QUANTUM DYNAMICS OF SUPERCONDUCTING QUBIT READOUT WITH A DRIVEN NONLINEAR JOSEPHSON OSCILLATOR

摘要

The Josephson bifurcation amplifier (JBA) readout process of a superconducting qubit is analyzed quantum mechanically. We examined the dynamics of the density operator of a. probe (a driven nonlinear oscillator) and a qubit coupled system during the measurement process. We have observed the qubit-probe (JBA) entangled state and it is divided into two separable states at the moment of the JBA transition begins. To readout the measurement result, however, we must wait until the two JBA states are macroscopically well separated.