Observation of blackbody radiation enhanced superradiance in ultracold Rydberg gases

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⟩ to |(n + 1)P⟩ 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.

Lifetime Measurement of Cesium Atoms Using a Cold Rydberg Gas

“…It is noted that the superradiation effect has a negligible effect on the lifetime measurement in this work. When the Rydberg density is larger than ∼10 10 cm −3 , the superradiation will strongly accelerate the decay rate and modify the lifetime of Rydberg state [4,25]. The high precision measurement of the lifetime provides a powerful tool for investigating the cross section for the quenching collision and also has a significant correction to quantum defects.…”

“…In this section, we consider the effect of the BBR on the decay rate of Rydberg state. As we know that the room temperature BBR has a negligible effect for the ground atom, but has a strong effect for electronically high-lying Rydberg states and enhance the decay rate of Rydberg states [22][23][24][25]. Taking into account the BBR effect, the effective radiation decay rate of Rydberg atoms Γ e f f (T) can be written as…”

Superradiance-induced multistability in one-dimensional driven Rydberg lattice gases

“…the Dicke limit R jk λ [2], decay becomes collective such that its rate depends on the number of atoms in the ensemble, and hence can be much larger than the individual decay rate [3]. Since predicted by Dicke, superradiance has been confirmed in a variety experimental settings including Rydberg atoms [4][5][6][7][8], cavities [9][10][11], Bose-Einstein condensates [12][13][14], and quantum dots [15]. On the other hand, insights gained from the study of superradiance allow us to develop applications in quantum metrology [16,17], narrow linewidth lasers [18][19][20] and atomic clocks [21], etc.…”

Many-Body Radiative Decay in Strongly Interacting Rydberg Ensembles

“…Radiative decay is therefore here not expected to acquire a collective character and is typically modelled as a singleatom process. Note, that super-and subradiance can nevertheless occur -and have been investigated -in Rydberg gases [35][36][37][38]. However, in these studies the considered radiative transitions take place among Rydberg states and the associated wavelengths are on the order of millimetres to centimetres [39].…”