Advanced quantum technologies最新文献

Layout optimization problems involve finding the optimal arrangement of elements in order to maximize efficiency. For instance, the wind farm layout optimization (WFLO) problem consists of the best turbine placement to maximize energy production while minimizing wake losses. As its nonlinear and combinatorial nature makes it challenging for traditional optimization methods, alternative approaches such as quantum annealing and quantum-classical hybrid methods offer a promising alternative for tackling such complex problems. Here, WFLO is formulated as a Quadratic Unconstrained Binary Optimization (QUBO) problem using the Jensen wake model. A quantum annealer is compared, the Gurobi solver, and the Quantum Approximate Optimization Algorithm (QAOA). The quantum annealer provides solutions one order of magnitude faster than Gurobi with at most 3% lower power output, making it suitable for rapid suboptimal approximations. These findings highlight the trade-off between the quality of the solution and the computational time and demonstrate how quantum methods, especially when combined with classical solvers, can contribute to efficient renewable energy optimization.

A scheme is proposed to achieve ground state cooling in a dual-cavity optomechanical system. By solving the optimal coupling conditions in both red-detuned and blue-detuned regimes, it is demonstrated that ground state cooling is achievable over a wide range of parameters. The quantum interference effect induced by the cavity-cavity coupling plays a crucial role in suppressing the heating process and enhancing the cooling process, enabling ground state cooling of the mechanical resonator even in the blue-detuned regime. Furthermore, the SSH model is studied with next-nearest-neighbor (NNN) coupling and it is found that the NNN coupling not only induces the edge state but also enables ground state cooling of the mechanical resonator. The scheme provides new insights into the connection between optomechanical systems and topological models, paving the way for further exploration of their synergistic effects.

Achieving high-fidelity quantum teleportation requires the distribution of maximally entangled states through noiseless channels, a condition rarely met in practical implementations. In realistic environments, decoherence processes, such as amplitude damping, severely degrade entanglement quality. In this study, a universal strategy is proposed for protecting entanglement against amplitude damping noise by introducing escort qubits—ancillary qubits specifically designed to assist in the distribution process. This method involves CNOT operations and measurement of the escort qubits. Modeling the amplitude damping channel with a Lindblad master equation, it is showed analytically that the method achieves unit fidelity under ideal operations, independent of the damping rate, with a certain success probability. This method is applied to teleportation with Bell and W states, and compare its performance with weak measurement and environment-assisted measurement protocols. This approach offers superior fidelity, experimental feasibility, and independence from noise parameters, as confirmed through simulation and Qiskit implementation.

The polarization-entangled photon source (PEPS) at non-degenerated wavelengths is pivotal to connect quantum systems working at different wavelengths, with the assistance of quantum teleportation. Here, a compact Sagnac-type photon source is designed and demonstrated, in which two photons with wavelengths at 810 and 1550 nm are highly entangled in polarization degree of freedom. The two photons are generated from a periodically poled lithium niobate crystal pumped with a 532 nm continuous-wave laser, via type-0 nondegenerate spontaneous parametric down-conversion. The polarization of three lights is rotated by a single periscope, which makes the Sagnac interferometer compact and stable. The generated two photons are with high brightness of $��3�\times �{10}^4�$ pairs/s/mW, which are highly entangled with fidelity of $��0.985�\pm �0.002�$. The entanglement is verified by violating the Clauser-Horne-Shimony-Holt inequality with $��S�=�2.756�\pm �0.007�$. Finally, teleportation is demonstrated with this nondegenerate source, in which photonic states at 810 nm is teleported to 1550 nm with fidelity of $��0.955�\pm �0.003�$.

Testing for a violation of Bell-type inequalities provides a standard approach to investigating nonlocal correlations in nonclassical (entangled) states. In this study, a custom measurement operator composed of a linear combination of Pauli matrices ($�{\sigma }_x$, $�{\sigma }_y$, and $�{\sigma }_z$) is constructed to examine such violations. Both theoretical and experimental analyses of Bell-type inequality violations using two- and four-qubit Dicke states implemented on quantum computers are presented. Specifically, two methods for preparing four-qubit Dicke states—gate-based and statevector-based—are compared, and their performance is assessed on two IBM superconducting quantum processors, ibm_kyiv and ibm_sherbrooke. In the two-qubit scenario, a clear violation of the CHSH inequality is observed, with a maximum Bell parameter of $��2.821�\pm �0.0019�$ achieved using M3 error mitigation, closely approaching the theoretical upper bound of $��2�\sqrt{�2�}�$. For the four-qubit case, a Dicke-state-specific Bell-type inequality is applied and a maximal violation of $��2.607�\pm �0.029�$ is reported without additional mitigation using the statevector-based approach. These findings show that while error mitigation improves outcomes in gate-based methods, the statevector-based approach naturally provides higher fidelity with reduced noise. This work underscores the importance of state preparation strategies and noise management in exploring quantum correlations on current quantum computing platforms.

Multiparty-controlled joint remote state preparation (MCJRSP) enables multiple senders to jointly prepare an arbitrary state for a distant receiver via the control of multiple agents within a quantum network. The multipartite Greenberger–Horne–Zeilinger (GHZ) state is commonly employed as a key resource in MCJRSP protocols. However, the depth requirements of unitary circuits for GHZ state preparation and the unreliable long-distance distribution of GHZ states limit the practical applications of these MCJRSP tasks under current conditions. To overcome these limitations, a practical MCJRSP scheme is presented for remotely preparing arbitrary single-particle state without GHZ states. This scheme is further extended to remote preparation of arbitrary multi-particle state. The performance of the protocol is analyzed under certain types of noise, and compare it with existing GHZ-state-based protocols. The results indicate that the protocol exhibits superior robustness under noisy conditions when preparing multi-particle states. Moreover, it requires fewer quantum resources and does not necessitate classical communication. Additionally, the protocol offers a unique advantage: it can tolerate an arbitrary number of non-responsive agents. This study provides a more feasible and efficient approach for realizing MCJRSP in long-distance quantum communication networks.

A scheme for the fast detection of multi-period microwave (MW) pulses is proposed in a four-level Rydberg-atom system via electromagnetically induced transparency (EIT). Rydberg-atom EIT shows a transparency window with coupling of a probe and a control lasers. When the Rydberg atoms are irradiated by a MW field, the output pulse experiences serious time delay due to the medium dispersion. It is interesting to find that the time delay is much reduced when we use a relatively strong probe field. The simulation result indicates that the average time delay of the pulse series can be reduced to 0.32 $��\mu �s�$, which is about 1/8 of that in a single pulse detection. In this case, the nonlinear dispersion leads to fast detection of the pulse's wavefront. For the following pulses, the fast detection is attributed to the Kerr nonlinearity and atomic population dynamics. Moreover, its delay reduction ratio could reach up to 87.2%. The impacts of pulse durations, intervals, and thermal perturbations are also investigated and the scheme shows good robustness.

Deterministic sources of quantum light are becoming increasingly relevant in the development of quantum communication, particularly in deployed fiber networks. Therefore, efficient fiber-coupled sources at telecom wavelength are highly sought after. With this goal in mind, the fiber coupling performance of quantum dots is systematically investigated in optical resonators under three experimental configurations. For the first time coupling efficiency and sensitivity are quantified to spatial displacement for single-mode fibers with 3D printed optics on their tip, and benchmark their behavior over a commercial cleaved-cut fiber and a standard optical setup. The reduction of the required optical elements when operating with a lensed or a bare fiber allows for an increased end-to-end efficiency over a standard setup. For the perspective of realizing a mechanically stable fiber-coupled source, the spatial tolerance is precisely quantified to fiber-cavity misalignment, observing less than $��50��\%�$ count rate drop for several micrometers displacement. In the spirit of precise quantification and reproducibility, the experiments are performed on multiple photonic resonators. These results will play a key role in the future development of fiber-coupled sources of quantum light.

Hybrid quantum systems provide versatile physical properties that could be qualified for high-fidelity quantum information storage, distribution, and processing in a quantum network. This work proposes to synthesize a hybrid generalized Jaynes-Cummings (JC) model among two mircowave (MW) cavities and a Rydberg atom, where the Rydberg transition occurs by simultaneously absorbing or emitting two MW photons distributed in different cavities. Based on this synthesized Rydberg two-mode two-photon JC (TMTP-JC) model, a hybrid MW-MW-atom Toffoli gate is constructed with the atomic qubit encoded on two stable ground states. Furthermore, the Rydberg atom is considered as an interface in an MW-optical quantum network and a scheme is demonstrated for generating a three-body photonic entangled state among the two MW cavities and an optical cavity, assisted by the synthesized Rydberg TMTP-JC interaction. The proposed setup provides a Rydberg-state–mediated interface for constructing MW-MW-atom three-qubit gates and entangling three-body MW-MW-optical photons, which may bridge the gap for modular, scalable, and cross-platform quantum networks.

Nonreciprocal devices, such as isolator or circulator, are crucial for information routing and processing in quantum networks. Traditional nonreciprocal devices, which rely on the application of bias magnetic fields to break time-reversal symmetry and Lorentz reciprocity, tend to be bulky and require strong static magnetic fields. This makes them challenging to implement in highly integrated large-scale quantum networks. Therefore, a multifunctional nonreciprocal quantum device based on the integration and tunable interaction of superconducting quantum circuit (SQC) is designed. This device can switch between two-port isolator, three-port symmetric circulator, and antisymmetric circulator under the control of external magnetic flux. Furthermore, both isolator and circulator can achieve nearly perfect unidirectional signal transmission. It is believed that this scalable and integrable nonreciprocal device can provide new insight for the development of large-scale quantum networks.