High-speed visible light communication based on micro-LED:A technology with wide applications in next generation communication

The evolution of next-generation cellular networks is aimed at creating faster,more reliable solutions.Both the next-generation 6G network and the metaverse require high transmission speeds.Visible light communication(VLC)is deemed an important ancillary technology to wireless communication.It has shown potential for a wide range of applications in next-generation communication.Micro light-emitting diodes(μLEDs)are ideal light sources for high-speed VLC,owing to their high modulation bandwidths.In this review,an overview ofμLEDs for VLC is presented.Methods to improve the modulation bandwidth are discussed in terms of epitaxy optimization,crystal orientation,and active region structure.Moreover,electroluminescent white LEDs,photoluminescent white LEDs based on phosphor or quantum-dot color conversion,andμLED-based detectors for VLC are introduced.Finally,the latest high-speed VLC applications and the application prospects of VLC in 6G are introduced,including underwater VLC and artificial intelligence-based VLC systems.

Typicality at quantum-critical points

We discuss the concept of typicality of quantum states at quantum-critical points, using projector Monte Carlo simu- lations of an S ---- 1/2 bilayer Heisenberg antiferromagnet as an illustration. With the projection （imaginary） time t scaled as t= aLz, L being the system length and z the dynamic critical exponent （which takes the value z = 1 in the bilayer model studied here）, a critical point can be identified which asymptotically flows to the correct location and universality class with increasing L, independently of the prefactor a and the initial state. Varying the proportionality factor a and the initial state only changes the cross-over behavior into the asymptotic large-L behavior. In some cases, choosing an optimal factor a may also lead to the vanishing of the leading finite-size corrections. The observation of typicality can be used to speed up simulations of quantum criticality, not only within the Monte Carlo approach but also with other numerical methods where imaginary-time evolution is employed, e.g., tensor network states, as it is not necessary to evolve fully to the ground state but only for sufficiently long times to reach the typicality regime.