Partial-measurement–induced entanglement dynamics in a Josephson-junction system

We study the continuous-partial-measurement–induced entanglement dynamics of two phase qubits in a superconducting loop coupled by capacity. It is shown that entanglement does not change monotonously during the measurement process, and is robust against small fluctuations of the tunneling probability. We find entanglement sudden birth induced by continuous partial measurement for an initially separable state. Furthermore, we show that with the help of continuous partial measurement an almost pure state can be generated from a totally mixed state. ©2010