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Bulletin of the American Physical Society

Superradiance in ultracold Rydberg atoms

Tun Wang, Robin Côté, Edward E. Eyler, S. M. Farooqi, P. L. Gould, Marijan Koštrun, D. Tong, D. Vrinceanu, Susanne F. Yelin

Published May 19, 2006• 0 citations
OpenAlex

Abstract

Experiments in dense, ultracold rubidium Rydberg atoms show a considerable decrease of excited state lifetimes compared to dilute gases. We find that this accelerated decay could be explained by collective and cooperative effects, leading to superradiance. We use a novel formalism to calculate effective decay times in a dense Rydberg gas for all decay channels. We find that the tendency to decay into the lowest levels is inverted in dense gases and that the now-dominant low-frequency decays favor a superradiant decay mode.

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Superradiance in ultracold Rydberg gases

T. Wang, Susanne F. Yelin, Robin Côté +6 more

Experiments in dense, ultracold gases of rubidium Rydberg atoms show a considerable decrease of the radiative excited state lifetimes compared to dilute gases. This accelerated decay is explained by collective and cooperative effects, leading to superradiance. A formalism to calculate effective decay times in a dense Rydberg gas shows that for these atoms the decay into nearby levels increases by up to three orders of magnitude. Excellent agreement between theory and experiment follows from this treatment of Rydberg decay behavior.

arXiv:quant-ph/0508135•Physical Review A•Mar 6, 2007•96 citations

Observation of blackbody radiation enhanced superradiance in ultracold Rydberg gases

Liping Hao, Zhengyang Bai, Jingxu Bai +6 more

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.

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Observation of electric field induced superradiance slowdown in ultracold Rydberg atomic gases

Yunhui He, Jingxu Bai, Yuechun Jiao +2 more

Atoms excited to electronically high-lying Rydberg states decay to low-energy states through spontaneous emission processes. We investigate the impact of a static electric field on the superradiant emission process between Rydberg |60 D 5/2 〉 and |61 P 3/2 〉 states in an ultracold Cesium Rydberg atom ensemble. We report experimental observations of a significant slowdown in superradiance upon applying an electric field. To understand the slowing down of superradiance, we employ a master equation in which Stark effects and collective decay are taken into account. We solve the master equation with the discrete truncated Wigner approximation (DTWA) method. Our numerical simulations demonstrate that superradiance decoherence is caused by the Stark shifts of the Rydberg level. Our theoretical simulations qualitatively match the experimental observations. Our work provides new insights into controlling quantum critical behaviors, with implications for quantum many-body dynamics, and the study of quantum phase transitions.

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Rydberg Molecules and Polarons in Ultracold Strontium Gases

Francisco Camargo

In this work I describe the excitation spectra of Rydberg atoms in ultracold gases of strontium and their decay mechanisms. In a few-body regime, we observe a highly structured spectrum re ecting excitation of ultralong-range molecules consisting of one or more ground-state atoms bound to the Rydberg core in potential wells formed by the Rydbergelectron wave function. In a many-body regime, with hundreds of ground-state atoms within the Rydberg orbital, the Rydberg atoms can be viewed as an impurity in a quantum gas, connecting to important concepts in condensed matter physics. The spectrum for impurity excitation displays signatures of polaronic states, in which the Rydberg atom signi cantly perturbs the density of the background gas. Additionally, decay channels of Rydberg excitations are examined by monitoring the time evolution of Rydberg populations. The measured lifetimes reveal new information on the decay processes of Rydberg molecules and place limits on the time scales over which studies involving Rydberg species in cold, dense atomic gases can be undertaken and limit the coherence times for such measurements.

•Aug 7, 2017•1 citation

Superradiance of ultracold cesium Rydberg |65D5/2〉 → |66P3/2〉

Liping Hao, Xiaoxuan 小萱 Han 韩, Suying Bai +3 more

We investigate Rydberg |65D5/2〉 → |66P3/2〉 superradiance in dense ultracold cesium atoms, where the ground atoms are excited to |65D5/2〉 Rydberg states via two-photon excitation in a standard magneto-optical trap. The superradiant spectrum of |65D5/2〉 → |66P3/2〉 is obtained using the state-selective field ionization technique. We observe its dynamic evolution process by varying the delay time of ionization field t d. The results show that the evolution process of |65D5/2〉 → |66P3/2〉 is much shorter than its radiation lifetime at room temperature, which verifies the superradiance effect. The dependence of the superradiance process on Rydberg atoms number N e and principal quantum number n is investigated. The results show that the superradiance becomes faster with increasing N e, while it is suppressed for stronger van der Waals (vdW) interactions. Superradiance has potential applications in quantum technologies, and the Rydberg atom is an ideal medium for superradiance. Our system is effective for studying the strong two-body interaction between Rydberg atoms.

Chinese Physics B•Jan 22, 2024•3 citations

Superradiance and Subradiance in Dense Atomic Gases: An Integrated Method

H. Ma, Oriol Rubies-Bigordà, Susanne F. Yelin

When atoms are coupled to a common electromagnetic environment, the exchange of photons through dipole-dipole interactions leads to the emergence of cooperative effects. As a particular example, superradiance arises from spontaneous emission when this exchange leads to constructive interference of the emitted photons. Here, we introduce an integrated method for studying cooperative radiation in many-body systems. This method, which allows to study extended systems with arbitrarily large number of particles, can be formulated by an effective, nonlinear, two-atom master equation that describes the dynamics using a closed form which treats single- and many-body terms on an equal footing. We apply this method to a homogeneous gas of initially inverted two-level atoms, and demonstrate the appearance of both superradiance and subradiance, identifying a many-body coherence term as the source of these cooperative effects. We describe the many-body induced broadening -- which is analytically found to scale with the optical depth of the system -- and light shifts, and distinguish spontaneous effects from induced ones. In addition, we theoretically predict the time-dependence of subradiance, and the phase change of the radiated field during the cooperative decay.

arXiv:2205.15255•May 30, 2022•4 citations
Experiments in dense, ultracold rubidium Rydberg atoms show a considerable decrease of excited state lifetimes compared to dilute gases. We find that this accelerated decay could be explained by collective and cooperative effects, leading to superradiance. We use a novel formalism to calculate effective decay times in a dense Rydberg gas for all decay channels. We find that the tendency to decay into the lowest levels is inverted in dense gases and that the now-dominant low-frequency decays favor a superradiant decay mode.
Experiments in dense, ultracold gases of rubidium Rydberg atoms show a considerable decrease of the radiative excited state lifetimes compared to dilute gases. This accelerated decay is explained by collective and cooperative effects, leading to superradiance. A formalism to calculate effective decay times in a dense Rydberg gas shows that for these atoms the decay into nearby levels increases by up to three orders of magnitude. Excellent agreement between theory and experiment follows from this treatment of Rydberg decay behavior.
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.
Atoms excited to electronically high-lying Rydberg states decay to low-energy states through spontaneous emission processes. We investigate the impact of a static electric field on the superradiant emission process between Rydberg |60 D 5/2 〉 and |61 P 3/2 〉 states in an ultracold Cesium Rydberg atom ensemble. We report experimental observations of a significant slowdown in superradiance upon applying an electric field. To understand the slowing down of superradiance, we employ a master equation in which Stark effects and collective decay are taken into account. We solve the master equation with the discrete truncated Wigner approximation (DTWA) method. Our numerical simulations demonstrate that superradiance decoherence is caused by the Stark shifts of the Rydberg level. Our theoretical simulations qualitatively match the experimental observations. Our work provides new insights into controlling quantum critical behaviors, with implications for quantum many-body dynamics, and the study of quantum phase transitions.
In this work I describe the excitation spectra of Rydberg atoms in ultracold gases of strontium and their decay mechanisms. In a few-body regime, we observe a highly structured spectrum re ecting excitation of ultralong-range molecules consisting of one or more ground-state atoms bound to the Rydberg core in potential wells formed by the Rydbergelectron wave function. In a many-body regime, with hundreds of ground-state atoms within the Rydberg orbital, the Rydberg atoms can be viewed as an impurity in a quantum gas, connecting to important concepts in condensed matter physics. The spectrum for impurity excitation displays signatures of polaronic states, in which the Rydberg atom signi cantly perturbs the density of the background gas. Additionally, decay channels of Rydberg excitations are examined by monitoring the time evolution of Rydberg populations. The measured lifetimes reveal new information on the decay processes of Rydberg molecules and place limits on the time scales over which studies involving Rydberg species in cold, dense atomic gases can be undertaken and limit the coherence times for such measurements.
We investigate Rydberg |65D5/2〉 → |66P3/2〉 superradiance in dense ultracold cesium atoms, where the ground atoms are excited to |65D5/2〉 Rydberg states via two-photon excitation in a standard magneto-optical trap. The superradiant spectrum of |65D5/2〉 → |66P3/2〉 is obtained using the state-selective field ionization technique. We observe its dynamic evolution process by varying the delay time of ionization field t d. The results show that the evolution process of |65D5/2〉 → |66P3/2〉 is much shorter than its radiation lifetime at room temperature, which verifies the superradiance effect. The dependence of the superradiance process on Rydberg atoms number N e and principal quantum number n is investigated. The results show that the superradiance becomes faster with increasing N e, while it is suppressed for stronger van der Waals (vdW) interactions. Superradiance has potential applications in quantum technologies, and the Rydberg atom is an ideal medium for superradiance. Our system is effective for studying the strong two-body interaction between Rydberg atoms.
When atoms are coupled to a common electromagnetic environment, the exchange of photons through dipole-dipole interactions leads to the emergence of cooperative effects. As a particular example, superradiance arises from spontaneous emission when this exchange leads to constructive interference of the emitted photons. Here, we introduce an integrated method for studying cooperative radiation in many-body systems. This method, which allows to study extended systems with arbitrarily large number of particles, can be formulated by an effective, nonlinear, two-atom master equation that describes the dynamics using a closed form which treats single- and many-body terms on an equal footing. We apply this method to a homogeneous gas of initially inverted two-level atoms, and demonstrate the appearance of both superradiance and subradiance, identifying a many-body coherence term as the source of these cooperative effects. We describe the many-body induced broadening -- which is analytically found to scale with the optical depth of the system -- and light shifts, and distinguish spontaneous effects from induced ones. In addition, we theoretically predict the time-dependence of subradiance, and the phase change of the radiated field during the cooperative decay.