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| 1 | Boosting the dimensionality of frequency entanglement using a reconfigurable microring resonator显示文摘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 processing.In 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 entanglement.We 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 calculations.In 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 PGR.In 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 number.This method is widely applicable to other material-based ring resonators and can act as a general solution for high-dimensional QFCs. | 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 | 2023 | Science China(Physics,Mechanics & Astronomy)2023，66，5： | 0 |
| 2 | On-chip multiphoton Greenberger-Horne Zeilinger state based on integrated frequency combs显示文摘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 computation.To 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 state.Here,we propose an ultra-integrated scalable on-chip GHZ state generation scheme based on frequency combs.By 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 mode.Both 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 wavelengths.In addition,we give the on-chip design of projection measurement for characterizing GHZ states and show the reconfigurability of the state.Our proposal is rather simple and feasible within the existing fabrication technologies and we believe it will boost the development of multiphoton technologies. | Pingyu Zhu Qilin Zheng Shichuan Xue Chao Wu Xinyao Yu Yang Wang Yingwen Liu Xiaogang Qiang Junjie Wu Ping Xu | 2020 | Frontiers of physics2020，15，6： | 0 |
| 3 | Experimental demonstration of quantum transport enhancement using time-reversal symmetry breaking on a silicon photonic chip显示文摘The continuous-time quantum walk is a basic model for studying quantum transport and developing quantum-enhanced algorithms. Recent studies show that by introducing a phase into the standard continuous-time quantum walk model, the time-reversal symmetry can be broken without changing the Hermitian property of the Hamiltonian. The time-reversal symmetry breaking quantum walk shows advantages in quantum transport, such as perfect state transfer, directional control, transport speedup, and quantum transport efficiency enhancement. In this work, we implement the time-reversal symmetry breaking quantum walks on a reconfigurable silicon photonic chip and demonstrate the enhancement introduced by breaking time-reversal symmetry. Perfect state transfer on a three-site ring, a quantum switch implemented on a six-site graph, and transport speedup using a linear chain of triangles are demonstrated with high fidelity. Time-reversal asymmetry has also been used in a simplified light-harvesting model,implying the potential of time-reversal symmetry breaking in photosynthesis investigations. | Yang Wang Xinyao Yu Shichuan Xue Yizhi Wang Junwei Zhan Chao Wu Pingyu Zhu Qilin Zheng Miaomiao Yu Yingwen Liu Xiaogang Qiang Junjie Wu Xuejun Yang Ping Xu | 2022 | Science China(Physics,Mechanics & Astronomy)2022，65，10： | 0 |
| 4 | Subrecoil cooling of ^(6)Li atoms by 2S→3P ultraviolet narrow transition显示文摘Laser cooling of atoms and molecules is crucial to exhibiting excellent features in the field of low-temperature physics.Cooling ^(6)Li atoms to very low temperatures is difficult due to their partially resolved D_(2) line of excited states.Here we report an observation of cooling ^(6)Li atom samples to 16μK with an ultraviolet(UV)laser in a magneto-optical trap,which breaks the Doppler cooling limit and approaches half of the photon-recoil limit.The essential mechanism of cooling results is that the natural linewidth is comparable to the recoil frequency in such a 2S→3P ultraviolet narrow transition.Laser frequency stability is important in the cooling process,and thus,the UV laser was locked to an optical frequency comb referenced to an ultrastable optical cavity.The cooling was numerically simulated to explain the cooling forces.The results can provide an ideal platform in the field of precision measurements and ultracold Fermi gases. | Yang Rui Liang Zhang Rui Li Pengyue Liu Xuemei Liu Chunyang Duan Shichuan Yu Yuelong Wu Haibin Wu | 2023 | Science China(Physics,Mechanics & Astronomy)2023，66，8： | 0 |
| 5 | Quantum algorithm and experimental demonstration for the subset sum problem显示文摘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. | Qilin ZHENG Pingyu ZHU Shichuan XUE Yang WANG Chao WU Xinyao YU Miaomiao YU Yingwen LIU Mingtang DENG Junjie WU Ping XU | 2022 | Science China(Information Sciences)2022，65，8： | 0 |
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