Observation of Blackbody Radiation Enhanced Superradiance in ultracold Rydberg Gases

TL;DR

This study demonstrates that blackbody radiation at room temperature enhances superradiance in ultracold Rydberg gases, revealing new many-body dynamics and potential applications in microwave thermometry.

Contribution

It provides the first direct observation of BBR-enhanced superradiance in ultracold Rydberg atoms and explores how interactions and electric fields influence this collective emission.

Findings

BBR significantly increases Rydberg state decay rates.

Superradiance dynamics are altered by van der Waals interactions.

Static electric fields slow down superradiant decay.

Abstract

An ensemble of excited atoms can synchronize emission of light collectively in a process known as superradiance when its characteristic size is smaller than the wavelength of emitted photons. The underlying superradiance depends strongly on electromagnetic (photon) fields surrounding the atomic ensemble. High mode densities of microwave photons from $300\,$K blackbody radiation (BBR) significantly enhance decay rates of Rydberg states to neighbouring states, enabling superradiance that is not possible with bare vacuum induced spontaneous decay. Here we report observations of the superradiance of ultracold Rydberg atoms embedded in a bath of room-temperature photons. The temporal evolution of the Rydberg $|nD\rangle$ to $|(n+1)P\rangle$ superradiant decay of Cs atoms ($n$ the principal quantum number) is measured directly in free space. Theoretical simulations confirm the BBR enhanced superradiance in large Rydberg ensembles. We demonstrate that the van der Waals interactions between Rydberg atoms change the superradiant dynamics and modify the scaling of the superradiance. In the presence of static electric fields, we find that the superradiance becomes slow, potentially due to many-body interaction induced dephasing. Our study provides insights into many-body dynamics of interacting atoms coupled to thermal BBR, and might open a route to the design of blackbody thermometry at microwave frequencies via collective, dissipative photon-atom interactions.