A QUBIT-STATE READOUT ANALYSIS: QUANTUM TRAJECTORIES VS. MASTER EQUATION APPROACH

摘要

We demonstrate the connection between the quantum trajectory approach and the master equation approach of the "partially"-reduced density matrix by studying an initial charge qubit state readout experiment that uses a low-transparency point contact (PC) detector. We analyze an important ensemble quantity for the readout experiment, P(N,t), the probability distribution of finding N electrons that have tunneled through the PC barrier in time t. The simulation results for P(N,t) using 10000 quantum trajectories and the corresponding measurement records are, as expected, in very good agreement with those obtained from Fourier analysis of the "partially"-reduced density matrix. However, the quantum trajectory approach provides more information and more physical insight into the ensemble and time averaged quantity P(N,t).