Continuous quantum measurement for general Gaussian unravelings can exist
: Megier N, Strunz WT, Luoma K
Publisher: AMER PHYSICAL SOC
: 2020
: Physical Review Research
: PHYSICAL REVIEW RESEARCH
: PHYS REV RES
: ARTN 043376
: 2
: 8
DOI: https://doi.org/10.1103/PhysRevResearch.2.043376
Quantum measurements and the associated state changes are properly described in the language of instruments. We investigate the properties of a time continuous family of instruments associated with the recently introduced class of general Gaussian non-Markovian stochastic Schrodinger equations. In this article we find that when the covariance matrix for the Gaussian noise satisfies a particular delta-function constraint, the measurement interpretation is possible for a class of models with self-adjoint coupling operator. This class contains, for example the spin-boson and quantum Brownian motion models with colored bath correlation functions. Remarkably, due to quantum memory effects the reduced state, in general, does not obey a closed form master equation while the unraveling has a time continuous measurement interpretation.