Conditional quantum evolution induced by continuous measurement for a mesoscopic qubit

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We consider the problem of an electron tunneling between two coupled quantum dots, a two-state quantum system (qubit), using a low-transparency point contact (PC) or tunnel junction as a detector continually measuring the position of the electron. We focus on the qubit dynamics conditioned on a particular realization of the actual measured current through the PC device. We illustrate the conditional evolutions by numerical simulations. The different behaviors between unconditional and conditional evolutions are demonstrated. The conditional qubit dynamics evolving from quantum jumps to quantum diffusion is presented.