Advanced quantum technologies最新文献

Spin-orbit coupling (SOC) has broad relevances and its interplay with other interactions and potential geometry may induce novel quantum states. This work explores exotic quantum states emerging in the ground state (GS) of a strongly-correlated spin-1 Bose–Einstein condensate confined in 2D concentric annular traps with SOC. In the antiferromagnetic case, the GS density manifests various patterns of distributions, including facial-makeup states, petal states, topological fissure states, multiple-half-ring states and property-distinguished vertical and horizontal stripe states. A peculiar phenomenon of density-phase separation is noticed in the sense that the variations of density and phase tend to be independent. In ferromagnetic case, the GS exhibits a semi-circular or half-disk status of density embedded with vortices and antivortices. The spin distribution can self-arrange into an array of half-skyrmions and a half-antiskyrmion fence separating vortex-antivortex pairs is also found. This study indicates that one can manipulate the emergence of exotic quantum states and the locations of the topological defects via the interplay of the SOC, interactions and potential geometry and the abundant state variations might also provide potential resources for quantum metrology.

Dynamical phase transitions in the relaxation behavior of stochastic quantum walks are investigated, focusing on systems where coherent unitary evolution is periodically interrupted by dephasing. This interplay leads to a classicalization of the dynamics, effectively described by non-equilibrium Markovian processes that can violate detailed balance. As a result, such systems exhibit a richer and more complex spectral structure than their equilibrium counterparts. Extending recent insights from classical Markov dynamics [G. Teza et al., Phys. Rev. Lett. 130, 207103 (2023)], it is demonstrated that these quantum-classical hybrid systems can host not only first-order dynamical phase transitions – characterized by eigenvalue crossings – but also second-order transitions marked by the coalescence of eigenvalues and eigenvectors at exceptional points. Two paradigmatic models are analyzed: a quantum walk on a ring under gauge fields and a walk on a finite line with internal degrees of freedom, both exhibiting distinct mechanisms for breaking detailed balance. These findings reveal a novel class of critical behavior in open quantum systems, where decoherence-induced classicalization enables access to non-Hermitian spectral phenomena. Beyond their fundamental interest, these results offer promising implications for quantum technologies, including quantum simulation, error mitigation, and the engineering of controllable non-equilibrium quantum states.

A fiber inline compatible hybrid diamond cavity system manifesting Fano resonance in transmission, as well as emission spectra, is presented. This system comprises a 1D Bragg cavity structured elliptically faceted diamond nanowire coupled to an optical nanowire. The device exhibits ≈47% transmission variation within a wavelength range ≈522 pm with a moderate Q-factor ≈1100. The dual supermode-based photon coupling enables ≈80% photon coupling efficiency. The tunability of the Fano lineshape and the Purcell factor as high as 223 is attained by altering the dipole position of the quantum emitter. Such significantly high Purcell factor results in ≈150 times reduction in the decay time of quantum emitter emission, thereby allowing faster data transmission. It is believed that the proposed hybrid cavity Fano system may provide a new pathway for quantum optical switches, sensors, and applications at a single photon level.

Gate-based quantum computers are an innovative tool for experimentally studying the core principles of quantum mechanics. This work presents the first observation of quantum anomalous heat flow between two qubits and investigates the role of mid-circuit measurements in this context. Using mid-circuit measurements, we designed quantum circuits that violate the semi-classical heat flow bound, witnessing negativities in the underlying Kirkwood-Dirac quasiprobability distribution, which indicates the presence of quantum correlations between the subsystems. Mid-circuit measurements, crucial for probing qubits during the experiment, enabled these observations but also introduced disturbances, such as energy leakage, leading to deviations from theoretical predictions. These noise effects were modeled, providing insight into the limitations of current mid-circuit measurement techniques.

Non-binary (NB) low-density parity-check (LDPC) codes over high-order finite fields offer error-correction performance closer to the Shannon limit while directly processing NB symbols, making them well-suited for continuous-variable quantum key distribution (CV-QKD), which inherently involves high-dimensional data. However, current CV-QKD implementations have not been deeply researched in this area and still rely on binary error-correcting codes, limiting the full exploitation of continuous-variable information. Furthermore, the high sensitivity of CV-QKD to signal-to-noise ratio (SNR) fluctuations renders fixed-rate codes inadequate for practical channel variations. To address these issues, in this work an information reconciliation protocol is proposed based on rate-adaptive NB LDPC codes. It not only leverages the advantages of using LDPC codes over NB fields, but also exploits their ability to directly correct NB symbols by incorporating rate-adaptive techniques at both the symbol-wise and bit-wise granularity. Simulation results indicate that under identical conditions, reconciliation efficiency increases with field order, reaching 98.90% over Galois Field(GF)(64). In addition, both symbol-wise and bit-wise rate-adaptive techniques extend the applicability of fixed-rate NB LDPC codes, with the bit-wise scheme consistently yielding higher secure-key rates across all fields. Together, these techniques significantly enhance the efficiency and adaptability of CV-QKD information reconciliation.

The decoherence effect of the real quantum computer poses a significant challenge for designing quantum neural networks (QNN), which requires simultaneous consideration of model performances and parameterized quantum circuit (PQC) scales. In this paper, a method for the intelligent generation of lightweight QNN is proposed, which utilizes the parameters of quantum chips such as topology and relaxation time to assist the automatic design of QNNs. Combining the mixture expert mechanism with the Hyperband algorithm, a Mixture of Hyperband Experts for QNN is proposed to search for combinations of hyperparameters that meet multi-objective requirements from the lightweight QNN. To the best of the authors’ knowledge, this is the first work that combines quantum chip capabilities to intelligently generate lightweight QNNs. Experiments are carried out on datasets in the fields of medicine and information security, and compared with classical machine learning algorithms and quantum machine learning algorithms (QSVM, QKNN, Intelligent Generation for QNN), the QNN automatically generated by this method has good performance and scalability, and the PQC has a smaller scale. The anti-coherence capability of the QNN intelligently generated by this method is verified using experiments on a real quantum computer.

The notion of synthetic dimensions in artificial systems has received considerable attention as it provides novel methods for exploring hypothetical topological matter as well as potential device applications. A superconducting qutrit-resonator chain is mapped into domain-divided Su-Schrieffer–Heeger (SSH) models in the synthetic dimension formed by product states of qutrits and Fock states, which renders single-excitation transfers to mimic particle transports in 1D potential array. Large-scale Greenberger–Horne–Zeilinger (GHZ) states can be generated in one-domain SSH model of synthetic dimension via the topological protected edge channel. Uniquely, a two-domain SSH model is constructed, and the wave function of the three topological protected states is analytically derived. It is shown that the effective coherent-tunneling adiabatic passage (CTAP) enables fast large-scale GHZ state can be generated via topological CTAP. Furthermore, four- and multi-domain SSH models are identified to generate large-scale GHZ states faster in larger sizes. Numerical results show that topologically generated large-scale GHZ states exhibit excellent robustness against inevitable variation in ideal hopping rates and losses of systems. The work opens up prospects for realizing fast large-scale GHZ states in multiple SSH models of synthetic dimension and for facilitating further applications of topological matter in quantum information processing.

An efficient multiparty semi-quantum private comparison protocol based on Bell states is proposed. The proposed protocol enables the comparison of private information equality among multiple classical participants with the assistance of two semi-honest third parties. Unlike previous protocols, the proposed protocol can be further extended to resist the collective-dephasing noise and the collective-rotation noise, respectively. The proposed protocol and its extensions do not require the classical participants to generate and send new quantum states to the third party, and these participants can compare two privacies within one round of comparison. In addition, the protocol performs better with a qubit efficiency up to 25%. The security analysis indicates that the protocol is resilient to various known quantum attacks. Furthermore, the feasibility of this protocol is confirmed by simulation results on the IBM quantum platform.

It is shown theoretically how to use the EPR (electron paramagnetic resonance) technique, using electron spins as qubits, coupled with each other by the exchange interaction, to set the configuration of n qubits (n = 1–4) at resonance, in conjunction with pulses, to construct the NOT (one qubit), CNOT (two qubits), CCNOT (three qubits), and CCCNOT (four qubits) Toffoli gates, which can be exploited to build a quantum computer. This is unique to EPR, wherein exchange-coupled electron spins are used. This is different from NMR (Nuclear Magnetic Resonance), which uses nuclear spins as qubits, that do not couple with each other by the exchange interaction.

Entanglement is one of the most vital resources in quantum computing. Particularly, in quantum game theory, entanglement holds significant importance since it defines the interactions and the information exchange between two or more players. In this research work, a new set of entanglement operators is introduced for N-player quantum games. This study explores how their application affects each player's behavior throughout the game. Furthermore, the entangling capabilities are tested and evaluated for a wide range of entanglement operator angles, by exploiting the Von Neumann entropy metric, both on a simulator and on a real IBM Quantum system. Their hardware efficiency, against state-of-the-art quantum games entanglement operators, is assessed in terms of circuit depths and fidelity, and showcases their great potential as multiplayer quantum games operators. Finally, three methods are compared for computing the players’ payoffs, regarding their scalability and efficiency. This study shows that in all payoff cases, the quantum game results, computed by the quantum hardware, are in accordance with the simulated ones.