The phase of an oscillator in quantum theory. What is it ’in reality’?
Lomonosov Moscow State University, Department of Physics, Leninskie Gory 1 build. 2, Moscow, 119991, Russian Federation
An analysis of the current theory of the quantum oscillator phase is presented. Predictions using existing approaches to the phase problem differ not only quantitatively
but also qualitatively. The question in the title has not yet been given a generally accepted answer. However, it is logical to argue that all the theoretically predicted properties of the phase are physically meaningful if appropriate measurements
are possible. Current phase measurement methods either involve the simultaneous (approximate) measurement of the amplitude and the phase or rely on the simultaneous measurement of quadrature amplitudes.