Effects of Vacuum Fluctuation Suppression on Atomic Decay Rates

TL;DR

This paper investigates how atomic decay rates can be used to detect suppression of vacuum fluctuations in non-classical states, potentially allowing experimental measurement of negative energy densities and electric field fluctuations.

Contribution

It introduces a scheme to measure vacuum fluctuation suppression via atomic decay rates in non-classical cavity states, deriving bounds and estimating experimental feasibility.

Findings

Decay rates can indicate suppression of vacuum fluctuations.

Quantum inequality bounds limit decay rate reductions.

Experimental tests of negative energy density detection are potentially feasible.

Abstract

The use of atomic decay rates as a probe of sub-vacuum phenomena will be studied. Because electromagnetic vacuum fluctuations are essential for radiative decay of excited atomic states, decay rates can serve as a measure of the suppression of vacuum fluctuation in non-classical states, such as squeezed vacuum states. In such states the renormalized expectation value of the square of the electric field or the energy density can be periodically negative, representing suppression of vacuum fluctuations. We explore the extent to which atomic decays can be used to measure the mean squared electric field or energy density. We consider a scheme in which atoms in an excited state transit a closed cavity whose lowest mode contains photons in a non-classical state. The change in the decay probability of the atom in the cavity due to the non-classical state can, under certain circumstances, serve as a measure of the mean squared electric field or energy density in the cavity. We derive a quantum inequality bound on the decrease in this probability. We also show that the decrease in decay rate can sometimes be a measure of negative energy density or negative squared electric field. We make some estimates of the magnitude of this effect, which indicate that an experimental test might be possible.