On the Quantum Theory of Continuous Measurements
In the usual formulation of quantum mechanics only instantaneous measurements are considered. However, continuous (in time) measurements are often met in practice; for instance, the track of a particle can be approximately followed, or the density of matter in a fluid can be continuously observed, or some characteristic of a system can be monitored by some electronic device. Due to the work of many authors1–4 a very flexible formulation of quantum mechanics has been developed, by which continuous measurements too can be consistently introduced.2,5–8 A central point in this formulation is the notion of instrument,2 which contains both the probabilities for the measured quantity and the way the state of the system changes under measurement.
KeywordsContinuous Measurement Gravitational Wave Poisson Type Quantum Nondemolition Quantum Stochastic Calculus
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