Measuring time with stationary quantum clocks

          @misc{ pirsa_PIRSA:21060103,
            doi = {10.48660/21060103},
            url = {https://pirsa.org/21060103},
            author = {Woods, Mischa},
            keywords = {Quantum Foundations},
            language = {en},
            title = {Measuring time with stationary quantum clocks},
            publisher = {Perimeter Institute},
            year = {2021},
            month = {jun},
            note = {PIRSA:21060103 see, \url{https://pirsa.org}}
          }
          

Abstract

Time plays a fundamental role in our ability to make sense of the physical laws in the world around us. The nature of time has puzzled people –- from the ancient Greeks to the present day -– resulting in a long running debate between philosophers and physicists alike to whether time needs change to exist (the so-called relatival theory), or whether time flows regardless of change (the so-called substantival theory). One way to decide between the two is to attempt to measure the flow of time with a stationary clock, since if time were substantival, the flow of time would manifest itself in the experiment. Alas, conventional wisdom suggests that in order for a clock to function, it cannot be a static object, thus rendering this experiment seemingly impossible. We show that counter-intuitively, a quantum clock can measure the passage of time, even while being switched off, lending support for the substantival theory of time.