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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

Solving the subset sum problem by the quantum Ising model with variational quantum optimization based on conditional values at risk

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Science China(Physics,Mechanics & Astronomy) 2024年第8期67卷 43-55页

作者： Qilin Zheng Miaomiao Yu pingyu zhu Yan Wang Weihong Luo Ping Xu Institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computer Science and TechnologyNational University of Defense TechnologyChangsha 410073China Hefei National Laboratory Hefei 230088China

The subset sum problem is a combinatorial optimization problem,and its complexity belongs to the nondeterministic polynomial time complete(NP-Complete)*** problem is widely used in encryption,planning or scheduling,and integer *** accurate search algorithm with polynomial time complexity has not been found,which makes it challenging to be solved on classical *** effectively solve this problem,we translate it into the quantum Ising model and solve it with a variational quantum optimization method based on conditional values at *** proposed model needs only n qubits to encode 2ndimensional search space,which can effectively save the encoding quantum *** model inherits the advantages of variational quantum algorithms and can obtain good performance at shallow circuit depths while being robust to noise,and it is convenient to be deployed in the Noisy Intermediate Scale Quantum *** investigate the effects of the scalability,the variational ansatz type,the variational depth,and noise on the ***,we also discuss the performance of the model under different conditional values at *** computer simulation,the scale can reach more than nine *** selecting the noise type,we construct simulators with different QVs and study the performance of the model with *** addition,we deploy the model on a superconducting quantum computer of the Origin Quantum Technology Company and successfully solve the subset sum *** model provides a new perspective for solving the subset sum problem.

关键词： subset sum problem quantum Ising model conditional values at risk variational quantum optimization

On-chip quantum NOON state sensing for temperature and humidity

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Chinese Physics B 2024年第10期33卷 15-20页

作者： Weihong Luo Chao Wu Yuxing Du Chang Zhao Miaomiao Yu pingyu zhu Kaikai Zhang Ping Xu Institute for Quantum Information&State Key Laboratory of High Performance Computing College of Computer Science and TechnologyNational University of Defense TechnologyChangsha 410073China

A maximal photon number entangled state,namely NOON state,can be adopted for sensing with a quantum *** this work,we designed silicon quantum photonic chips containing two types of Mach-Zehnder interferometerswherein the two-photon NOON state,sensing element for temperature or humidity,is *** with classicallight or single photon case,two-photon NOON state sensing shows a solid enhancement in the sensing resolution *** the first demonstration of on-chip quantum photonic sensing,it reveals the advantages of photonic chips forhigh integration density,small-size,stability for multiple-parameter sensing serviceability.A higher sensing precision isexpected to beat the standard quantum limit with a higher photon number NOON state.

关键词： quantum sensing NOON state photonic chip

Quantum algorithm and experimental demonstration for the subset sum problem

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Science China(Information Sciences) 2022年第8期65卷 261-274页

作者： Qilin ZHENG pingyu zhu Shichuan XUE Yang WANG Chao WU Xinyao YU Miaomiao YU Yingwen LIU Mingtang DENG Junjie WU Ping XU Institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computer Science and TechnologyNational University of Defense Technology

To solve the subset sum problem, a well-known nondeterministic polynomial-time complete problem that is widely used in encryption and resource scheduling, we propose a feasible quantum algorithm that utilizes fewer qubits to encode and achieves quadratic speedup. Specifically, this algorithm combines an amplitude amplification algorithm with quantum phase estimation, and requires n + t + 1 qubits and O(2(0.5+o(1))n) operations to obtain the solution, where n is the number of elements, and t is the number of qubits used to store the eigenvalues. To verify the performance of the algorithm, we simulate the algorithm with the online quantum simulator of IBM named ibmq simulator using Qiskit and then run it on two IBM quantum computers called ibmq santiago and ibmq bogota. The experimental results indicate that compared with the brute force algorithm, the proposed algorithm results in quadratic acceleration for the problem of a set S with four elements and two subsets whose sum equals target w. Using the iterator twice, we obtain success probabilities of 0.940 ± 0.004, 0.751 ± 0.040, and 0.665 ± 0.060 on the simulator, ibmq santiago, and ibmq bogota, respectively, and the fidelity between the theoretical and experimental quantum states is calculated to be 0.944 ± 0.002, 0.753 ± 0.017, and 0.657 ± 0.028, respectively. If the error rates of the experimental quantum logic gates can be reduced, the success probabilities of the proposed algorithm on real quantum devices can be further improved.

关键词： quantum algorithm subset sum quadratic speedup encryption algorithm complexity

On-chip multiphoton Greenberger-Horne Zeilinger state based on integrated frequency combs

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Frontiers of physics 2020年第6期15卷 33-41页

作者： pingyu zhu Qilin Zheng Shichuan Xue Chao Wu Xinyao Yu Yang Wang Yingwen Liu Xiaogang Qiang Junjie Wu Ping Xu Institute for Quantum Information and State Key Laboratory of High Performance Computing College of ComputerNational University of Defense TechnologyChangsha 410073China National Innovation Institute of Defense Technology AMSBeijing 100071China National Laboratory of Solid State Micro structures and School of Physics Nanjing UniversityNanjing 210093China

One of the most important multipartite entangled states,Greenberger-Horne-Zeilinger state(GHZ),serves as a fundamental resource for quantum foundat ion test,quantum communication and quantum *** increase the number of entangled particles,significant experimental efforts should been invested due to the complexity of optical setup and the difficulty in maintaining the coherence condition for high-fidelity GHZ ***,we propose an ultra-integrated scalable on-chip GHZ state generation scheme based on frequency *** designing several microrings pumped by different lasers,multiple partially overlapped quantum frequency combs are generated to supply as the basis for on-chip polarization-encoded GHZ state with each qubit occupying a certain spectral *** even and odd numbers of GHZ states can be engineered with constant small number of integrated components and easily scaled up on the same chip by only adjusting one of the pumnp *** addition,we give the on-chip design of projection measurement for characterizing GHZ states and show the reconfigurability of the *** proposal is rather simple and feasible within the existing fabrication technologies and we believe it will boost the development of multiphoton technologies.

关键词： quantum information Greenberger-Horne Zeilinger state frequency comb

Improving the spectral purity of single photons by a single-interferometer-coupled microring

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Chinese Physics B 2022年第3期31卷 311-315页

作者： Yang Wang pingyu zhu Shichuan Xue Yingwen Liu Junjie Wu Xuejun Yang Ping Xu Institute for Quantum Information & State Key Laboratory of High Performance Computing College of Computer Science and TechnologyNational University of Defense TechnologyChangsha 410013China

We experimentally engineer a high-spectral-purity single-photon source using a single-interferometer-coupled silicon microring. By the reconfiguration of the interferometer, different coupling conditions can be obtained, corresponding to different quality factors for the pump and signal/idler. The ratio between the quality factor of the pump and signal/idler ranges from 0.29 to 2.57. By constructing the signal–idler joint spectral intensity, we intuitively demonstrate the spectral correlation of the signal and idler. As the ratio between the quality factor of the pump and signal/idler increases, the spectral correlation of the signal and idler decreases, i.e., the spectral purity of the signal/idler photons increases. Furthermore,time-integrated second-order correlation of the signal photons is measured, giving a value up to 94.95 ± 3.46%. Such high-spectral-purity photons will improve the visibility of quantum interference and facilitate the development of on-chip quantum information processing.

关键词： spectral-purity microring asymmetric Mach–Zehnder interferometer

Boosting the dimensionality of frequency entanglement using a reconfigurable microring resonator

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Science China(Physics,Mechanics & Astronomy) 2023年第5期66卷 79-88页

作者： Chao Wu Qilin Zheng Yingwen Liu Yang Wang Jiangfang Ding pingyu zhu Shichuan Xue Miaomiao Yu Weihong Luo Kaikai Zhang Anqi Huang Mingtang Deng Junjie Wu Ping Xu Institute for Quantum Information State Key Laboratory of High Performance ComputingCollege of Computer Science and TechnologyNational University of Defense TechnologyChangsha 410073China National Laboratory of Solid State Microstructures School of PhysicsNanjing UniversityNanjing 210093China

Integrated quantum frequency combs(QFCs)based on microring resonators supplies as an essential resource for expanding the Hilbert-space dimensionality for high-dimensional quantum computing and information *** this work,we propose and demonstrate a reconfigurable ring resonator with tunable quality factors to efficiently increase the dimensionality of frequency entanglement,simultaneously,ensuring a high on-chip pair generation rate(PGR)and coincidence-to-accidental ratio(CAR).Our method exploits the asymmetric Mach-Zehnder interferometer instead of the traditional straight waveguide as the coupler of resonators which offer a tunable external coupling coefficient to modulate the quality factor to enlarge the QFCs’bandwidth and thus increase the dimensionality of frequency *** measured the QFCs’joint spectral intensity of 28 frequency pairs under various quality factors ranging from 16.6×10^(4) to 3.4×10^(4).Meanwhile,the measured Schmidt number increased from 11.01 to 24.77,denoting a huge expansion of the Hilbert-space dimensionality from 121 to a record number of 613 dimensions,which agrees well with our theoretical *** addition,the PGR and CAR-another two key parameters for high-quality QFCs-were all measured under different quality factors to verify that our method can significantly increase the Schmidt number and CAR while maintaining a high *** fact,bright QFCs with a total PGR of 4.3 MHz under a 0.48 mW pump power and a mean CAR of 1578 were simultaneously obtained at the highest Schmidt *** method is widely applicable to other material-based ring resonators and can act as a general solution for high-dimensional QFCs.

关键词： reconfigurable resonator quantum frequency comb Hilbert-space dimensionality

Strain-Insensitive Fiber Bragg Grating Composite Structure for Wide-Range Temperature Sensing

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Journal of Dynamics, Monitoring and Diagnostics 2024年第3期3卷 199-206页

作者： pingyu zhu Tingyu Huang Sheng Fan Yukun Yan Bo Peng Danli Xiong Shuai Zhang Marcelo A.Soto School of Mechanical and Electrical Engineering Guangzhou UniversityGuangzhouChina zhuzhou Times New Material Technology Co. LtD.ZhuzhouChina Department of Electronics Engineering Universidad Técnica Federico Santa MaríaValparaísoChile

This paper reports on the design,fabrication,and temperature strain sensing performance of a fiber Bragg grating composite structure for surface mounted temperature measurements over a wide temperature range,with highly reduced strain *** fiber Bragg grating sensor is encapsulated in a polyimide tube filled with epoxy resin,forming an arc-shaped *** assembly is then placed between two layers of glass fiber prepreg with a flexible pad in between and cured into *** results,supported by finite element simulations,demonstrate an enhanced temperature sensitivity is 26.3 pm/°C over a wide temperature range of–30°C to 70°C,and high strain transfer isolation of about 99.65%.

关键词： composite structure fiber bragg grating temperature sensing

Near 100%spectral-purity photons from reconfigurable micro-rings

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Chinese Physics B 2020年第11期29卷 135-139页

作者： pingyu zhu Yingwen Liu Chao Wu Shichuan Xue Xinyao Yu Qilin Zheng Yang Wang Xiaogang Qiang Junjie Wu Ping Xu Institute for Quantum Information&State Key Laboratory of High Performance Computing College of ComputerNational University of Defense TechnologyChangsha 410073China National Innovation Institute of Defense Technology AMSBeijing 100071China National Laboratory of Solid State Microstructures and School of Physics Nanjing UniversityNanjing 210093China

We propose an on-chip reconfigurable micro-ring to engineer the spectral-purity of *** micro-ring resonator is designed to be coupled by one or two asymmetric Mach-Zehnder interferometers and the coupling coefficients hence the quality-factors of the pump and the converted photons can be dynamically changed by the interferometer’s internal *** calculate the joint-spectrum function and obtain the spectral-purity of photons and Schmidt number under different *** show that it is a dynamical method to adjust the spectral-purity and can optimize the spectralpurity of photons up to near 100%.The condition for high-spectral-purity photons is ensured by the micro-ring itself,so it overcomes the trade-off between spectral purity and brightness in the traditional post-filtering *** scheme is robust to fabrication variations and can be successfully applied in different fabrication labs and different *** high-spectral-purity photons will be beneficial for quantum information processing like Boson sampling and other quantum algorithms.

关键词： spectral-purity micro-ring Mach–Zehnder interferometer