Mainz 2017 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
Q: Fachverband Quantenoptik und Photonik
Q 31: Poster: Quantum Optics and Photonics I
Q 31.63: Poster
Tuesday, March 7, 2017, 17:00–19:00, P OG1+2
Backwards Master Equation — •Jonas Lammers1,2 and Klemens Hammerer1,2 — 1Institut für Theoretische Physik, Leibniz Universität Hannover — 2Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Leibniz Universität Hannover
The evolution of a quantum system undergoing continuous measurements is governed by the so-called conditional stochastic master equation. Using the past measurement record, it predicts the state of the system at a given time. We develop a method which allows to verify that state by retrodiction, using the future measurement record to compute the backwards evolution of the system.
We derive the stochastic backwards evolution equation of a quantum optical system using only basic quantum mechanics. The conditions on the system are very general so as to make the formalism applicable to a wide range of different setups. As an application, we examine how a Gaussian state evolves in a linear system, and compute the backwards equations of motion of its first and second moments. More concretely, we consider a one-dimensional harmonic oscillator under continuous position measurements coupled to a thermal bath. The proposed procedure allows to affirm the presence of desired properties such as entanglement or other non-classical features in a past quantum state, or even its whole density matrix.