Operational time in quantum theory

Time, or spacetime in a broader sense, is a concept that lies at the heart of many fundamental aspects of physics. The operational view that time corresponds to what is measured by physical clocks together with the understanding that physical systems are, ultimately, quantum leads to the use of quantum clocks as frames of reference.

Investigating measurements of energy [Quantum 2022] and accelerating clocks [Commun. Phys. 2022] within clock frames of reference, we have shown that the effective dynamics in these contexts are generally governed by non-Hermitian Hamiltonians.

Currently, we have been trying to understand the physical consequences of these results. Moreover, as an alternative approach, we have been investigating whether modifications of the time parametrization can restore Hermiticity.

Novel consequences of the Aharonov-Bohm effect

The Aharonov-Bohm effect is a fundamental topological phenomenon with a wide range of applications. It consists of a charge encircling a region with a magnetic flux in a superposition of wavepackets having their relative phase affected by the flux. Even if the flux is completely isolated, like in the case of an infinite and impenetrable solenoid.

We have shown that special configurations of solenoids act as a type of mirror for charges with sufficiently low average energy [PRA 2020], possibly even creating topological bound states [PRA 2019]. Moreover, we have presented thought experiments in scenarios where the magnetic flux is quantized to detect the Aharonov-Bohm effect before the charge completes its loop [NJP 2023].

Ismael Lucas de Paiva’s webpage.
A site.