Advanced quantum technologies最新文献

The notion of $��s�u�\left(�2�\right)�$ spin-$�s$ Dicke states is introduced, which are higher-spin generalizations of usual (spin-1/2) Dicke states. These multi-qudit states can be expressed as superpositions of $��s�u�(�2�s�+�1�)�$ qudit Dicke states. They satisfy a recursion formula, which is used to formulate an efficient quantum circuit for their preparation, whose size scales as $��s�k�(�2�s�n�-�k�)�$, where $�n$ is the number of qudits and $�k$ is the number of times the total spin-lowering operator is applied to the highest-weight state. The algorithm is deterministic and does not require ancillary qudits.

This tutorial introduces a systematic approach for addressing the key question of quantum metrology: For a generic task of sensing an unknown parameter, what is the ultimate precision given a constrained set of admissible strategies. The approach outputs the maximal attainable precision (in terms of the maximum of quantum Fisher information) as a semidefinite program and optimal strategies as feasible solutions thereof. Remarkably, the approach can identify the optimal precision for different sets of strategies, including parallel, sequential, quantum SWITCH-enhanced, causally superposed, and generic indefinite-causal-order strategies. The tutorial consists of a pedagogic introduction to the background and mathematical tools of optimal quantum metrology, a detailed derivation of the main approach, and various concrete examples. As shown in the tutorial, applications of the approach include, but are not limited to, strict hierarchy of strategies in noisy quantum metrology, memory effect in non-Markovian metrology, and designing optimal strategies. Compared with traditional approaches, the approach here yields the exact value of the optimal precision, offering more accurate criteria for experiments and practical applications. It also allows for the comparison between conventional strategies and the recently discovered causally-indefinite strategies, serving as a powerful tool for exploring this new area of quantum metrology.

Source-independent quantum random number generators (SI-QRNGs) can generate secure random numbers with untrusted and uncharacterized sources. Recently, a tomography-based SI-QRNG protocol has garnered significant attention for its higher randomness generation rate[Phys. Rev. A 99, 022328 (2019)], achieved through measurements utilizing three mutually unbiased bases. However, imperfect and inadequately characterized measurement devices would impact the security and performance of this protocol. In this work, considering the imperfect basis modulation, afterpulse effect and detection efficiency mismatch, it is demonstrated that the imperfect measurement devices would reduce the extractable randomness and lead to the incorrect estimation of the conditional min-entropy. Additionally, the influences of the finite-size effect and the performances of the protocol based on different parameter estimation methods are investigated and compared. To guarantee the security of generated random numbers, accurate conditional min-entropy estimation methods that are compatible with imperfect factors are also developed. The work emphasizes the significance of considering the imperfections in measurement devices and establishing tighter bounds for parameter estimation, especially in high-speed systems, thereby enhancing the robustness and performance of the protocol.

Entropic dynamics of a multiqubit cavity quantum electrodynamics system is simulated and various aspects of entropy are explored. In the modified version of the Tavis–Cummings–Hubbard model, atoms are held in optical cavities through optical tweezers and can jump between different cavities through the tunneling effect. The interaction of atom with the cavity results in different electronic transitions and the creation and annihilation of corresponding types of photon. Electron spin and the Pauli exclusion principle are considered. Formation and break of covalent bond and creation and annihilation of phonon are also introduced into the model. The system is bipartite. The effect of all kinds of interactions on entropy is studied. And the von Neumann entropy of different subsystems is compared. The results show that the entropic dynamics can be controlled by selectively choosing system parameters, and the entropy values of different subsystems satisfy certain inequality relationships.

Anonymous secret sharing (ASS) is an essential cryptographic concept that facilitates the sharing and reconstruction of secret information while safeguarding the identity of the involved secret receivers, which has broad applications in key management, data backup, and distributed systems. In this study, a novel authenticated quantum anonymous secret sharing (QASS) protocol that emphasizes information privacy and identity anonymity protection is proposed. Employing $�d$-level multipartite GHZ states as a quantum resource, one-sided anonymous entanglement (AE) is innovatively established between the dealer and anonymous receivers, enabling the dealer to distribute a random share of secret information. Additionally, by establishing a one-sided AE between anonymous receivers and restorer, the restorer can securely collect and reconstruct the secret information using quantum teleportation (QT). Rigorous security analysis demonstrates that protocol can resist attacks from active adversaries and potentially dishonest users. Quantum experiments on IBM Qiskit validate the correctness and feasibility of the proposed QASS protocol. This work contributes to the advancement of quantum anonymous communication, addressing the requirements for information privacy and identity anonymity in practical application environments.

Quantum technologies are advancing from fundamental research in specialized laboratories to practical applications in the field, driving the demand for robust, scalable, and reproducible system integration techniques. Ceramic components can be pivotal thanks to high stiffness, low thermal expansion, and excellent dimensional stability under thermal stress. Lithography-based additive manufacturing of technical ceramics is explored, especially for miniaturized physics packages and electro-optical systems. This approach enables functional systems with precisely manufactured, intricate structures, and high mechanical stability while minimizing size and weight. It facilitates rapid prototyping, simplifies fabrication and leads to highly integrated, reliable devices. As an electrical insulator with low outgassing and high temperature stability, printed technical ceramics such as $��{\mathrm{Al}}_2�O_3�$ and AlN bridge a technology gap in quantum technology and offer advantages over other printable materials. This potential is demonstrated with CerAMRef, a micro-integrated rubidium D2 line optical frequency reference on a printed $��{\mathrm{Al}}_2�O�{}_3�$ micro-optical bench and housing. The frequency instability of the reference is comparable to laboratory setups while the volume of the integrated spectroscopy setup is only $��6��m�L�$. Potential for future applications is identified in compact atomic magnetometers, miniaturized optical atom traps, and vacuum system integration.

This research investigates the unconventional photon blockade in a hybrid optomechanical system with an embedded spin-triplet state. The self-homodyning interference between squeezed quantum fluctuations produced by the emitter and the coherent fraction from the driving laser results in two-photon suppression. Analytical solutions of the correlator equation and numerical simulations of the master equation reveal that modulated mechanical dissipation plays a crucial role in achieving strong single-photon blockade. In contrast to conventional cavity optomechanical systems, a second-order correlation function of $��g^{�\left(�2�\right)�}��\left(�0�\right)��\simeq �0�$ can be achieved with weak single-photon optomechanical coupling. By combining unconventional and conventional antibunching, the hybrid system achieves the convergence of maximal photon population, two-photon interference, and suppression of higher-order correlations. Additionally, the influence of the thermal noise on photon blockade is investigated, demonstrating greater robustness of the second-order correlation under weaker phonon-spin coupling.

Temperature sensing at the nanoscale is a significant experimental challenge. Here, an approach using dressed states is reported to make a leading quantum sensor – the nitrogen-vacancy (NV) center in diamond – selectively sensitive to temperature, even in the presence of normally confounding magnetic fields. Using an experimentally straightforward approach, the magnetic sensitivity of the NV center is suppressed by a factor of seven, while retaining full temperature sensitivity and narrowing the NV center linewidth. These results demonstrate the power of engineering the sensor Hamiltonian using external control fields to enable sensing with improved specificity to target signals.

Quantum error mitigation aims to reduce errors in quantum systems and improve accuracy. Zero-noise extrapolation (ZNE) is a commonly used method, where noise is amplified, and the target expectation is extrapolated to a noise-free point. However, ZNE relies on assumptions about error rates based on the error model. In this study, a purity-assisted zero-noise extrapolation (pZNE) method is utilized to address limitations in error rate assumptions and enhance the extrapolation process. The pZNE is based on the Pauli diagonal error model implemented using the Pauli twirling technique. Although this method does not significantly reduce the bias of routine ZNE, it extends its effectiveness to a wider range of error rates where routine ZNE may face limitations. In addition, the practicality of the pZNE method is verified through numerical simulations and experiments on the online quantum computation platform, Quafu. Comparisons with routine ZNE and virtual distillation methods show that biases in extrapolation methods increase with error rates and may become divergent at high error rates. The bias of pZNE is slightly lower than routine ZNE, while its error rate threshold surpasses that of routine ZNE. Furthermore, for full density matrix information, the pZNE method is more efficient than the routine ZNE.