Optical properties of semiconductors coupled to a superconductor and their application to quantum information and communication

Abstract

Superconducting (SC) effects on optical processes in semiconductors are presented. At a superconductor (S)- semiconductor (N) interface, Cooper pairs penetrate from S to N, which is explained with the concept of Andreev reflection. We have studied SC light emitting diodes with quantum well emitting layers and observed an increase in luminescence intensity and an enhancement of the photon emission rate below the SC critical temperature (T_C). We prepared a new uniformly n-type doped quantum dot (QD) sample that is in contact with SC niobium (Nb). Below T_C, we observed a clear spectral change that reflects the SC density of states. We attribute this new finding to the QD discrete energy levels, and discuss the possibility of generating entangled photon pairs deterministically from a single QD with the SC effect.