1,985 research outputs found
Lasing from dressed dots
No full textA theoretical analysis of asymmetric dressed quantum dots in a photonic crystal cavity suggests that the system could form a new type of solid-state terahertz laser. However, an experimental realization will likely require advances in fabrication technology
Data underpinning - Excitonic spectral features in strongly-coupled organic polaritons
No full textRealted article:
Cwik, J. A., Kirton, P., De Liberato, S., & Keeling, J. (2016). Excitonic spectral features in strongly-coupled organic polaritons. Physical Review A, 93(33840), 1-12. https://doi.org/10.1103/PhysRevA.93.033840</span
Electro-optical sampling of quantum vacuum fluctuations in dispersive dielectrics
No full textElectro-optical sampling has been recently used to perform spectrally-resolved measurements of electromagnetic vacuum fluctuations and it has been predicted it could be used to probe the population of virtual photons predicted to exist in the ground state of an ultrastrongly light-matter coupled system. In order to understand which information on the ground state of an interacting system can be acquired thanks to this technique, in this paper we will develop the quantum theory of electro-optical sampling in arbitrary dispersive dielectrics. Our theory shows that a measure of the time correlations of the vacuum fluctuations effectively implements an ellipsometry measurement on the quantum vacuum, allowing to access the frequency-dependent dielectric function without the need of any resonant incoming photon. We discuss consequences of these results on the possibility to use electro-optical sampling to access the virtual photon population
Open quantum systems with local and collective incoherent processes: Efficient numerical simulations using permutational invariance
No full textThe permutational invariance of identical two-level systems allows for an exponential reduction in the computational resources required to study the Lindblad dynamics of coupled spin-boson ensembles evolvingunder the effect of both local and collective noise. Here we take advantage of this speedup to study several important physical phenomena in the presence of local incoherent processes, in which each degree of freedomcouples to its own reservoir. Assessing the robustness of collective effects against local dissipation is paramount to predict their presence in different physical implementations. We have developed an open-source library inPYTHON, the Permutational-Invariant Quantum Solver (PIQS), which we use to study a variety of phenomena in driven-dissipative open quantum systems. We consider both local and collective incoherent processes in theweak-, strong-, and ultrastrong-coupling regimes. Using PIQS, we reproduce a series of known physical results concerning collective quantum effects and extend their study to the local driven-dissipative scenario. Our workaddresses the robustness of various collective phenomena, e.g., spin squeezing, superradiance, and quantum phase transitions, against local dissipation processes
Light-matter decoupling in the deep strong coupling regime: the breakdown of the Purcell Effect
No full textImprovements in both the photonic confinement and the emitter design have led to a steady increase in the strength of the light-matter coupling in cavity quantum electrodynamics experiments. This has allowed us to access interaction-dominated regimes in which the state of the system can only be described in terms of mixed light-matter excitations. Here we show that, when the coupling between light and matter becomes strong enough, this picture breaks down, and light and matter degrees of freedom totally decouple. A striking consequence of such a counterintuitive phenomenon is that the Purcell effect is reversed and the spontaneous emission rate, usually thought to increase with the light-matter coupling strength, plummets instead for large enough couplings
Virtual photons in the ground state of a dissipative system
No full textMuch of the novel physics predicted to be observable in the ultrastrong light-matter coupling regime rests on the hybridisation between states with different numbers of excitations, leading to a population of virtual photons in the system’s ground state. In this article, exploiting an exact diagonalization approach, we derive both analytical and numerical results for the population of virtual photons in presence of arbitrary losses. Specialising our results to the case of Lorentzian resonances we then show that the virtual photon population is only quantitatively affected by losses, even when those become the dominant energy scale. Our results demonstrate most of the ultrastrong-coupling phenomenology can be observed in loss-dominated systems which are not even in the standard strong coupling regime. We thus open the possibility to investigate ultrastrong-coupling physics to platforms that were previously considered unsuitable due to their large losses.<br/
Exact solution of polaritonic systems with arbitrary light and matter frequency-dependent losses
No full textIn this paper we perform the exact diagonalization of a light-matter strongly
coupled system taking into account arbitrary losses via both energy dissipation
in the optically active material and photon escape out of the resonator. This
allows to naturally treat the cases of couplings with structured reservoirs,
which can strongly impact the polaritonic response via frequency-dependent
losses or discrete-to-continuum strong coupling. We discuss the emergent gauge
freedom of the resulting theory and provide analytical expressions for all the
gauge-invariant observables both in the Power-Zienau-Woolley and the Coulomb
representations. In order to exemplify the results the theory is finally
specialised to two specific cases. In the first one both light and matter
resonances are characterised by Lorentzian linewidths, and in the second one a
fixed absorption band is also present. The analytical expressions provided in
this paper can be used to predict, fit, and interpret results from polaritonic
experiments with arbitrary values of the light-matter coupling and with losses
of arbitrary intensity and spectral shape, in both the light and matter
channels
Laser‑stabilised ionising transitions
No full textStabilising atoms exposed to intense laser fields has been a central topic in atomic physics for decades, inspiring several theoretical frameworks that describe the phenomenon under different resonance conditions and coupling regimes. Here we theoretically investigate an ionising electronic transition driven by a resonant pump field, in contrast to Kramers–Henneberger atoms, which are stabilised by non-perturbative, non-resonant laser pulses. We show that, above a critical pump intensity, the drive creates a novel metastable electronic bound state embedded in the continuum, which decays via two-photon ionisation. We calculate the resulting resonant fluorescence spectrum and find a qualitatively different structure from the familiar Mollow triplet associated with bound-to-bound transitions. This fluorescence provides a time-resolved probe of the population of the metastable state. In analogy to how the AC Stark shift is a semiclassical counterpart of the single-photon Rabi splitting observed in optical cavities, the phenomenon we describe is best understood as a semiclassical analogue of recently observed excitons bound by a single cavity photon
Polaritonics: From microcavities to sub-wavelength confinement
No full textFollowing the initial success of cavity quantum electrodynamics in atomic systems, strong coupling between light and matter excitations is now achieved in several solid-state set-ups. In those systems, the possibility to engineer quantum emitters and resonators with very different characteristics has allowed access to novel nonlinear and non-perturbative phenomena of both fundamental and applied interest. In this article, we will review some advances in the field of solid-state cavity quantum electrodynamics, focussing on the scaling of the relevant figures of merit in the transition from microcavities to sub-wavelength confinement.</p
Strong light-matter coupling in microcavities characterised by Rabi-splittings comparable to the Bragg stop-band widths
No full textThe vacuum Rabi splitting of polaritonic eigenmodes in semiconductor microcavities scales with the square root of the oscillator strength, as predicted by the coupled oscillator model and confirmed in many experiments. We show here that the square root law is no more applicable if the Rabi splitting becomes comparable or larger than the stop-band width of the Bragg mirrors forming the cavity. Once the oscillator strength becomes large enough, the material hosting excitons hybridises with the quasi-continuum microcavity Bragg modes lying outside of the stop-band, thus forming a novel kind of polaritonic resonance. We study this physics considering both two- and three-dimensional excitonic materials embedded in the microcavity. We highlight the varied phenomenology of those polaritons and develop a theoretical understanding of their most peculiar features
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