Suppression of the radiative decay of atomic coherence in squeezed vacuum

TL;DR

This paper demonstrates that coupling an atom to quadrature squeezed vacuum can suppress its radiative decay below the natural linewidth, enhancing coherence times and enabling quantum state tomography, confirming fundamental quantum optics predictions.

Contribution

It provides the first experimental confirmation that squeezed vacuum can reduce atomic radiative decay below the natural limit, advancing quantum light-matter interaction studies.

Findings

Two-fold reduction of atomic radiative decay rate.

Transverse coherence time T_2 exceeds 2T_1.

Tomographic reconstruction of the squeezed state's Wigner distribution.

Abstract

Quantum fluctuations of the electromagnetic vacuum are responsible for physical effects such as the Casimir force and the radiative decay of atoms, and set fundamental limits on the sensitivity of measurements. Entanglement between photons can produce correlations that result in a reduction of these fluctuations below the vacuum level allowing measurements that surpass the standard quantum limit in sensitivity. Here we demonstrate that the radiative decay rate of an atom that is coupled to quadrature squeezed electromagnetic vacuum can be reduced below its natural linewidth. We observe a two-fold reduction of the transverse radiative decay rate of a superconducting artificial atom coupled to continuum squeezed vacuum generated by a Josephson parametric amplifier, allowing the transverse coherence time T_2 to exceed the vacuum decay limit of 2T_1. We demonstrate that the measured radiative decay dynamics can be used to tomographically reconstruct the Wigner distribution of the the itinerant squeezed state. Our results are the first confirmation of a canonical prediction of quantum optics and open the door to new studies of the quantum light-matter interaction.