Quasi-probability distributions for observables in dynamic systems

Understand

We develop a general framework to investigate fluctuations of non-commuting observables.

• To this end, we consider the Keldysh quasi-probability distribution (KQPD).
• This distribution provides a measurement-independent description of the observables of interest and their time-evolution.
• Nevertheless, positive probability distributions for measurement outcomes can be obtained from the KQPD by taking into account the effect of measurement back-action and imprecision.