Decoherence due to elastic Rayleigh scattering

TL;DR

This paper investigates how elastic Rayleigh scattering causes decoherence in hyperfine ground-state superpositions, revealing it can be the dominant decoherence mechanism under certain conditions, with both theoretical and experimental validation.

Contribution

It demonstrates that elastic Rayleigh scattering can dominate decoherence and introduces a new understanding of how scattering amplitudes interfere, supported by calculations and experiments.

Findings

Elastic Rayleigh scattering can be the main source of decoherence.

Decoherence rate depends on the difference of scattering amplitudes squared.

Constructive interference of amplitudes affects decoherence even with equal scattering rates.

Abstract

We present theoretical and experimental studies of the decoherence of hyperfine ground-state superpositions due to elastic Rayleigh scattering of light off-resonant with higher lying excited states. We demonstrate that under appropriate conditions, elastic Rayleigh scattering can be the dominant source of decoherence, contrary to previous discussions in the literature. We show that the elastic-scattering decoherence rate of a two-level system is given by the square of the difference between the elastic-scattering \textit{amplitudes} for the two levels, and that for certain detunings of the light, the amplitudes can interfere constructively even when the elastic scattering \textit{rates} from the two levels are equal. We confirm this prediction through calculations and measurements of the total decoherence rate for a superposition of the valence electron spin levels in the ground state of $^9$Be$^+$ in a 4.5 T magnetic field.