Gauge freedom, quantum measurements, and time-dependent interactions in cavity QED

Settineri, Alessio; Stefano, Omar Di; Zueco, David; Hughes, Stephen; Savasta, Salvatore; Nori, Franco

doi:10.1103/physrevresearch.3.023079

Cited by 35 publications

(33 citation statements)

References 74 publications

(120 reference statements)

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“…Of course, the different representations provide the same energy levels for the lightmatter system. They also provide identical expectation values if operators and quantum states are both properly transformed [62]. We observe that the operators â and â † satisfy the same commutation relations of the bosonic operators â and â † .…”

Section: B Quantum Rabi Model In the Dipole Gaugementioning

confidence: 73%

“…In particular, the canonical momenta of the matter field differ from the kinetic momenta (see, e.g., Ref. [62]). Hence, this gauge is not the more convenient one to study the qubit properties.…”

Section: Discussionmentioning

confidence: 99%

“…( 13), clearly we see that the photon operators are not gauge invariant. Thus, in order to obtain correct results in the dipole gauge [62], it is essential to properly take into account how these operators change under the Û -transformation [see Eq. ( 13)].…”

Section: B Quantum Rabi Model In the Dipole Gaugementioning

confidence: 99%

“…Indeed, in this regime, all the transition frequencies tend to become flat, equally spaced, and two-by-two quasi-degenerate. Theoretical analysis [62] shows that, beyond the DSC regime, the quasi-degenerate light-matter eigenstates tend to factorize as |n, g and |n, e , so that the system tends to decouple from the qubit reservoir (Γ q kj → 0) and cannot be significantly excited. Specifically, the matrix elements j|σ x |k are different from zero only for states such that ω kj → 0.…”

Section: A Zero Cavity-qubit Detuningmentioning

confidence: 99%

“…Recently, some gauge issues have been solved. In particular, it has been shown how to obtain the correct quantum Rabi and Dicke Hamiltonians in the Coulomb gauge [59][60][61][62]. It has also been shown how to derive a gauge-invariant master equation and obtain gaugeinvariant emission spectra [63].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Regimes of Cavity-QED under Incoherent Excitation: From Weak to Deep Strong Coupling

Mercurio¹,

Macrì²,

Gustin³

et al. 2021

Preprint

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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) the appears 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 occurence of light-matter decoupling in the deep strong coupling regime, and show how all of the obtained results are gauge invariant.

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Section: B Quantum Rabi Model In the Dipole Gaugementioning

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: B Quantum Rabi Model In the Dipole Gaugementioning

confidence: 99%

Section: A Zero Cavity-qubit Detuningmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Regimes of Cavity-QED under Incoherent Excitation: From Weak to Deep Strong Coupling

Mercurio¹,

Macrì²,

Gustin³

et al. 2021

Preprint

Self Cite

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Theoretical Advances in Polariton Chemistry and Molecular Cavity Quantum Electrodynamics

et al. 2023

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When molecules are coupled to an optical cavity, new light–matter hybrid states, so-called polaritons, are formed due to quantum light–matter interactions. With the experimental demonstrations of modifying chemical reactivities by forming polaritons under strong light–matter interactions, theorists have been encouraged to develop new methods to simulate these systems and discover new strategies to tune and control reactions. This review summarizes some of these exciting theoretical advances in polariton chemistry, in methods ranging from the fundamental framework to computational techniques and applications spanning from photochemistry to vibrational strong coupling. Even though the theory of quantum light–matter interactions goes back to the midtwentieth century, the gaps in the knowledge of molecular quantum electrodynamics (QED) have only recently been filled. We review recent advances made in resolving gauge ambiguities, the correct form of different QED Hamiltonians under different gauges, and their connections to various quantum optics models. Then, we review recently developed ab initio QED approaches which can accurately describe polariton states in a realistic molecule–cavity hybrid system. We then discuss applications using these method advancements. We review advancements in polariton photochemistry where the cavity is made resonant to electronic transitions to control molecular nonadiabatic excited state dynamics and enable new photochemical reactivities. When the cavity resonance is tuned to the molecular vibrations instead, ground-state chemical reaction modifications have been demonstrated experimentally, though its mechanistic principle remains unclear. We present some recent theoretical progress in resolving this mystery. Finally, we review the recent advances in understanding the collective coupling regime between light and matter, where many molecules can collectively couple to a single cavity mode or many cavity modes. We also lay out the current challenges in theory to explain the observed experimental results. We hope that this review will serve as a useful document for anyone who wants to become familiar with the context of polariton chemistry and molecular cavity QED and thus significantly benefit the entire community.

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Cavity-field distribution in multiphoton Jaynes-Cummings resonances

Mavrogordatos

2021

Phys. Rev. A

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We explore the statistical behaviour of the light emanating from a coherently driven Jaynes-Cummings (JC) oscillator operating in the regime of multiphoton blockade with two monitored output channels causing the loss of coherence at equal rates. We do so by adopting an operational approach which draws the particle and wave aspects of the forwards scattered radiation together, building upon the relationship between quantum optical correlation functions and conditional measurements. We first derive an analytical expression of the intensity cross-correlation function at the peak of the two-photon JC resonance to demonstrate the breakdown of detailed balance. The application of quantum trajectory theory in parallel with the quantum regression formula subsequently uncovers various aspects of temporal asymmetry in the quantum fluctuations characterizing the cascaded process through which a multiphoton resonance is established and read out. We find that monitoring different quadratures of the cavity field in conditional homodyne detection affects the times waited between successive photon counter "clicks", which in turn trigger the sampling of the homodyne current. Despite the fact that the steady-state cavity occupation is of the order of a photon, monitoring of the developing bimodality also impacts on the ratio between the emissions directed along the two decoherence channels.

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Gauge freedom, quantum measurements, and time-dependent interactions in cavity QED

Cited by 35 publications

References 74 publications

Regimes of Cavity-QED under Incoherent Excitation: From Weak to Deep Strong Coupling

Regimes of Cavity-QED under Incoherent Excitation: From Weak to Deep Strong Coupling

Theoretical Advances in Polariton Chemistry and Molecular Cavity Quantum Electrodynamics

Cavity-field distribution in multiphoton Jaynes-Cummings resonances

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