Howard Wiseman

What is quantum about quantum trajectories?
(Wednesday, 27 August, 2:15-3:00)

Abstract:

Quantum trajectory equations are stochastic equations for the state of an open quantum system conditioned on a monitoring i.e. a continous-in-time measurement of a bath to which it is coupled. They are closely related to classical stochastic equations for classical probability distributions called filtering equations (e.g. the Kalman filter) and indeed are also called quantum filtering equations. Given this close relation, the question arises: what is quantum about quantum trajectories? In this talk I suggest that the answer lies in the ability of an experimenter to choose different monitoring schemes. Moreover, I propose that there is an experimental way to distinguish between cases where this choice does demonstrate the quantum nature of the noise to be demonstrated, and those where it does not, making use of the concepts in the recent work: H. M. Wiseman, S. J. Jones, and A. C. Doherty, “Steering, Entanglement, Nonlocality, and the EPR Paradox”, Phys. Rev. Lett. 98, 140402 (2007).