Southwest Quantum Information and Technology

Open quantum systems with arbitrary initial conditions

Presenting Author: Gerardo Paz-Silva, Griffith University (Australia)
Contributing Author(s): Michael Hall and Howard Wiseman

The theory of Open Quantum Systems is concerned with the prediction and control of the dynamics of a quantum system in the presence of interactions with external degrees of freedom. This is a highly non-trivial problem, and in its study two assumptions are usually made: (A1) the state of system and bath is factorizable at time t=0, and (A2) certain knowledge of the bath, e.g., of the bath correlations, is assumed despite (by definition) not being fully accessible. Seeking to replace the assumption character of (A2) by measurable information, recent years have seen the emergence of the so-called Quantum Noise Spectroscopy protocols. These, provided (A1) holds, use the measurable response of a quantum system to its bath and different control scenarios, in order to extract information regarding the bath correlations (with respect to the reduced density matrix of the bath). In this talk, by introducing a new universal density matrix decomposition we show how (A1) can be naturally removed from current calculations methods, such as master equations, and, additionally, how the notion of Quantum Noise Spectroscopy can be extended to the case where system and bath are initially correlated. Thus, we show how (A1) and (A2) can in principle be simultaneously discarded from the set of assumptions made in the theory of Open Quantum Systems. We further discuss consequences and applications of our decomposition method to quantum steering and to the understanding of quantum channels.

(Session 5 : Thursday from 5:00pm - 7:00pm)