AJAisling Johnson

Aisling Johnson

Laboratoire Charles Fabry
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Aisling Johnson has a total of 36 co-authors. Here are the top co-authors by number of shared publications:

Latest Publications

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    Ultrastrong linear optomechanical interaction

    by Kahan Dare, Jannek J. Hansen, Iurie Coroli, Aisling Johnson, Markus Aspelmeyer, Uroš Delić

    Light-matter interaction in the ultrastrong coupling regime can be used to generate exotic ground states with two-mode squeezing and may be useful for quantum-enhanced sensing. Current demonstrations of ultrastrong coupling have been performed in fundamentally nonlinear systems. We report a cavity optomechanical system that operates in the linear coupling regime, reaching a maximum coupling of g x / Ω x = 0.55 ± 0.02 . Such a system is inherently unstable, which may in the future enable strong mechanical squeezing. Published by the American Physical Society 2024

    Cited by 12
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    Dry launching of silica nanoparticles in vacuum

    by Ayub Khodaee, Kahan Dare, Aisling Johnson, Uroš Delić, Markus Aspelmeyer

    Clean loading of silica nanoparticles with a radius as small as ∼50 nm is required for experiments in levitated optomechanics that operate in ultra-high vacuum. We present a cheap and simple experimental method for dry launching of silica nanoparticles by shaking from a polytetrafluoroethylene surface (PTFE). We report on the successful launching of single silica nanoparticles with a minimum radius of 43 nm, which is enabled by the low stiction to the launching surface. Nanoparticles with radii of 43 and 71.5 nm are launched with a high flux and small spread. The measured velocities are significantly smaller than 1 m/s. The demonstrated launching method allows for controlled loading of dry nanoparticles with radii as small as 43 nm into optical traps in (ultra-)high vacuum, although we anticipate that loading of smaller sizes is equally feasible.

    Cited by 20
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    Squeezed Light from a Levitated Nanoparticle at Room Temperature

    by Lorenzo Magrini, Victor A. Camarena-Chávez, Constanze Bach, Aisling Johnson, Markus Aspelmeyer

    Quantum measurements of mechanical systems can generate optical squeezing via ponderomotive forces. Its observation requires high environmental isolation and efficient detection, typically achieved by using cryogenic cooling and optical cavities. Here, we realize these conditions by measuring the position of an optically levitated nanoparticle at room temperature and without the overhead of an optical cavity. We use a fast heterodyne detection to reconstruct simultaneously orthogonal optical quadratures, and observe a noise reduction of 9%±0.5% below shot noise. Our experiment offers a novel, cavityless platform for squeezed-light enhanced sensing. At the same time it delineates a clear and simple strategy toward observation of stationary optomechanical entanglement.

    Cited by 61
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    Collective Radiative Dynamics of an Ensemble of Cold Atoms Coupled to an Optical Waveguide

    by Riccardo Pennetta, Martin Blaha, Aisling Johnson, Daniel Lechner, Philipp Schneeweiss, Jürgen Volz, Arno Rauschenbeutel

    We experimentally and theoretically investigate collective radiative effects in an ensemble of cold atoms coupled to a single-mode optical nanofiber. Our analysis unveils the microscopic dynamics of the system, showing that collective interactions between the atoms and a single guided photon gradually build up along the atomic array in the direction of propagation of light. These results are supported by time-resolved measurements of the light transmitted and reflected by the ensemble after excitation via nanofiber-guided laser pulses, whose rise and fall times are shorter than the atomic lifetime. Superradiant decays more than 1 order of magnitude faster than the single-atom free-space decay rate are observed for emission in the forward-propagating guided mode, while at the same time, no speed-up of the decay rate is measured in the backward direction. In addition, position-resolved measurements of the light that is transmitted past the atoms are performed by inserting the nanofiber-coupled atomic array in a 45-m-long fiber ring resonator, which allow us to experimentally reveal the progressive growth of the collective response of the atomic ensemble. Our results highlight the unique opportunities offered by nanophotonic cold atom systems for the experimental investigation of collective light-matter interaction.

    Cited by 118
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    Beyond the Tavis-Cummings model: Revisiting cavity QED with ensembles of quantum emitters

    by Martin Blaha, Aisling Johnson, Arno Rauschenbeutel, Jürgen Volz

    The interaction of an ensemble of N two-level quantum emitters with a single-mode electromagnetic field is described by the Tavis-Cummings model. There, the collectively enhanced light-matter coupling strength is given by gN=Ng¯1, where g¯1 is the ensemble-averaged single-emitter coupling strength. This model has been employed to describe and to analyze numerous cavity-based experiments. Here, we show that this is only justified if the effective scattering rate into noncavity modes is negligible compared to the cavity's free-spectral range. In terms of experimental parameters, this requires that the optical depth of the ensemble is low, a condition that is violated in several state-of-the-art experiments. We give quantitative conditions for the validity of the Tavis-Cummings model and derive a more general Hamiltonian description that takes into account the cascaded interaction of the photons with all consecutive emitters. We show that the predictions of our cascaded model can differ quantitatively and even qualitatively from those obtained with the Tavis-Cummings model. Finally, we present experimental data, for which the deviation from the predictions of the Tavis-Cummings model is apparent. Our findings are relevant for all experiments in which optically dense ensembles of quantum emitters are coupled to an optical resonator.

    Cited by 56
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    Observation of Collective Superstrong Coupling of Cold Atoms to a 30-m Long Optical Resonator

    by Aisling Johnson, Martin Blaha, Alexander E. Ulanov, Arno Rauschenbeutel, Philipp Schneeweiss, Jürgen Volz

    We report on the observation of collective superstrong coupling of a small ensemble of atoms interacting with the field of a 30-m long fiber resonator containing a nanofiber section. The collective light-matter coupling strength exceeds the free-spectral range and the atoms couple to consecutive longitudinal resonator modes. The measured transmission spectra of the coupled atom-resonator system provide evidence of this regime, realized with a few hundred atoms with an intrinsic single-atom cooperativity of 0.13. These results are the starting point for studies in a new setting of light-matter interaction, with strong quantum nonlinearities and a new type of dynamics.

    Cited by 59
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    Monitoring squeezed collective modes of a one-dimensional Bose gas after an interaction quench using density-ripple analysis

    by Max Schemmer, Aisling Johnson, Isabelle Bouchoule

    We investigate the out-of-equilibrium dynamics following a sudden quench of the interaction strength in a one-dimensional quasicondensate trapped at the surface of an atom chip. Within a linearized approximation, the system is described by independent collective modes and the quench squeezes the phase-space distribution of each mode, leading to a subsequent breathing of each quadrature. We show that the collective modes are resolved by the power spectrum of density ripples which appear after a short time of flight. This allows us to experimentally probe the expected breathing phenomenon. Our results are in good agreement with theoretical predictions which take the longitudinal harmonic confinement into account.

    Cited by 74
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    Long-lived nonthermal states realized by atom losses in one-dimensional quasicondensates

    by A. Johnson, S. S. Szigeti, M. Schemmer, I. Bouchoule

    We investigate the cooling produced by a loss process nonselective in energy on a one-dimensional (1D) Bose gas with repulsive contact interactions in the quasicondensate regime. By performing nonlinear classical-field calculations for a homogeneous system, we show that the gas reaches a nonthermal state where different modes have acquired different temperatures. After losses have been turned off, this state is robust with respect to the nonlinear dynamics, described by the Gross-Pitaevskii equation. We argue that the integrability of the Gross-Pitaevskii equation is linked to the existence of such long-lived nonthermal states and illustrate this by showing that such states are not supported within a nonintegrable model of two coupled 1D gases of different masses. We go beyond a classical-field analysis, taking into account the quantum noise introduced by the discreteness of losses, and show that the nonthermal state is still produced and its nonthermal character is even enhanced. Finally, we extend the discussion to gases trapped in a harmonic potential and present experimental observations of a long-lived nonthermal state within a trapped 1D quasicondensate following an atom-loss process.

    Cited by 84
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    Monte Carlo wave-function description of losses in a one-dimensional Bose gas and cooling to the ground state by quantum feedback

    by M. Schemmer, A. Johnson, R. Photopoulos, I. Bouchoule

    The effect of atom losses on a homogeneous one-dimensional Bose gas lying within the quasicondensate regime is investigated using a Monte Carlo wave-function approach. The evolution of the system is calculated, conditioned by the loss sequence, namely, the times of individual losses and the position of the removed atoms. We describe the gas within the linearized Bogoliubov approach. For each mode, we find that, for a given quantum trajectory, the state of the system converges towards a coherent state, i.e., the ground state, displaced in phase space. We show that, provided losses are recorded with a temporal and spatially resolved detector, quantum feedback can be implemented and cooling to the ground state of one or several modes can be realized.

    Cited by 44
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    Momentum-Space Correlations of a One-Dimensional Bose Gas

    by Bess Fang, Aisling Johnson, Tommaso Roscilde, Isabelle Bouchoule

    Analyzing the noise in the momentum profiles of single realizations of one-dimensional Bose gases, we present the experimental measurement of the full momentum-space density correlations ⟨δnpδnp′⟩, which are related to the two-body momentum correlation function. Our data span the weakly interacting region of the phase diagram, going from the ideal Bose gas regime to the quasicondensate regime. We show experimentally that the bunching phenomenon, which manifests itself as super-Poissonian local fluctuations in momentum space, is present in all regimes. The quasicondensate regime is, however, characterized by the presence of negative correlations between different momenta, in contrast to the Bogolyubov theory for Bose condensates, predicting positive correlations between opposite momenta. Our data are in good agreement with ab initio calculations.

    Cited by 96
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