang Ke He Xucun Ma Hong Yao Wei Li Qi-Kun Xue State Key laboratory of Low-Dimensional quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084 Frontier Science Center for quantum information Beijing 100084 Institute for Advanced Study Tsinghua UniversityBeijing 100084 Beijing Academy of quantum information Sciences Beijing 100193

We report high-resolution scanning tunneling microscopy(STM)study of nano-sized Pb islands grown on SrTiO3,where three distinct types of gaps with different energy scales are *** low temperature,we find that the superconducting gap(△s)in nano-sized Pb islands is significantly enhanced from the one in bulk Pb,while there is no essential change in superconducting transition temperature Tc,giving rise to a larger BCS ratio 2△s/kBTc^8.31 and implying stronger electron-phonon *** stronger coupling can originate from the interface electron-phonon interactions between Pb islands and *** the superconducting gap is totally suppressed under applied magnetic field,the Coulomb gap with apparent V-shape ***,the size of Coulomb gap(Ac)depends on the lateral size of Pb islands(R)with △c-1/R^035,indicating that quantum size effect can significantly influence electronic *** experimental results shall shed important light on the interplay among superconductivity,quantum size effect and correlations in nano-sized strong-coupling superconductors.

关键词： sized stronger phonon

Significantly enhanced superconductivity in monolayer FeSe films on SrTiO3（001） via metallic δ-doping

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National Science Review 2024年第3期11卷 119-127页

作者： Xiaotong Jiao Wenfeng Dong Mingxia Shi Heng Wang Cui Ding Zhongxu Wei Guanming Gong Yanan Li Yuanzhao Li Binjie Zuo Jian Wang Ding Zhang Minghu Pan Lili Wang Qi-Kun Xue State Key laboratory of Low-Dimensional quantum Physics Department of Physics Tsinghua University School of Physics&information Technology Shaanxi Normal University Beijing Academy of quantum information Sciences Department of Physics Southern University of Science and Technology International Center for quantum Materials School of Physics Peking University Department of Physics The Pennsylvania State University Collaborative Innovation Center of quantum Matter Hefei National laboratory

Superconductivity transition temperature（Tc） marks the inception of a macroscopic quantum phase-coherent paired state in fermionic systems. For 2D superconductivity, the paired electrons condense into a coherent superfluid state at Tc, which is usually lower than the pairing temperature, between which intrinsic physics including Berezinskii–Kosterlitz–Thouless transition and pseudogap state are hotly debated. In the case of monolayer FeSe superconducting films on SrTiO3（001）, although the pairing temperature（Tp） is revealed to be 65–83 K by using spectroscopy characterization, the measured zero-resistance temperature（Tc0） is limited to 20 K. Here, we report significantly enhanced superconductivity in monolayer FeSe films by δ-doping of Eu or Al on SrTiO3（001） surface, in which Tc0is enhanced by 12 K with a narrowed transition width ΔTc～8 K, compared with non-doped samples. Using scanning tunneling microscopy/spectroscopy measurements, we demonstrate lowered work function of the δ-doped SrTiO3（001） surface and enlarged superconducting gaps in the monolayer FeSe with improved morphology/electronic homogeneity. Our work provides a practical route to enhance 2D superconductivity by using interface engineering.

关键词： monolayer FeSe interface superconductivity δ-doping zero-resistance temperature superconductivity transition temperature

Photorefractive Effect in a CdS Nanoparticlessensitized Polymer Composite

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Journal of Wuhan University of Technology(Materials Science) 2007年第4期22卷 638-642页

作者：丁莉芸姜德生 Key laboratory of Fiber Optic Sensing Technology and information processing(Ministry of Education) Wuhan University of Technology

The photorefractive （PR） performance of an organic/inorganic hybrid polymer composite sensitized by CdS nanoparticles, combining poly（N-vinylcarbazole）（PVK）, the second-order optically nonlinear chromophore 1-n-butoxy-2-methyl-（4-p-nitropheylazo）benzene （BMNPAB） and 9-ethylcarbazole （ECZ） was studied. It was confirmed that the CdS colloidal particles had a nanoscale size and quantum confinement effect adopting transmission electron microscopy and UV-Vis absorption spectroscopy. The addition of CdS nanoparticles as a photosensitizer in PVK will be significant enhancement of photoconductivity because of the high photocharge generation quantum efficiency and high charge transport to conducting polymer. The polymer composite film exhibited PR effect with a method of two-beam coupling experiment. And an asymmetric two. beam coupling gain of 45.8 cm^-1 without applied electric filed is obtained at 632.8 nm wavelength.

关键词： photorefi-active polymer PVK/CdS nanocomposite photoconductivity two-beam coupling

Room-temperature coherent manipulation of single-spin qubits in silicon carbide with a high readout contrast

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National Science Review 2022年第5期9卷 89-98页

作者： Qiang Li Jun-Feng Wang Fei-Fei Yan Ji-Yang Zhou Han-Feng Wang He Liu Li-Ping Guo Xiong Zhou Adam Gali Zheng-Hao Liu Zu-Qing Wang Kai Sun Guo-Ping Guo Jian-Shun Tang Hao Li Li-Xing You Jin-Shi Xu Chuan-Feng Li Guang-Can Guo CAS Key laboratory of quantum information University of Science and Technology of China CAS Center for Excellence in quantum information and quantum Physics University of Science and Technology of China Key laboratory of Artificial Micro-and Nano-structures of Ministry of Education and School of Physics and Technology Wuhan University Department of Atomic Physics Budapest University of Technology and Economics Wigner Research Centre for Physics State Key laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences(CAS)

Spin defects in silicon carbide(SiC) with mature wafer-scale fabrication and micro/nano-processing technologies have recently drawn considerable *** room-temperature single-spin manipulation of colour centres in SiC has been demonstrated,the typically detected contrast is less than 2%,and the photon count rate is also ***,we present the coherent manipulation of single divacancy spins in 4 H-SiC with a high readout contrast(-30%) and a high photon count rate(150 kilo counts per second)under ambient conditions,which are competitive with the nitrogen-vacancy centres in *** between a single defect spin and a nearby nuclear spin is also *** further provide a theoretical explanation for the high readout contrast by analysing the defect levels and decay *** the high readout contrast is of utmost importance in many applications of quantum technologies,this work might open a new territory for SiC-based quantum devices with many advanced properties of the host material.

关键词： silicon carbide single divacancy defects spin coherent control high readout contrast bright photon emission

In situ non-destructive measurement of Josephson junction resistance using fritting contact technique

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Chinese Physics B 2024年第11期33卷 57-61页

作者： Lei Du Hao-Ran Tao Liang-Liang Guo Hai-Feng Zhang Yong Chen Xin Tian Chi Zhang Zhi-Long Jia Peng Duan Guo-Ping Guo CAS Key laboratory of quantum information University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence and Synergetic Innovation Center in quantum information and quantum Physics University of Science and Technology of ChinaHefei 230026China Origin quantum Computing Technology (Hefei) Co. Ltd.Hefei 230088China

Conventional four-probe methods for measuring the resistance of Josephson junctions can damage superconducting thin films,making them unsuitable for frequency measurements of superconducting *** this study,we present a custom probe station measurement system that employs the fritting contact technique to achieve in situ,non-destructive measurements of Josephson junction *** experimental results demonstrate that this method allows for accurate prediction of qubit frequency with an error margin of 17.2 ***,the fritting contact technique does not significantly affect qubit coherence time or the integrity of the superconducting film,confirming its non-destructive *** innovative approach provides a dependable foundation for frequency tuning and addressing frequency collision issues,thus supporting the advancement and practical deployment of superconducting quantum computing.

关键词： non-destructive fritting contact qubit frequency Josephson junction resistance

The quantum Ising model for perfect matching and solving it with variational quantum eigensolver

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Science China(information Sciences) 2024年第9期67卷 306-320页

作者： Qilin ZHENG Pingyu ZHU Chao WU Miaomiao YU Weihong LUO Ping XU Institute for quantum information and State Key laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Hefei National laboratory

Obtaining all perfect matchings of a graph is a tough problem in graph theory, and its complexity belongs to the #P-Complete class. The problem is closely related to combinatorics, marriage matching problems, dense subgraphs, the Gaussian boson sampling, chemical molecular structures, and dimer *** this paper, we propose a quadratic unconstrained binary optimization formula of the perfect matching problem and translate it into the quantum Ising model. We can obtain all perfect matchings by mapping them to the ground state of the quantum Ising Hamiltonian and solving it with the variational quantum eigensolver. Adjusting the model's parameters can also achieve the maximum or minimum weighted perfect matching. The experimental results on a superconducting quantum computer of the Origin quantum Computing Technology Company show that our model can encode 2~n dimensional optimization space with only O（n） qubits consumption and achieve a high success probability of the ground state corresponding to all perfect matchings. In addition, the further simulation results show that the model can support a scale of more than 14 qubits, effectively resist the adverse effects of noise, and obtain a high success probability at a shallow variational depth. This method can be extended to other combinatorial optimization problems.

关键词： perfect matching Ising model quantum Hamiltonian variational quantum eigensolver quadratic unconstrained binary optimization

Realization of High-Fidelity Controlled-Phase Gates in Extensible superconducting Qubits Design with a Tunable Coupler

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Chinese Physics Letters 2021年第10期38卷 1-5页

作者： Yangsen Ye Sirui Cao Yulin Wu Xiawei Chen Qingling Zhu Shaowei Li Fusheng Chen Ming Gong Chen Zha He-Liang Huang Youwei Zhao Shiyu Wang Shaojun Guo Haoran Qian Futian Liang Jin Lin Yu Xu Cheng Guo Lihua Sun Na Li Hui Deng Xiaobo Zhu Jian-Wei Pan Hefei National laboratory for Physical Sciences at the Microscale and 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 Henan Key laboratory of quantum information and Cryptography Zhengzhou 450000China

High-fidelity two-qubit gates are essential for the realization of large-scale quantum computation and *** coupler design is used to reduce the problem of parasitic coupling and frequency crowding in manyqubit systems and thus thought to be advantageous. Here we design an extensible 5-qubit system in which center transmon qubit can couple to every four near-neighboring qubits via a capacitive tunable coupler and experimentally demonstrate high-fidelity controlled-phase(CZ) gate by manipulating central qubit and one nearneighboring qubit. Speckle purity benchmarking and cross entropy benchmarking are used to assess the purity fidelity and the fidelity of the CZ gate. The average purity fidelity of the CZ gate is 99.69±0.04% and the average fidelity of the CZ gate is 99.65±0.04%, which means that the control error is about 0.04%. Our work is helpful for resolving many challenges in implementation of large-scale quantum systems.

关键词： purity neighboring quantum

Absence of State Collapse and Revival in a superconducting Charge Qubit

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Communications in Theoretical Physics 2007年第12期48卷 1029-1032页

作者： HUO Wen-Yi~1 and LONG Gui-Lu~(1,2,3)~1 Department of Physics amd Key laboratory for quantum information and Measurements,Tsinghua University,Beijing100084,China~2 Key laboratory for Atomic and Molecular Nanosciences,Tsinghua University,Beijing 100084,China~3 National laboratory for information Science and Technology,Hsinghua University,Beijing 100084,China Department of Physics amd Key laboratory for quantum information and Measurements Tsinghua University Key laboratory for Atomic and Molecular Nanosciences Tsinghua University National laboratory for information Science and Technology Hsinghua Univers

The Hamiltonian of a superconducting charge qubit with a configuration of dc SQUID contains an interac-tion between the LC oscillator part and charge *** interaction may leads to quantum state collapse and revivalwhich degrades the charge qubits and leads to serious *** analysis shows that the existing charge qubitparameters do not lead to this phenomenon,which is very good for the superconducting charge

关键词： quantum computer superconducting charge qubit absence and revival