Observation of Dicke Superradiance for Two Artificial Atoms in a Cavity with High Decay Rate

TL;DR

This paper demonstrates Dicke superradiance with two superconducting qubits in a microwave cavity, showing altered emission dynamics due to emitter interaction, confirmed through time-resolved measurements and density matrix reconstruction.

Contribution

It provides an experimental realization of Dicke's two-emitter superradiance using superconducting qubits, highlighting the effects of emitter interaction in a high decay rate cavity.

Findings

Observation of superradiant emission in two superconducting qubits

Time-resolved measurement of emitted power shows superradiance dynamics

Reconstruction of the emitted field's density matrix confirms superradiance

Abstract

An individual excited two level system decays to its ground state by emitting a single photon in a process known as spontaneous emission. In accordance with quantum theory the probability of detecting the emitted photon decreases exponentially with the time passed since the excitation of the two level system. In 1954 Dicke first considered the more subtle situation in which two emitters decay in close proximity to each other. He argued that the emission dynamics of a single two level system is altered by the presence of a second one, even if it is in its ground state. Here, we present a close to ideal realization of Dicke's original two-spin Gedankenexperiment, using a system of two individually controllable superconducting qubits weakly coupled to a microwave cavity with a fast decay rate. The two-emitter case of superradiance is explicitly demonstrated both in time-resolved measurements of the emitted power and by fully reconstructing the density matrix of the emitted field in the photon number basis.