Steady-state superradiance in free-space atomic ensembles

We investigate the evolution of the second-order temporal coherence during the emission of a superradiant pulse by an elongated cloud of cold Rb atoms in free space. To do so, we measure the two-times intensity correlation function g_{N}^{(2)}(t_{1},t_{2}) following the pulsed excitation of the cloud. By monitoring g_{N}^{(2)}(t,t) during the pulse, we observe the establishment of second-order coherence, and contrast it with the situation where the cloud is initially prepared in a steady state. We compare our findings to the predictions of the Dicke model, using an effective atom number to account for finite size effects, finding that the model reproduces the observed trend at early time. For longer times, we observe a subradiant decay, a feature that goes beyond Dicke's model. Finally, we measure the g_{N}^{(2)}(t_{1},t_{2}) at different times and observe the appearance of anticorrelations during the pulse that are not present when starting from a steady state.We investigate the evolution of the second-order temporal coherence during the emission of a superradiant pulse by an elongated cloud of cold Rb atoms in free space. To do so, we measure the two-times intensity correlation function g_{N}^{(2)}(t_{1},t_{2}) following the pulsed excitation of the cloud. By monitoring g_{N}^{(2)}(t,t) during the pulse, we observe the establishment of second-order coherence, and contrast it with the situation where the cloud is initially prepared in a steady state. We compare our findings to the predictions of the Dicke model, using an effective atom number to account for finite size effects, finding that the model reproduces the observed trend at early time. For longer times, we observe a subradiant decay, a feature that goes beyond Dicke's model. Finally, we measure the g_{N}^{(2)}(t_{1},t_{2}) at different times and observe the appearance of anticorrelations during the pulse that are not present when starting from a steady state.

arXiv:2410.08652Physical Review LettersApr 15, 202519 citations

Breakdown of steady-state superradiance in extended driven atomic arrays

Stefan Ostermann, Oriol Rubies-Bigordà, Victoria Zhang +1 more

Recent advances in generating well controlled dense arrangements of individual atoms in free space have generated interest in understanding how the extended nature of these systems influences superradiance phenomena. Here, we provide an in-depth analysis on how space-dependent light shifts and decay rates induced by dipole-dipole interactions modify the steady-state properties of coherently driven arrays of quantum emitters. We characterize the steady-state phase diagram, with particular focus on the radiative properties in the steady state. Interestingly, we find that diverging from the well-established Dicke paradigm of equal all-to-all interactions significantly modifies the emission properties. In particular, the prominent quadratic scaling of the radiated light intensity with particle number in the steady state—a hallmark of steady-state Dicke superradiance—is entirely suppressed, resulting in only linear scaling with particle number. We show that this breakdown of steady-state superradiance occurs due to the emergence of additional dissipation channels that populate not only superradiant states but also subradiant ones. The additional contribution of subradiant dark states in the dynamics leads to a divergence in the time scales needed to achieve steady states. Building on this, we further show that measurements taken at finite times for extended atom ensembles reveal properties closely mirroring the idealized Dicke scenario. Published by the American Physical Society 2024Recent advances in generating well controlled dense arrangements of individual atoms in free space have generated interest in understanding how the extended nature of these systems influences superradiance phenomena. Here, we provide an in-depth analysis on how space-dependent light shifts and decay rates induced by dipole-dipole interactions modify the steady-state properties of coherently driven arrays of quantum emitters. We characterize the steady-state phase diagram, with particular focus on the radiative properties in the steady state. Interestingly, we find that diverging from the well-established Dicke paradigm of equal all-to-all interactions significantly modifies the emission properties. In particular, the prominent quadratic scaling of the radiated light intensity with particle number in the steady state—a hallmark of steady-state Dicke superradiance—is entirely suppressed, resulting in only linear scaling with particle number. We show that this breakdown of steady-state superradiance occurs due to the emergence of additional dissipation channels that populate not only superradiant states but also subradiant ones. The additional contribution of subradiant dark states in the dynamics leads to a divergence in the time scales needed to achieve steady states. Building on this, we further show that measurements taken at finite times for extended atom ensembles reveal properties closely mirroring the idealized Dicke scenario. Published by the American Physical Society 2024

arXiv:2311.10824Physical Review ResearchMay 23, 202417 citations

Atomic coherent-state representation of superradiance

Lorenzo M. Narducci, C. M. Bowden, C. Alton Coulter

Lettere al nuovo cimento della societa italiana di fisica/Lettere al nuovo cimentoSep 1, 19738 citations

Fock-state superradiance in a cold atomic ensemble

D. F. Barros, Luis F. Muñoz-Martínez, Luis Ortiz-Gutiérrez +7 more

arXiv:1809.07787Optics CommunicationsJan 19, 20191 citation

Observation of a non-equilibrium superradiant phase transition in free space

Giovanni Ferioli, Antoine Glicenstein, Igor Ferrier-Barbut +1 more

We observe a non-equilibrium phase transition in a driven dissipative quantum system consisting of an pencil-shape cloud of up to $N\approx 2000$ laser-cooled atoms in free space, optically excited along its main axis. We find that our data are well reproduced by the Driven Dicke model, which assumes a sub-wavelength sample volume, by simply using an effective atom number. By measuring the excited state population of the atoms and the light emitted in the superradiant mode, we characterize the dynamics of the system and its steady-state properties. In particular, we observe the characteristic $N^2$ scaling of the photon emission rate in the superradiant phase, thus demonstrating steady-state superradiance in free space. Finally, we observe a modification of the statistics of the superradiant light as we cross the phase transition.We observe a non-equilibrium phase transition in a driven dissipative quantum system consisting of an pencil-shape cloud of up to $N\approx 2000$ laser-cooled atoms in free space, optically excited along its main axis. We find that our data are well reproduced by the Driven Dicke model, which assumes a sub-wavelength sample volume, by simply using an effective atom number. By measuring the excited state population of the atoms and the light emitted in the superradiant mode, we characterize the dynamics of the system and its steady-state properties. In particular, we observe the characteristic $N^2$ scaling of the photon emission rate in the superradiant phase, thus demonstrating steady-state superradiance in free space. Finally, we observe a modification of the statistics of the superradiant light as we cross the phase transition.

Jul 1, 20222 citations

We observe a non-equilibrium phase transition in a driven dissipative quantum system consisting of an pencil-shape cloud of up to

N\approx 2000

laser-cooled atoms in free space, optically excited along its main axis. We find that our data are well reproduced by the Driven Dicke model, which assumes a sub-wavelength sample volume, by simply using an effective atom number. By measuring the excited state population of the atoms and the light emitted in the superradiant mode, we characterize the dynamics of the system and its steady-state properties. In particular, we observe the characteristic

N^2

scaling of the photon emission rate in the superradiant phase, thus demonstrating steady-state superradiance in free space. Finally, we observe a modification of the statistics of the superradiant light as we cross the phase transition.