Correlation function and mutual information are two powerful tools to characterize the correlations in a quantum state of a composite system, widely used in many-body physics and in quantum information science, respectively. We find that these two tools may give different conclusions about the order of the degrees of correlation in two specific two-qubit states. This result implies that the orderings of bipartite quantum states according to the degrees of correlation depend on which correlation measure we adopt.

The development of electric vehicles has received worldwide attention in the background of reducing carbon emissions, wherein lithium‐ion batteries (LIBs) become the primary energy supply systems. However, commercial graphite‐based anodes in LIBs currently confront significant difficulty in enduring ultrahigh power input due to the slow Li+ transport rate and the low intercalation potential. This will, in turn, cause dramatic capacity decay and lithium plating. The 2D layered materials (2DLMs) recently emerge as new fast‐charging anodes and hold huge promise for resolving the problems owing to the synergistic effect of a lower Li+ diffusion barrier, a proper Li+ intercalation potential, and a higher theoretical specific capacity with using them. In this review, the background and fundamentals of fast‐charging for LIBs are first introduced. Then the research progress recently made for 2DLMs used for fast‐charging anodes are elaborated and discussed. Some emerging research directions in this field with a short outlook on future studies are further discussed.

Blue-violet wavelength multiplexing offers the capability to enhance the operational capacity and efficiency in optical information processing, underwater communications, biology, and medicine. Here we present a specially designed atomic scheme of cesium for simultaneously generating two blue-violet lasers at 456 and 459 nm via four-wave-mixing (FWM)-based upconversion processes. We experimentally and theoretically show that a double-diamond-type coherent system pumped with 852 and 921 nm lasers is responsible for the efficient generation of the two blue-violet lasers. In this system, the large population inversions lead to self-amplified spontaneous emissions at 15.6 and 12.1 µ m , which, in turn, serve as the seeds for enhanced double FWM processes with dual-wavelength upconversions.