Subradiance and radiation trapping in cold atoms

Weiss, P.B.; Araújo, Michelle O.; Kaiser, Robin; Guerin, William

doi:10.1088/1367-2630/aac5d0

Cited by 55 publications

(51 citation statements)

References 56 publications

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“…The light-matter interaction can be strongly modified by collective coherent superradiance or subradiance, where the spontaneous emission speeds up or slows down [6][7][8][9]. Both superradiance and subradiance have been realized in various systems [10][11][12][13][14][15][16][17][18][19][20][21][22][23], and they provide novel opportunities to explore the interplay between collective excitations in materials and nonlinear effects in scattering of light [7,8]. Compared to superradiance, subradiance enables longer time for lightmatter interaction, and giant nonlinear response [24][25][26].…”

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confidence: 99%

Inelastic Scattering of Photon Pairs in Qubit Arrays with Subradiant States

Poshakinskiy

Lee

et al. 2019

Phys. Rev. Lett.

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We develop a rigorous theoretical approach for analyzing inelastic scattering of photon pairs in arrays of two-level qubits embedded in a waveguide. Our analysis reveals strong enhancement of the scattering when the energy of incoming photons resonates with the double-excited subradiant states. We identify the role of different double-excited states in the scattering such as superradiant, subradiant, and twilight states, being a product of single-excitation bright and subradiant states. Importantly, the N -excitation subradiant states can be engineered only if the number of qubits exceeds 2N . Both the subradiant and twilight states can generate long-lived photon-photon correlations, paving the way to a storage and processing of quantum information.

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confidence: 99%

Inelastic Scattering of Photon Pairs in Qubit Arrays with Subradiant States

Poshakinskiy

Lee

et al. 2019

Phys. Rev. Lett.

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“…After 60 ms of loading from the background vapor and a stage of compressed MOT (30 ms) we obtain a sample of N ≈ 3 × 10 9 atoms at a temperature T ≈ 100 µK with a Gaussian density distribution (peak densities ρ 0 ∼ 10 11 cm −3 and rms size R ≈ 1 mm). A more detailed description of the setup as well as the procedure to observe and analyze subradiance can be found in [4,22]. For this new series of experiments we now add an optical molasses in order to vary the temperature in a controlled manner.…”

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confidence: 99%

Robustness of Dicke subradiance against thermal decoherence

et al. 2019

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Subradiance is the cooperative inhibition of the radiation by several emitters coupled to the same electromagnetic modes. It has been predicted by Dicke in 1954 and only recently observed in cold atomic vapors. Here we address the question to what extend this cooperative effect survives outside the limit of frozen two-level systems by studying the subradiant decay in an ensemble of cold atoms as a function of the temperature. Experimentally, we observe only a slight decrease of the subradiant decay time when increasing the temperature up to several millikelvins, and in particular we measure subradiant decay rates that are much smaller than the Doppler broadening. This demonstrates that subradiance is surprisingly robust against thermal decoherence. The numerical simulations are in good agreement and allow us to extrapolate the behavior of subradiance at higher temperatures.Understanding the influence of decoherence or dephasing processes in cooperative effects such as super-and subradiance [1-7] is not only interesting from a fundamental point of view, but it is also important for the possible developments of photonic device exploiting cooperativity in the classical or quantum regime [8][9][10][11][12][13]. This is especially true if one wants to use solid-states devices [14,15], which are subject to phonon-induced decoherence. Previous theoretical studies of various toy models in the framework of open quantum systems have predicted some robustness of superradiance to noise and dephasing [16][17][18].In this Letter, we report an experimental study of thermal decoherence of subradiant Dicke states in large ensemble of cold atoms [4]. Indeed, even if laser-cooled atoms are not coupled to phonons, they are not completely frozen. Atomic motion has been shown to be a source of decoherence for coherent back-scattering [19] and to suppress the effect of recurrent scattering on the refractive index of dense atomic media [20,21]. Since subradiance is an interference effect involving very long time scales, it is expected to be particularly fragile.On the contrary, and quite surprisingly, we show here that subradiance in the linear-optics regime is robust against thermal motion. We observe only a slight decrease of the subradiant decay time when increasing the temperature up to several millikelvins, and in particular we measure subradiant decay rates Γ sub that are much smaller than the Doppler broadening Γ D , given by the width of the atomic velocity distribution. We also perform numerical simulations showing that the breakdown of subradiance only occurs when the Doppler broadening is on the same order of magnitude as the natural lifetime of the atomic transition Γ 0 . In practice, this means that subradiance can be observed and used at any "coldatom" temperature and even beyond.The experimental setup is based on a cloud of cold 87 Rb atoms prepared in a magneto-optical trap (MOT). After 60 ms of loading from the background vapor and a stage of compressed MOT (30 ms) we obtain a sample of N ≈ 3 × 10 9 atoms at a temperatu...

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“…The two previous models are very versatile as they can be used in various situations, including temporal dynamics [12] and fluctuations [36]. However, as far as steadystate scattering is concerned, it is sometimes useful to make use of the obvious result that the total scattered light equals the amount of light removed from the driving beam.…”

Section: Beer-lambert Lawmentioning

confidence: 99%

“…effect" ("Sh" in figures) computed by Beer-Lambert law [Eq. (12)]. We also make use of the possibilities to include a complicated level structure in the RW model: all results in this section were obtained for a F = 2 → F = 3 transition with a statistical equipopulated mixture of the Zeeman ground states, typical of 87 Rb experiments.…”

Section: B Random Walk and Beer-lambertmentioning

confidence: 99%

“…There has been a lot of research on this topic in the recent years, especially in the weak-intensity regime (linear-optics or single-photon regime); see, for example, the reviews [5,6]. Among the most important results, one can mention the difficulty of understanding the observed spectrum (shift and line shape) of light transmitted through dense clouds (see [7] and references therein) and the observation of super-and subradiance in the decay dynamics of light in dilute clouds [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

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Comparison of three approaches to light scattering by dilute cold atomic ensembles

Sokolov¹,

Guerin²

2019

J. Opt. Soc. Am. B

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Collective effects in atom-light interaction is of great importance for cold-atom-based quantum devices or fundamental studies on light transport in complex media. Here we discuss and compare three different approaches to light scattering by dilute cold atomic ensembles. The first approach is a coupled-dipole model, valid at low intensity, which includes cooperative effects, like superradiance, and other coherent properties. The second one is a random-walk model, which includes classical multiple scattering and neglects coherence effects. The third approach is a crude approximation only based on the attenuation of the excitation beam inside the medium, the so-called "shadow effect". We show that in the case of a low-density sample, the random walk approach is an excellent approximation for steady-state light scattering, and that the shadow effect surprisingly gives rather accurate results at least up to optical depths on the order of 15.

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Subradiance and radiation trapping in cold atoms

Cited by 55 publications

References 56 publications

Inelastic Scattering of Photon Pairs in Qubit Arrays with Subradiant States

Inelastic Scattering of Photon Pairs in Qubit Arrays with Subradiant States

Robustness of Dicke subradiance against thermal decoherence

Comparison of three approaches to light scattering by dilute cold atomic ensembles

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