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quantum public-key crypto via EPR pairs

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 58-63页

作者： Xiang-Qun Fu Hong-Wei Li Jian-Hong Shi Tan Li Wan-Su Bao Henan Key Laboratory of quantum information and Cryptography Information Engineering University Synergetic Innovation center of quantum information and quantum Physics University of Science and Technology of China

With the development of quantum computing technology, quantum public-key cryptography is gradually becoming an alternative to the existing classical public-key cryptography. This paper designs a quantum trapdoor one-way function via EPR pairs and quantum measurements. Based on this, a new quantum public-key cryptosystem is presented, which offers forward security,and can resist the chosen-plaintext attack and chosen-ciphertext attack. Compared with the existing quantum public-key cryptos,eavesdropping can be automatically detected in this new quantum public-key cryptosystem under a necessary condition, which is also detailed in the paper.

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Experimental Hamiltonian Learning of an 11-Qubit Solid-State quantum Spin Register

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Chinese Physics Letters 2019年第10期36卷 11-16页

作者： P.-Y.Hou L.He F.Wang X.-Z.Huang W.-G.Zhang X.-L.Ouyang X.Wang W.-Q.Lian X.-Y.Chang L.-M.Duan center for quantum information Institute for Interdisciplinary Information SciencesTsinghua UniversityBeijing 100084

Learning the Hamiltonian of a quantum system is indispensable for prediction of the system dynamics and realization of high fidelity quantum ***,it is a significant challenge to efficiently characterize the Hamiltonian which has a Hilbert space dimension exponentially growing with the system ***,we develop and implement an adaptive method to learn the effective Hamiltonian of an 11-qubit quantum system consisting of one electron spin and ten nuclear spins associated with a single nitrogen-vacancy center in a *** validate the estimated Hamiltonian by designing universal quantum gates based on the learnt Hamiltonian and implementing these gates in the *** experimental result demonstrates a well-characterized 11-qubit quantum spin register with the ability to test quantum algorithms,and shows our Hamiltonian learning method as a useful tool for characterizing the Hamiltonian of the nodes in a quantum network with solid-state spin qubits.

关键词： Hamiltonian quantum system

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

Improved Superconducting Qubit State Readout by Path Interference

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Chinese Physics Letters 2021年第11期38卷 13-17页

作者： Zhiling Wang Zenghui Bao Yukai Wu Yan Li Cheng Ma Tianqi Cai Yipu Song Hongyi Zhang Luming Duan center for quantum information Institute for Interdisciplinary Information SciencesTsinghua UniversityBeijing 100084China

High fidelity single shot qubit state readout is essential for many quantum information processing protocols. In superconducting quantum circuit, the qubit state is usually determined by detecting the dispersive frequency shift of a microwave cavity from either transmission or reflection. We demonstrate the use of constructive interference between the transmitted and reflected signal to optimize the qubit state readout, with which we find a better resolved state discrimination and an improved qubit readout fidelity. As a simple and convenient approach, our scheme can be combined with other qubit readout methods based on the discrimination of cavity photon states to further improve the qubit state readout.

关键词： red Gaussian Improved Superconducting Qubit State Readout by Path Interference

Universal adversarial examples and perturbations for quantum classifiers

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National Science Review 2022年第6期9卷 48-55页

作者： Weiyuan Gong Dong-Ling Deng center for quantum information Institute for Interdisciplinary Information Sciences (ⅢS) Tsinghua University Shanghai Qi Zhi Institute

quantum machine learning explores the interplay between machine learning and quantum physics, which may lead to unprecedented perspectives for both fields. In fact, recent works have shown strong evidence that quantum computers could outperform classical computers in solving certain notable machine learning tasks. Yet, quantum learning systems may also suffer from the vulnerability problem: adding a tiny carefully crafted perturbation to the legitimate input data would cause the systems to make incorrect predictions at a notably high confidence level. In this paper, we study the universality of adversarial examples and perturbations for quantum classifiers. Through concrete examples involving classifications of real-life images and quantum phases of matter, we show that there exist universal adversarial examples that can fool a set of different quantum classifiers. We prove that, for a set of k classifiers with each receiving input data of n qubits, an O(ln [k]/2~n) increase of the perturbation strength is enough to ensure a moderate universal adversarial risk. In addition, for a given quantum classifier, we show that there exist universal adversarial perturbations, which can be added to different legitimate samples to make them adversarial examples for the classifier. Our results reveal the universality perspective of adversarial attacks for quantum machine learning systems, which would be crucial for practical applications of both near-term and future quantum technologies in solving machine learning problems.

关键词： quantum machine learning quantum classifiers adversarial examples measure concentration quantum no-free-lunch theorem

Theory of the magnon Kerr effect in cavity magnonics

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Science China(Physics,Mechanics & Astronomy) 2019年第8期62卷 93-103页

作者： GuoQiang Zhang YiPu Wang JianQiang You quantum Physics and quantum information Division Beijing Computational Science Research Center interdisciplinary center of quantum information and Zhejiang Province Key Laboratory of quantum Technology and Device Department of Physics and State Key Laboratory of Modern Optical Instrumentation Zhejiang University

We develop a theory for the magnon Kerr effect in a cavity magnonics system, consisting of magnons in a small yttrium iron garnet(YIG) sphere strongly coupled to cavity photons, and use it to study the bistability in this hybrid system. To have a complete picture of the bistability phenomenon, we analyze two different cases in driving the cavity magnonics system, i.e.,directly pumping the YIG sphere and the cavity, respectively. In both cases, the magnon frequency shifts due to the Kerr effect exhibit a similar bistable behavior but the corresponding critical powers are different. Moreover, we show how the bistability of the system can be demonstrated using the transmission spectrum of the cavity. Our results are valid in a wide parameter regime and generalize the theory of bistability in a cavity magnonics system.

关键词： magnon Kerr effect cavity magnonics bistability hybrid system

Observation of Topological Links Associated with Hopf Insulators in a Solid-State quantum Simulator

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Chinese Physics Letters 2017年第6期34卷 14-18页

作者：袁新星何丽王胜涛邓东灵王飞连文倩王歆张楚珩张慧丽常秀英段路明 center for quantum information Institute for Interdisciplinary Information SciencesTsinghua University Department of Physics University of Michigan Condensed Matter Theory center and Joint quantum Institute Department of PhysicsUniversity of Maryland

Hopf insulators are intriguing three-dimensional topological insulators characterized by an integer topological invariant. They originate from the mathematical theory of Hopf fibration and epitomize the deep connection between knot theory and topological phases of matter, which distinguishes them from other classes of topological insulators. Here, we implement a model Hamiltonian for Hopf insulators in a solid-state quantum simulator and report the first experimental observation of their topological properties, including nontrivial topological links associated with the Hopf fibration and the integer-valued topological invariant obtained from a direct tomographic measurement. Our observation of topological links and Hopf fibration in a quantum simulator opens the door to probe rich topological properties of Hopf insulators in experiments. The quantum simulation and probing methods are also applicable to the study of other intricate three-dimensional topological model Hamiltonians.

关键词： Observation of Topological Links Associated with Hopf Insulators in a Solid-State quantum Simulator

Hybrid opto-mechanical systems with nitrogen-vacancy centers

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Science China(Physics,Mechanics & Astronomy) 2015年第5期58卷 29-40页

作者： YIN ZhangQi ZHAO Nan LI TongCang center for quantum information Institute for Interdisciplinary Information Sciences Tsinghua University Beijing Computational Science Research center Synergetic Innovation center of quantum information and quantum Physics University of Science and Technology of China Department of Physics and Astronomy and School of Electrical and Computer Engineering Purdue University Birck Nanotechnology center Purdue University

In this review, we briefly review recent works on hybrid （nano） and diamond nitrogen-vacancy （NV） centers. We also review opto-mechanical systems that contain both mechanical oscillators two different types of mechanical oscillators. The first one is a clamped mechanical oscillator, such as a cantilever, with a fixed frequency. The second one is an optically trapped nano-diamond with a built-in nitrogen-vacancy center. By coupling mechanical resonators with electron spins, we can use the spins to control the motion of mechanical oscillators. For the first setup, we discuss two different coupling mechanisms, which are magnetic coupling and strain induced coupling. We summarize their applications such as cooling the mechanical oscillator, generating entanglements between NV centers, squeezing spin ensembles etc. For the second setup, we discuss how to generate quantum superposition states with magnetic coupling, and realize matter wave interferometer. We will also review its applications as ultra-sensitive mass spectrometer. Finally, we discuss new coupling mechanisms and applications of the field.

关键词： opto-mechanics nitrogen-vacancy center hybrid system

Experimental exploration of five-qubit quantum error-correcting code with superconducting qubits

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National Science Review 2022年第1期9卷 100-106页

作者： Ming Gong Xiao Yuan Shiyu Wang Yulin Wu Youwei Zhao Chen Zha Shaowei Li Zhen Zhang Qi Zhao Yunchao Liu Futian Liang Jin Lin Yu Xu Hui Deng Hao Rong He Lu Simon C.Benjamin Cheng-Zhi Peng Xiongfeng Ma Yu-Ao Chen 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 China Shanghai Branch CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai Research center for quantum Sciences center for quantum information Institute for Interdisciplinary Information Sciences Tsinghua University Department of Materials University of Oxford

quantum error correction is an essential ingredient for universal quantum computing.D espite tremendous experimental efforts in the study of quantum error correction,to date,there has been no demonstration in the realis ation of universal quantum error-correcting code,with the subsequent verification of all key features including the identification of an arbitrary physical error,the capability for transversal manipulation of the logical state and state *** address this challenge,we experimentally realise the [5,1,3]code,the so-called smallest perfect code that permits corrections of generic single-qubit *** the experiment,having optimised the encoding circuit,we employ an array of superconducting qubits to realise the [5,1,3] code for several typical logical states including the magic state,an indispensable resource for realising non-Clifford *** encoded states are prepared with an average fidelity of 57.1(3)% while with a high fidelity of 98.6(1)% in the code ***,the arbitrary single-qubit errors introduced manually are identified by measuring the *** further implement logical Pauli operations with a fidelity of 97.2(2)% within the code ***,we realise the decoding circuit and recover the input state with an overall fidelity of 74.5(6)%,in total with 92 *** work demonstrates each key aspect of the [5,1,3] code and verifies the viability of experimental realisation of quantum error-correcting codes with superconducting qubits.

关键词： quantum error-correcting code superconducting qubit five-qubit code error detection logical operation