Advanced quantum technologies最新文献

Secure multiparty quantum summation, as a critical part of secure multiparty quantum computation, plays a pivotal role in the field of quantum cryptography. In this paper, a hybrid protocol is proposed to implement secure multiparty quantum summation and anonymous ranking simultaneously, which uses $�d$-level two-particle entangled states. In the designed protocol, the particles are conveyed in the way of the circle-type transmission mode, which can compute the sum of the secret and the ranking by analyzing the distribution of participants associated with different secret values. Moreover, random number sequences can be obtained by constructing a fundamental system of solutions, which avoids the transmission of random numbers and reduces the use of quantum resources. According to the analysis, it can be seen that the protocol is secure against known attacks, and the secrets remain undisclosed throughout the protocol's implementation.

Nonlinear interferometers are a ubiquitous tool in quantum photonics. As such, they allow spooky-like imaging with undetected light. On the one side their working principle is based on the principle of induced coherence, which is deeply rooted in the heart of quantum mechanics. On the other side, they bear the strong potential to serve as new tool for biomedical imaging. In this review, an extensive overview about nonlinear interferometers and their working principle is given. A particular focus is set on their exploitation for quantum imaging and sensing. In addition, related side topics and further application fields as well as perspectives are provided.

Thermodynamics as a fundamental branch of physics examines the relationships between heat, work, and energy. The maximum energy extraction can be characterized by using the passive states that have no extracted energy under any cyclic unitary process. In this paper, the focus is on the concept of marginal passive state energy and derive polygon inequalities for multi-qubit entangled pure states. It is shown that the marginal passive state energies collectively form a convex polytope for each class of quantum states that are equivalent under SLOCC. Multipartite passive state energy criteria is introduced to classify multipartite entanglement under SLOCC. The present result provides a thermodynamic method to witness multipartite entanglement.

The impact of noise sources in real-world implementations of twin-field quantum key distribution (TF-QKD) protocols is investigated, focusing on phase noise from photon sources and connecting fibers. This work emphasizes the role of laser quality, network topology, fiber length, arm balance, and detector performance in determining key rates. Remarkably, it reveals that the leading TF-QKD protocols are similarly affected by phase noise despite different mechanisms. This study demonstrates duty cycle improvements of over a factor of two through narrow-linewidth lasers and phase-control techniques, highlighting the potential synergy with high-precision time and frequency distribution services. Ultrastable lasers, evolving toward integration and miniaturization, offer promising solutions for agile TF-QKD implementations on existing networks. Properly addressing phase noise and practical constraints allows for consistent key rate predictions, protocol selection, and layout design, crucial for establishing secure long-haul links for the quantum communication infrastructures under development in several countries.

In near-term quantum computers like noisy intermediate-scale quantum (NISQ) devices, reducing the impact of errors and decoherence is critical for practical implementation. Existing studies have primarily focused on Markovian noise sources; however, understanding the relationship between quantum error mitigation (QEM) and non-Markovian noise sources is essential, as these effects are practically unavoidable in most solid-state devices used for quantum computing. Here, a non-Markovian model of quantum state evolution and a QEM cost function of controlled-NOT (CNOT) gate operation are presented for NISQ devices interacting with an environment characterized by simple harmonic oscillators as a noise source. Using the projection operator formalism and both advanced and retarded propagators in time, the reduced-density operator is derived for output quantum states in a time-convolutionless form by solving the quantum Liouville equation. Output quantum state fluctuations are analyzed for identity and CNOT gate operations in two-qubit operations across various input states and compare these results with experimental data from ion-trap and superconducting quantum computing systems to estimate the key parameters of the QEM cost functions. These findings demonstrate that the QEM cost function increases as the coupling strength between the quantum system and its environment intensifies. This study highlights the significance of non-Markovian models for understanding quantum state evolution and the practical implications of the QEM cost function in assessing experimental results from NISQ devices.

Anomaly detection is crucial for identifying deviations from regular data. In article number 2300385, researchers from USTC (University of Science and Technology of China, Hefei) experimentally demonstrate the quantum anomaly detection with a spin processor embedded in a diamond, showing the quantum speedup in efficiently identifying anomalies. This cover illustrates that when a set of quantum samples, generated by a quantum machine (top-right), is transmitted to the diamond processor (bottom-right), the processor can learn its characteristics and identify whether a sample is an anomaly. [Cover design by Zhuoyue Xu (USTC).]

The problem of quantum measurement, which is considered as one of the most important open questions in physics, can be partially resolved by incorporating a process of spontaneous disentanglement. The cover image shows a limit cycle steady state of a Bloch vector in a two-spin system. Such a limit cycle steady state, which is prohibited in standard quantum mechanics, occurs due to disentanglement. For further details, see article number 2400036 by Eyal Buks.