Recoil-induced subradiance in a cold atomic gas

TL;DR

This paper demonstrates how subradiance, a cooperative suppression of spontaneous emission, can be achieved in a cold atomic gas within a ring cavity using a two-frequency laser, leading to quantum correlations among atomic momentum states.

Contribution

It introduces a method to realize and analyze quantum subradiant states in cold atoms with a three-level momentum cascade, including a semiclassical and quantum description.

Findings

Formation of a stationary subradiant state after photon emission

Demonstration of anti-bunching and quantum correlations among atomic modes

Calculation of the quantum subradiant state's Wigner function

Abstract

Subradiance, i.e. the cooperative inhibition of spontaneous emission by destructive interatomic interference, can be realized in a cold atomic sample confined in a ring cavity and lightened by a two-frequency laser. The atoms, scattering the photons of the two laser fields into the cavity-mode, recoil and change their momentum. Under proper conditions the atomic initial momentum state and the first two momentum recoil states form a three-level degenerate cascade. A stationary subradiant state is obtained after that the scattered photons have left the cavity, leaving the atoms in a coherent superposition of the three collective momentum states. After a semiclassical description of the process, we calculate the quantum subradiant state and its Wigner function. Anti-bunching and quantum correlations between the three atomic modes of the subradiant state are demonstrated.