Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Laser in ultrastrong light-matter coupling regime

Motoaki Bamba, Tetsuo Ogawa

Published Oct 15, 2014• 0 citations
OpenAlex

Abstract

In ultrastrong light-matter coupling regime, it is found theoretically that lasing accompanies odd-order harmonics of radiation field both inside and outside the cavity and even-order harmonics of atomic population. This qualitative difference from the normal laser is generally obtained independent of whether we choose the Coulomb gauge or the electric-dipole one, although quantitative behaviors strongly depend on the gauge choice due to the two-level and single-mode approximations used in our calculation. The lasing also shows a bistability for strong enough light-matter coupling and low enough cavity loss.

Related papers

Laser under ultrastrong light-matter interaction: Qualitative aspects and quantitative influences by level and mode truncations

Motoaki Bamba, Tetsuo Ogawa

We investigate theoretically the light amplification by stimulated emission of radiation (laser) in the ultrastrong light-matter interaction regime under the two-level and single-mode approximations. The conventional picture of the laser is broken under the ultrastrong interaction. Instead, we must explicitly discuss the dynamics of the electric field and of the magnetic one distinctively, which make the ``laser'' qualitatively different from the conventional laser. We found that the laser generally accompanies odd-order harmonics of the electromagnetic fields both inside and outside the cavity and a synchronization with an oscillation of atomic population. A bistability is also demonstrated. However, since our model is quite simplified, we got quantitatively different results from the Hamiltonians in the velocity and length forms of the light-matter interaction, while the appearance of the multiple harmonics and the bistability is qualitatively reliable.

arXiv:1410.3912•Physical Review A•Mar 7, 2016•13 citations

Breakdown of gauge invariance in ultrastrong-coupling cavity QED

Daniele De Bernardis, Philipp Pilar, Tuomas Jaako +2 more

We revisit the derivation of Rabi- and Dicke-type models, which are commonly used for the study of quantum light-matter interactions in cavity and circuit QED. We demonstrate that the validity of the two-level approximation, which is an essential step in this derivation, depends explicitly on the choice of gauge once the system enters the ultrastrong-coupling regime. In particular, while in the electric dipole gauge the two-level approximation can be performed as long as the Rabi frequency remains much smaller than the energies of all higher-lying levels, it can dramatically fail in the Coulomb gauge, even for systems with an extremely anharmonic spectrum. We extensively investigate this phenomenon both in the single-dipole (Rabi) and multidipole (Dicke) case, and consider the specific examples of dipoles confined by double-well and square-well potentials, and of circuit QED systems with flux qubits coupled to an LC resonator.

arXiv:1805.05339•Physical Review A•Nov 13, 2018•182 citations

A one-atom laser in a regime of strong coupling

Jason McKeever, Andreea Boca, A. David. Boozer +2 more

Although conventional lasers operate with a large number of intracavity atoms, the lasing properties of a single atom in a resonant cavity have been theoretically investigated for more than a decade. Here we report the experimental realization of such a one-atom laser operated in a regime of strong coupling. Our experiment exploits recent advances in cavity quantum electrodynamics that allow one atom to be isolated in an optical cavity in a regime for which one photon is sufficient to saturate the atomic transition. In this regime the observed characteristics of the atom-cavity system are qualitatively different from those of the familiar many atom case. Specifically, we present measurements of intracavity photon number versus pump intensity that exhibit "thresholdless" behavior, and infer that the output flux from the cavity mode exceeds that from atomic fluorescence by more than tenfold. Observations of the second-order intensity correlation function demonstrate that our one-atom laser generates manifestly nonclassical light that exhibits both photon antibunching and sub-Poissonian photon statistics.

arXiv:quant-ph/0309199•Frontiers in Optics•Jan 1, 2003•2 citations

Lasing in the superradiant crossover regime

Kamanasish Debnath, Yuan Zhang, Klaus Mølmer

A new class of laser, which harnesses coherence in both light and atoms, is possible with ultracold alkaline-earth-metal atoms trapped in an optical lattice inside an optical cavity. Different lasing regimes, including superradiance, superradiant, and conventional lasing, are distinguished by the relative coherence stored in the atoms and in the cavity mode. We analyze the physics in two different experimentally achievable regions of the superradiant lasing regime. Our calculations confirm the narrow linewidth of superradiant lasing for the doubly forbidden clock transition ${}^{3}{P}_{0}\ensuremath{\rightarrow}{}^{1}{S}_{0}$ of $^{87}\mathrm{Sr}$ atoms. Under strong driving of the dipole-forbidden transition ${}^{3}{P}_{1}\ensuremath{\rightarrow}{}^{1}{S}_{0}$ of $^{88}\mathrm{Sr}$ atoms, the superradiant linewidth narrows further due to the coherent excitation of the cavity field.

arXiv:1809.01602•Physical Review A•Dec 26, 2018•65 citations

Regimes of cavity QED under incoherent excitation: From weak to deep strong coupling

Alberto Mercurio, Vincenzo Macrí, Chris Gustin +3 more

The prototypical system constituted by a two-level atom interacting with a quantized single-mode electromagnetic field is described by the quantum Rabi model (QRM). The QRM is potentially valid at any light-matter interaction regime, ranging from the weak (where the decay rates exceeds the coupling rate) to the deep strong coupling (where the interaction rate exceeds the bare transition frequencies of the subsystems). However, when reaching the ultrastrong coupling regime, several theoretical issues may prevent the correct description of the observable dynamics of such a system: (i) the standard quantum optics master equation fails to correctly describe the interaction of this system with the reservoirs; (ii) the correct output photon rate is no longer proportional to the intracavity photon number; and (iii) they appear to violate gauge invariance. Here, we study the photon flux emission rate of this system under the incoherent excitation of the two-level atom for any light-matter interaction strength and consider different effective temperatures. The dependence of the emission spectra on the coupling strength is the result of the interplay between energy levels, matrix elements of the observables, and the density of states of the reservoirs. Within this approach, we also study the occurrence of light-matter decoupling in the deep strong-coupling regime and show how all of the obtained results are gauge invariant.

arXiv:2112.08917•Physical Review Research•Apr 20, 2022•25 citations

Umklapp Lasing with a Quantum Degenerate Fermi Gas

Francesco Piazza, Philipp Strack

Lasing [1, 2] and superradiance [3‐5] phenomena are currently enjoying a renaissance as research topics in atomic physics. Fundamentally based on the interaction of matter with an electromagnetic (light) field, the atomic dipoles in a “lasing medium” collectively emit into selected modes of the electromagnetic field and thereby create an amplified and coherent source of light. Present-day lasers use di erent types of gain media and cover a wide range of output frequencies for application in both, fundamental research and industry. A recent string of papers has reported on superradiance [6, 7] and lasing-type instabilities using Bose gases of various type (thermal atoms [8, 9], photon gases [10] and Bose-Einstein condensed atoms [11‐14]) in optical cavities. Buoyed by experimental control over essentially single excitation quanta of atoms and photons [15‐19] in cavity quantum electrodynamics, these works o er intriguing prospects for the next wave of experiments on strongly interacting light-mattter systems including a new regime where unexpected many-body and quantum fluctuation e ects of the lasing medium may become visible. Bohnet et al. [20] recently operated a superradiant “bad-cavity” laser in the few-photon regime based on coherent oscillations of the inter-atomic, collective dipole of the ultracold atoms in the cavity [21]. In this paper, we point out that a quantum degenerate Fermi gas has remarkable features as a lasing medium in a transversally driven cavity as sketched in Fig. 1. We show that the quantum statistics of the Fermi gas puts the coupled cavity+atoms system generically close to superradiance threshold as a consequence of the Pauli exclusion principle (“Pauli pressure”). Physically, this arises from enhanced scattering of fermions between di erent points on the Fermi surface with radiusjkFj by exchanging relatively large photon momenta Q from the cavity as illustrated in Fig. 1. By changing the power of the pump laser at a given density of the Fermi gas, the lasing transition is concomitant with the spontaneous formation of a charge density wave oscillating with 1=Q in real space. Tuning the ratiojkFj=jQj allows to generate a cavity spectrum with “broadband light” in certain spectral ranges or, for energies outside the particle-hole continuum of the fermions, light with relatively narrow linewidth. The normal mode splitting of the cavity by a single atom is completely replaced by many-body Ω |kF| Q

•Sep 11, 2013•0 citations
In ultrastrong light-matter coupling regime, it is found theoretically that lasing accompanies odd-order harmonics of radiation field both inside and outside the cavity and even-order harmonics of atomic population. This qualitative difference from the normal laser is generally obtained independent of whether we choose the Coulomb gauge or the electric-dipole one, although quantitative behaviors strongly depend on the gauge choice due to the two-level and single-mode approximations used in our calculation. The lasing also shows a bistability for strong enough light-matter coupling and low enough cavity loss.
We investigate theoretically the light amplification by stimulated emission of radiation (laser) in the ultrastrong light-matter interaction regime under the two-level and single-mode approximations. The conventional picture of the laser is broken under the ultrastrong interaction. Instead, we must explicitly discuss the dynamics of the electric field and of the magnetic one distinctively, which make the ``laser'' qualitatively different from the conventional laser. We found that the laser generally accompanies odd-order harmonics of the electromagnetic fields both inside and outside the cavity and a synchronization with an oscillation of atomic population. A bistability is also demonstrated. However, since our model is quite simplified, we got quantitatively different results from the Hamiltonians in the velocity and length forms of the light-matter interaction, while the appearance of the multiple harmonics and the bistability is qualitatively reliable.
We revisit the derivation of Rabi- and Dicke-type models, which are commonly used for the study of quantum light-matter interactions in cavity and circuit QED. We demonstrate that the validity of the two-level approximation, which is an essential step in this derivation, depends explicitly on the choice of gauge once the system enters the ultrastrong-coupling regime. In particular, while in the electric dipole gauge the two-level approximation can be performed as long as the Rabi frequency remains much smaller than the energies of all higher-lying levels, it can dramatically fail in the Coulomb gauge, even for systems with an extremely anharmonic spectrum. We extensively investigate this phenomenon both in the single-dipole (Rabi) and multidipole (Dicke) case, and consider the specific examples of dipoles confined by double-well and square-well potentials, and of circuit QED systems with flux qubits coupled to an LC resonator.
Although conventional lasers operate with a large number of intracavity atoms, the lasing properties of a single atom in a resonant cavity have been theoretically investigated for more than a decade. Here we report the experimental realization of such a one-atom laser operated in a regime of strong coupling. Our experiment exploits recent advances in cavity quantum electrodynamics that allow one atom to be isolated in an optical cavity in a regime for which one photon is sufficient to saturate the atomic transition. In this regime the observed characteristics of the atom-cavity system are qualitatively different from those of the familiar many atom case. Specifically, we present measurements of intracavity photon number versus pump intensity that exhibit "thresholdless" behavior, and infer that the output flux from the cavity mode exceeds that from atomic fluorescence by more than tenfold. Observations of the second-order intensity correlation function demonstrate that our one-atom laser generates manifestly nonclassical light that exhibits both photon antibunching and sub-Poissonian photon statistics.
A new class of laser, which harnesses coherence in both light and atoms, is possible with ultracold alkaline-earth-metal atoms trapped in an optical lattice inside an optical cavity. Different lasing regimes, including superradiance, superradiant, and conventional lasing, are distinguished by the relative coherence stored in the atoms and in the cavity mode. We analyze the physics in two different experimentally achievable regions of the superradiant lasing regime. Our calculations confirm the narrow linewidth of superradiant lasing for the doubly forbidden clock transition ${}^{3}{P}_{0}\ensuremath{\rightarrow}{}^{1}{S}_{0}$ of 87Sr^{87}\mathrm{Sr}87Sr atoms. Under strong driving of the dipole-forbidden transition ${}^{3}{P}_{1}\ensuremath{\rightarrow}{}^{1}{S}_{0}$ of 88Sr^{88}\mathrm{Sr}88Sr atoms, the superradiant linewidth narrows further due to the coherent excitation of the cavity field.
The prototypical system constituted by a two-level atom interacting with a quantized single-mode electromagnetic field is described by the quantum Rabi model (QRM). The QRM is potentially valid at any light-matter interaction regime, ranging from the weak (where the decay rates exceeds the coupling rate) to the deep strong coupling (where the interaction rate exceeds the bare transition frequencies of the subsystems). However, when reaching the ultrastrong coupling regime, several theoretical issues may prevent the correct description of the observable dynamics of such a system: (i) the standard quantum optics master equation fails to correctly describe the interaction of this system with the reservoirs; (ii) the correct output photon rate is no longer proportional to the intracavity photon number; and (iii) they appear to violate gauge invariance. Here, we study the photon flux emission rate of this system under the incoherent excitation of the two-level atom for any light-matter interaction strength and consider different effective temperatures. The dependence of the emission spectra on the coupling strength is the result of the interplay between energy levels, matrix elements of the observables, and the density of states of the reservoirs. Within this approach, we also study the occurrence of light-matter decoupling in the deep strong-coupling regime and show how all of the obtained results are gauge invariant.
Lasing [1, 2] and superradiance [3‐5] phenomena are currently enjoying a renaissance as research topics in atomic physics. Fundamentally based on the interaction of matter with an electromagnetic (light) field, the atomic dipoles in a “lasing medium” collectively emit into selected modes of the electromagnetic field and thereby create an amplified and coherent source of light. Present-day lasers use di erent types of gain media and cover a wide range of output frequencies for application in both, fundamental research and industry. A recent string of papers has reported on superradiance [6, 7] and lasing-type instabilities using Bose gases of various type (thermal atoms [8, 9], photon gases [10] and Bose-Einstein condensed atoms [11‐14]) in optical cavities. Buoyed by experimental control over essentially single excitation quanta of atoms and photons [15‐19] in cavity quantum electrodynamics, these works o er intriguing prospects for the next wave of experiments on strongly interacting light-mattter systems including a new regime where unexpected many-body and quantum fluctuation e ects of the lasing medium may become visible. Bohnet et al. [20] recently operated a superradiant “bad-cavity” laser in the few-photon regime based on coherent oscillations of the inter-atomic, collective dipole of the ultracold atoms in the cavity [21]. In this paper, we point out that a quantum degenerate Fermi gas has remarkable features as a lasing medium in a transversally driven cavity as sketched in Fig. 1. We show that the quantum statistics of the Fermi gas puts the coupled cavity+atoms system generically close to superradiance threshold as a consequence of the Pauli exclusion principle (“Pauli pressure”). Physically, this arises from enhanced scattering of fermions between di erent points on the Fermi surface with radiusjkFj by exchanging relatively large photon momenta Q from the cavity as illustrated in Fig. 1. By changing the power of the pump laser at a given density of the Fermi gas, the lasing transition is concomitant with the spontaneous formation of a charge density wave oscillating with 1=Q in real space. Tuning the ratiojkFj=jQj allows to generate a cavity spectrum with “broadband light” in certain spectral ranges or, for energies outside the particle-hole continuum of the fermions, light with relatively narrow linewidth. The normal mode splitting of the cavity by a single atom is completely replaced by many-body Ω |kF| Q