Advanced quantum technologies最新文献

Quantum state transfer is the act of transferring quantum information from one system in a quantum network to another without physically transporting carriers of quantum information, but instead engineering a Hamiltonian such that the state of the sender is transferred to the receiver through the dynamics of the whole network. A generalization of quantum state transfer called quantum routing concerns simultaneous transfers between multiple pairs in a quantum network, imposing limitations on its structure. This study considers transfer of Gaussian states over noisy quantum networks with modular structure, which have been identified as a suitable platform for quantum routing. Two noise models are compared, affecting either the network topology or the network constituents, studying their effects on both the transfer fidelities and the network properties. The two models are found to affect different features of the network allowing for the identification and quantification of the noise. These features are then used as a guide toward different strategies for the compensation of the noise, and to examine how the compensation strategies perform. The results show that in general, modular networks are more robust to noise than monolithic ones.

This short review provides an overview of some aspects of the current understanding of Mott insulators and Mott metal-insulator transitions. The development of this field is traced, from earliest classical views to the state-of-the-art picture based on methods of quantum field theory. A quasi-local view point, characterizing “pure” Mott physics, throughout this article is focused on. Following an extensive discussion on Mott transitions in one- and multi-orbital Hubbard models, progress is reviewed in first-principles correlation-based approaches in achieving a quantitative description of insulator-metal transitions in two celebrated Mott materials. Building thereupon, success of such approaches in providing microscopic justification for the famed Mott criterion, as well as in the attempts to model emerging devices is reviewed briefly. The study is concluded with a discussion of a class of Mott insulators modeled by the Kugel-Khomskii model, and discuss how progress in the understanding of novel quantum liquid-crystal-like order provides an attractive opportunity to gain insight into topologically ordered states and topological-to-trivial phase transitions for certain quantum spin models in terms of a dual description in terms of Landau-like symmetry breaking.

The unit commitment problem (UCP) is a non-convex mixed-integer programming issue that is crucial in the power system. The quantum alternating direction method of multipliers (QADMM) decompose the UCP into quadratic binary optimization (QBO) subproblems and continuous optimization subproblems. Relaxing constraints reformulate the QBO into a quadratic unconstrainted binary optimization (QUBO) problem, which can be addressed using quantum algorithms. Nevertheless, this approach lacks precision for hard constraints and requires more qubits, limiting the UCP scale addressed within QADMM. To confront the aforementioned challenges, this study introduces the consensus constraint-encoded divide-and-conquer QADMM (CCDC-QADMM). As a scalable fully distributed algorithm, CCDC-QADMM decomposes the UCP into two subproblems: Subproblem 1, a QUBO problem embedded with minimum up/down constraints, and Subproblem 2, a UC problem without minimum up/down constraints. By employing variable duplication for decoupling and leveraging the principles of average consensus, CCDC-QADMM achieves fully distributed computation. Specifically, in the QUBO subproblem 1, this algorithm encodes minimum up/down constraints into a hard constraint form within the mixing Hamiltonian. Simultaneously, it employs a divide-and-conquer strategy to accommodate the current constraints posed by the limited qubit resources. The effectiveness and scalability of this algorithm are substantiated through practical validation within real-world UCP scenarios.

Fluorescence spectra of nanodiamonds synthesized at high pressure from adamantane and other organic compounds show narrow (≈1 nm) lines of unknown origin over the spectroscopic range from ≈500 to 800 nm. The study proposes and experimentally confirms the hypothesis that these lines are related to radiative recombination of donor–acceptor pairs (DAP). According to the experimental data, these pairs can be formed from donor-like substitutional nitrogen present in the diamond lattice and 2D acceptor layer resulting from the effect of transfer doping on the nanodiamond surface. A peculiar behavior of the narrow lines is identified within the temperature range of 100–10 K: their energy position slightly shifts downward, and the majority of the lines divide into two or more components as the temperature decreases. The lines are shown to be predominantly associated with single photon emitters, with an emission rate exceeding 1 million counts s⁻¹ at room temperature. A new narrowband source of room-temperature fluorescence found in hydrogen-terminated nanodiamonds push horizons for quantum optical technologies related to the development of single photon emitters and temperature nanosensors.

Successfully implementing a quantum algorithm involves maintaining a low logical error rate by ensuring the validity of the quantum fault-tolerance theorem. The required number of physical qubits arranged in an array depends on the chosen Quantum Error Correction code and the achievable physical qubit error rate. As the qubit count in the array increases, parallel gating —simultaneously manipulating many qubits— becomes a crucial ingredient for successful computation. In this study, small arrays of a type of donor- and quantum dot-based qubits, known as flip-flop (FF) qubits, are investigated. Simulation results of gate fidelities in linear, square and star arrays of four FF qubits affected by realistic 1/f noise are presented to study the effect of parallel gating. The impact of two, three and four parallel one-qubit gates, as well as two parallel two-qubit gates, on fidelity is calculated by comparing different array geometries. The findings can contribute to the optimized manipulation of small FF qubit arrays and the design of larger ones.

In the rapidly evolving field of quantum information technology, the accurate and efficient classification of single-photon emitters is paramount. Traditional methods, which rely on conducting time-intensive Hanbury Brown-Twiss (HBT) experiments to acquire the 2nd-order correlation function of photon statistics, are not efficient. This study presents a pioneering solution that employs Deep Convolutional Neural Networks (CNNs) to classify single-photon emitters in confocal fluorescence microscope images, thereby bypassing the need for laborious HBT experiments. Focusing on the nitrogen-vacancy centers in diamond, the model is trained using fluorescence images of emitters that have been previously classified through HBT experiments. Applied to unclassified fluorescence images, the model achieves up to 98% accuracy in classification, substantially accelerating the identification process. This advancement not only makes the classification workflow more efficient but also promises wider applicability across various color centers and isolated atomic systems that necessitate imaging for isolation verification. This research signifies a substantial advancement in the application of quantum technologies, leveraging the power of deep learning to optimize the utilization of single-photon emitters.

The magnomechanical interaction arises from the coupling between magnons and phonons, an effect that has attracted significant attention. Leveraging this foundation, an ultralow threshold phonon laser within a parity-time ($�\mathrm{PT}$)-symmetric cavity magnomechanical (CMM) system is investigated. The $�\mathrm{PT}$-symmetry is achieved by incorporating a gain mechanism into the cavity mode and the amplification of phonon excitation number is achieved through the pumping of magnon mode. As the gain and dissipation approach the equilibrium, the mechanical gain undergoes a notable amplification, giving rise to a phonon laser action characterized by an ultralow threshold condition. This finding not only promotes a cross-disciplinary approach in fields such as non-Hermitian physics and quantum magnomechanics but also points to a promising path for enhancing the magnomechanical effect.

Rydberg atom arrays operated by a quantum adiabatic principle are among the most promising quantum simulating platforms due to their scalability and long coherence time. From the perspective of combinatorial optimization, they offer an efficient solution for an intrinsic maximum independent set problem because of the resemblance between the Rydberg Hamiltonian and the cost function of the maximum independent set problem. In this study, a strategy is suggested to approximate maximum independent sets by adjusting local detunings on the Rydberg Hamiltonian according to each vertex's vertex support, which is a quantity that represents connectivity between vertices. By doing so, the strategy successfully reduces the error rate three times for the checkerboard graphs with defects when the adiabaticity is sufficient. In addition, the strategy decreases the error rate for random graphs even when the adiabaticity is relatively insufficient. Moreover, it is shown that the strategy helps to prepare a quantum many-body ground state by raising the fidelity between the evolved quantum state and a 2D cat state on a square lattice. Finally, the strategy is combined with the non-abelian adiabatic mixing and this approach is highly successful in finding maximum independent sets compared to the conventional adiabatic evolution with local detunings.

Spatial distribution-controlled single-photon emitters operating is demonstrated in telecom wavelength range at room-temperature with GaN thin film grown on a patterned sapphire substrate (PSSs) with varying pattern sizes and dimensions. The analysis focuses on the various optical properties of defects within the GaN thin film, particularly their interactions with PSS. The confocal fluorescence mapping at room temperature revealed localized single-photon emitters inside the GaN layers located between the patterns. In addition, compared to conventional sapphire substrates, PSS can scatter photons outside the total reflection cone, thereby enhancing the light extraction efficiency. From the samples, the single photon emission is observed in the telecom wavelength ranging from 1.1 to 1.35 µm at room temperature, which is critical for advancing quantum communication technologies, and elucidate how the physical characteristics of PSS influence the performance and efficiency of GaN-based single-photon emitters.

Ever since the discussions about a possible quantum computer arised, quantum simulations have been at the forefront of possible utilities, with the task of quantum simulations being one that promises quantum advantage. Recently, advancements have made it feasible to simulate complex molecules using Variational Quantum Eigensolvers or study the dynamics of many-body spin Hamiltonians. These simulations have the potential to yield valuable outcomes through the application of error mitigation techniques. Simulating smaller models carries a great amount of importance as well and currently, in the Noisy Intermediate Scale Quantum era, is more feasible since it is less prone to errors. The objective of this work is to examine the theoretical background and the circuit implementation of a quantum tunneling simulation, with an emphasis on hardware considerations. This study presents the theoretical background required for such implementation and highlights the main stages of its development. By building on classic approaches of quantum tunneling simulations, this study aims at improving the result of such simulations by employing error mitigation techniques, Zero Noise Extrapolation, and Readout Error Mitigation and uses them in conjunction with multiprogramming of the quantum chip, a technique used for solving the hardware under-utilization problem that arises in such contexts.