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.

PACS: 03.65.−w, 42.50.−p, 42.50.Dv (all) DOI: 10.1070/PU2002v045n08ABEH001219 URL: https://ufn.ru/en/articles/2002/8/c/ 000179657600003 Citation: Vorontsov Yu I "The phase of an oscillator in quantum theory. What is it 'in reality'?" Phys. Usp. 45 847–868 (2002) BibTexBibNote ® (generic)BibNote ® (RIS)MedlineRefWorks Оригинал: Воронцов Ю И «Фаза осциллятора в квантовой теории. Что это такое „на самом деле“?» УФН 172 907–929 (2002); DOI: 10.3367/UFNr.0172.200208c.0907