Advanced quantum technologies最新文献

In the realm of fundamental quantum science and technologies, non-classical states of light, such as single-photon Fock states, are widely studied. However, current standards and metrological procedures are not optimized for low light levels. Progress in this crucial scientific domain depends on innovative metrology approaches, utilizing reliable devices based on quantum effects. A new generation of molecule-based single-photon sources is presented, combining their integration in a polymeric micro-lens with pulsed excitation schemes, thereby realizing suitable resources in quantum radiometry. The strategy enhances the efficiency of generated single photon pulses and improves stability, providing a portable source at 784.7 nm that maintains consistent performance even through a cooling and heating cycle. The calibration of a single-photon avalanche detector is demonstrated using light sources with different photon statistics, and the advantages of the single-molecule device are discussed. A relative uncertainty on the intrinsic detection efficiency well below 1% is attained, representing a new benchmark in the field.

Two cavity-magnon subsystems coupled via the two single-mode cavities mediated by a non-degenerate parametric down conversion and each cavity carrying a magnon confined in a Yttrium-iron-garnet sphere is proposed to study one-way quantum steering and asymmetric tripartite entanglement. The entanglement can be transferred from the two microwave cavities to the two separated magnon modes using magnetic dipole interaction. Different from previous schemes, the present study demonstrates efficient realization of controllable one-way quantum steering between two magnon modes through asymmetric frequency detunings of the two magnon modes. In addition, an asymmetric tripartite entanglement can also be achieved. Furthermore, the system exhibits robustness to temperatures up to 100 mK, providing a promising avenue for utilizing cavity magnonics systems in unidirectional transmission of quantum information.

Light-matter interactions provide an ideal testground for interplay of critical phenomena, topological transitions, quantum metrology, and non-Hermitian physics with high controllability and tunability. The present work considers two fundamental non-Hermitian Jaynes-Cummings models in light-matter interactions that possess real energy spectra in parity-time (PT) symmetry and anti-PT symmetry. The quantum Fisher information is shown to be critical around the transitions at the exceptional points and exhibit a super universality, with respect to different parameters, all energy levels, both models, symmetric phases, and symmetry-broken phases, which guarantees a universally high measurement precision in quantum metrology. In particular, the transitions are found to be both symmetry-breaking Landau-class transitions (LCTs) and symmetry-protected topological-class transitions (TCTs), thus realizing a simultaneous occurrence of critical LCTs and TCTs that are conventionally incompatible due to contrary symmetry requirements. Besides establishing a paradigmatic case to break the incompatibility of the LCTs and the TCTs in non-Hermitian systems, the both availabilities of the sensitive critical feature and the robust topological feature can also provide more potential for designing quantum devices or sensors.

This work presents an innovative approach for measuring the spin polarizations of coupled atomic ensembles in spin-exchange relaxation-free (SERF) comagnetometers, using the phase-frequency response of the magnetic field. The zero-phase point in the phase-frequency response of the magnetic field along the $�y$-axis is examined to determine the deceleration factor and electronic magnetic field. Ultimately, the spin polarizations of electrons and noble-gas atoms are calculated. The method is applied to test vapor cells with different parameters under various temperatures and pumping light intensities. The measurement errors caused by transverse electron relaxation of electronic spin polarization and nuclear spin polarization are $�\approx$5.59% and 1.95% under high polarization, and 8.06% and 2.62% under low polarization. The measurement method features minimal impact on nuclear spin polarization and wide applicability compared to other methods, making it more applicable and suitable for SERF comagnetometers. This method has great significance in better understanding the system state of the SERF comagnetometer and improving its sensitivity.

Deutsch's algorithm is the first quantum algorithm to demonstrate an advantage over classical algorithms. Here, Deutsch's problem is generalized to $�n$ functions and a quantum algorithm with an indefinite causal order is proposed to solve this problem. The algorithm not only reduces the number of queries to the black box by half compared to the classical algorithm, but also significantly decreases the complexity of the quantum circuit and the number of required quantum gates compared to the generalized Deutsch's algorithm. The algorithm is experimentally demonstrated in a stable Sagnac loop interferometer with a common path, which overcomes the obstacles of both phase instability and low fidelity of the Mach–Zehnder interferometer. The experimental results show both ultrahigh and robust success probabilities $��\approx ��99.7��\%�$. This study opens a path toward solving practical problems with indefinite cause-order quantum circuits.

Quantum Machine Learning (QML) leverages the transformative power of quantum computing to explore a broad range of applications, including optimization, data analysis, and complex problem-solving. Central to this study is the using of an innovative intrusion detection system leveraging QML models, with a preference for Quantum Neural Network (QNN) architectures for classification tasks. The inherent advantages of QNNs, notably their parallel processing capabilities facilitated by quantum computers and the exploitation of quantum superposition and parallelism, are elucidated. These attributes empower QNNs to execute certain classification tasks expediently and with heightened efficiency. Empirical validation is conducted through the deployment and testing of a QNN-based intrusion detection system, employing a subset of the CIC-DDoS 2019 dataset. Notably, despite employing a reduced feature set, the QNN-based system exhibits remarkable classification accuracy, achieving a commendable rate of 92.63%. Moreover, the study advocates for the utilization of quantum computing libraries such as Qiskit, facilitating QNN training on local machines or quantum simulators. The findings underscore the efficacy of a QNN-based intrusion detection system in attaining superior classification accuracy when confronted with large-scale training datasets. However, it is imperative to acknowledge the constraints imposed by the limited number of qubits available on local machines and simulators.

QSimon algorithm (a full quantum version of Simon's algorithm) is used to find periods in commitment functions and does not require classical calculations. However, QSimon algorithm circuit is incomplete, and the implementation of an essential component (solving boolean linear equations) has high resource consumption. This work further studies QSimon algorithm and applies QSimon algorithm to attack the offset two-round (OTR) scheme. QSimon algorithm is established by quantum boolean linear equations solving algorithm and general quantum truncation technique, which can obtain the period of any truncated function with overwhelming probability. The confidentiality and integrity of the OTR scheme are compromised by employing QSimon algorithm. The attacks ensure a high success rate and realize exponential speedup compared with classical versions.

A cyclic four-mode optical system is investigated with anti-parity-time symmetry. The energy spectra is analyzed and reveal the topological phase transition under different parameter regimes. In the topological phase regions, it is found that the degree of localization of the edge states can be tuned by modulating the vertical hopping strength. Moreover, it is observed that the emergence of nonzero energy edge states and the expansion of the topological phase regions. Meanwhile, it is found that the nonzero energy edge states still adhere to the bulk boundary correspondence, and which can be demonstrated by the bulk bandgap. Zero and nonzero energy edge states are also characterized by Zak phase and hidden Chern number. These results enrich the study of topological phases and edge states in non-Hermitian optical systems.