查看更多>>摘要：We investigate the higher-order topological laser in the two-dimensional(2D)coupled-cavity array.By adding stag-gered on-site gain and loss to the 2D Hermitian array with a trivial phase,the system will emerge degenerate topological corner modes,which are protected by bulk band gap.For such a non-Hermitian model,by adjusting the parameters of the system and introducing the pumping into the cavity at the corner,a single-mode lasing with topological protection emerges.Furthermore,single-mode lasing exists over a wide range of pumping strengths.No matter where the cavity is initially stimulated,after enough time evolution,all the cavities belonging to the topological corner mode can emit a stable laser.
查看更多>>摘要：Optical mode converters are essential for enhancing the capacity of optical communication systems.However,fabrica-tion errors restrict the further improvement of conventional mode converters.To address this challenge,we have designed an on-chip TE0-TE1 mode converter based on topologically protected waveguide arrays.The simulation results demonstrate that the converter exhibits a mode coupling efficiency of 93.5％near 1550 nm and can tolerate a relative fabrication error of 30％.Our design approach can be extended to enhance the robustness for other integrated photonic devices,beneficial for future development of optical network systems.
查看更多>>摘要：To conveniently calculate the Wigner function of the optical cumulant operator and its dissipation evolution in a thermal environment,in this paper,the thermo-entangled state representation is introduced to derive the general evolution formula of the Wigner function,and its relation to Weyl correspondence is also discussed.The method of integration within the ordered product of operators is essential to our discussion.
查看更多>>摘要：We study the exceptional-point(EP)structure and the associated quantum dynamics in a system consisting of a non-Hermitian qubit and a Hermitian qubit.We find that the system possesses two sets of EPs,which divide the system-parameter space into PT-symmetry unbroken,partially broken and fully broken regimes,each with distinct quantum-dynamics characteristics.Particularly,in the partially broken regime,while the PT-symmetry is generally broken in the whole four-dimensional Hilbert space,it is preserved in a two-dimensional subspace such that the quantum dynamics in the subspace are similar to those in the PT-symmetry unbroken regime.In addition,we reveal that the competition between the inter-qubit coupling and the intra-qubit driving gives rise to a complex pattern in the EP variation with system parameters.
查看更多>>摘要：In some schemes,quantum blind signatures require the use of difficult-to-prepare multiparticle entangled states.By considering the communication overhead,quantum operation complexity,verification efficiency and other relevant factors in practical situations,this article proposes a non-entangled quantum blind signature scheme based on dense encoding.The information owner utilizes dense encoding and hash functions to blind the information while reducing the use of quantum resources.After receiving particles,the signer encrypts the message using a one-way function and performs a Hadamard gate operation on the selected single photon to generate the signature.Then the verifier performs a Hadamard gate inverse operation on the signature and combines it with the encoding rules to restore the message and complete the verification.Compared with some typical quantum blind signature protocols,this protocol has strong blindness in privacy protection,and higher flexibility in scalability and application.The signer can adjust the signature operation according to the actual situation,which greatly simplifies the complexity of the signature.By simultaneously utilizing the secondary distribution and rearrangement of non-entangled quantum states,a non-entangled quantum state representation of three bits of classical information is achieved,reducing the use of a large amount of quantum resources and lowering implementation costs.This improves both signature verification efficiency and communication efficiency while,at the same time,this scheme meets the requirements of unforgeability,non-repudiation,and prevention of information leakage.
查看更多>>摘要：We redesign the parameterized quantum circuit in the quantum deep neural network,construct a three-layer structure as the hidden layer,and then use classical optimization algorithms to train the parameterized quantum circuit,thereby propose a novel hybrid quantum deep neural network(HQDNN)used for image classification.After bilinear interpolation reduces the original image to a suitable size,an improved novel enhanced quantum representation(INEQR)is used to encode it into quantum states as the input of the HQDNN.Multi-layer parameterized quantum circuits are used as the main structure to implement feature extraction and classification.The output results of parameterized quantum circuits are converted into classical data through quantum measurements and then optimized on a classical computer.To verify the performance of the HQDNN,we conduct binary classification and three classification experiments on the MNIST(Modified National Institute of Standards and Technology)data set.In the first binary classification,the accuracy of 0 and 4 exceeds 98％.Then we compare the performance of three classification with other algorithms,the results on two datasets show that the classification accuracy is higher than that of quantum deep neural network and general quantum convolutional neural network.
查看更多>>摘要：Topological insulators occupy a prominent position in the realm of condensed matter physics.Nevertheless,the pres-ence of strong disorder has the potential to disrupt the integrity of topological states,leading to the localization of all states.This study delves into the intricate interplay between topology and localization within the one-dimensional Su-Schrieffer-Heeger(SSH)model,which incorporates controllable off-diagonal quasi-periodic modulations on superconducting circuits.Through the application of external alternating current(ac)magnetic fluxes,each transmon undergoes controlled driving,enabling independent tuning of all coupling strengths.Within a framework of this model,we construct comprehensive phase diagrams delineating regions characterized by extended topologically nontrivial states,critical localization,and co-existing topological and critical localization phases.The paper also addresses the dynamics of qubit excitations,elucidating distinct quantum state transfers resulting from the intricate interplay between topology and localization.Additionally,we propose a method for detecting diverse quantum phases utilizing existing experimental setups.
查看更多>>摘要：Valley,the intrinsic feature of silicon,is an inescapable subject in silicon-based quantum computing.At the spin-valley hotspot,both Rabi frequency and state relaxation rate are significantly enhanced.With protection against charge noise,the valley degree of freedom is also conceived to encode a qubit to realize noise-resistant quantum computing.Here,based on the spin qubit composed of one or three electrons,we characterize the intrinsic properties of valley in an isotopically enriched silicon quantum dot(QD)device.For one-electron qubit,we measure two electric-dipole spin resonance(EDSR)signals which are attributed to partial occupation of two valley states.The resonance frequencies of two EDSR signals have opposite electric field dependences.Moreover,we characterize the electric field dependence of the upper valley state based on three-electron qubit experiments.The difference of electric field dependences of the two valleys is 52.02 MHz/V,which is beneficial for tuning qubit frequency to meet different experimental requirements.As an extension of electrical control spin qubits,the opposite electric field dependence is crucial for qubit addressability,individual single-qubit control and two-qubit gate approaches in scalable quantum computing.
查看更多>>摘要：Nonlinearly induced steady-state photon-phonon entanglement of a dissipative coupled system is studied in the bistable regime.Quantum dynamical characteristics are analysed by solving the mean-field and fluctuation equations of the system.It is shown that dissipative coupling can induce bistable behaviour for the effective dissipation of the system.Under suitable parameters,one of the steady states significantly reduces the dissipative effect of the system.Consequently,a larger steady-state entanglement can be achieved compared to linear dynamics.Furthermore,the experimental feasibility of the parameters is analysed.Our results provide a new perspective for the implementation of steady-state optomechanical entanglement.
查看更多>>摘要：Quantum error correction,a technique that relies on the principle of redundancy to encode logical information into additional qubits to better protect the system from noise,is necessary to design a viable quantum computer.For this new topological stabilizer code-XYZ2 code defined on the cellular lattice,it is implemented on a hexagonal lattice of qubits and it encodes the logical qubits with the help of stabilizer measurements of weight six and weight two.However topological stabilizer codes in cellular lattice quantum systems suffer from the detrimental effects of noise due to interaction with the environment.Several decoding approaches have been proposed to address this problem.Here,we propose the use of a state-attention based reinforcement learning decoder to decode XYZ2 codes,which enables the decoder to more accurately focus on the information related to the current decoding position,and the error correction accuracy of our reinforcement learning decoder model under the optimisation conditions can reach 83.27％under the depolarizing noise model,and we have measured thresholds of 0.18856 and 0.19043 for XXYZ2 codes at code spacing of 3-7 and 7-11,respectively.our study provides directions and ideas for applications of decoding schemes combining reinforcement learning attention mechanisms to other topological quantum error-correcting codes.
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