Enhanced cross-Kerr effect for probing tunnelling in coupled quantum dots

An efficient scheme for probing electron tunnelling is proposed based on the enhanced cross-Kerr nonlinearity in a double-dot system. Due to resonant tunnelling, the cross-Kerr nonlinearity arises in a transparency window. Its intensity is nearly two orders of magnitude greater than that of the self-Kerr effect under any given conditions, where residual absorption is suppressed due to the competition of nonlinear gain and absorption. The enhanced cross-Kerr effect is sensitive to the tunnelling, so the probe spectrum can detect subtle tunnelling changes. The simulation results show that the probe sensitivity of the nonlinear phase shift is about 0.28 rad/mu eV.