Local and nonlocal observables in quantum optics

Abstract

It is pointed out that there exists an unambiguous definition of locality that enables one to distinguish local and nonlocal quantities. Observables of both types coexist in quantum optics but one must be very careful when attempting to measure them. A nonlocal observable which formally depends on the spatial position $\bi r$ cannot be {\em locally} measured without disturbing the measurements of this observable at all other positions.

Comment on the paper by K. Y. Bliokh et.al. New J. Phys. 16, 093037 (2014)

References in corpus (2)

• Conservation of the spin and orbital angular momenta in electromagnetism
• Why photons cannot be sharply localized

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• One more time on the helicity decomposition of spin and orbital optical currents
• Electric-magnetic duality as a quantum operator and more symmetries of $U(1)$ gauge theory