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Coupling between environment and ultrastrongly interacting composite system

Motoaki Bamba, Tetsuo Ogawa

Published Jun 10, 2013• 0 citations
OpenAlex

Abstract

When the light interacts with matters in a lossy cavity, in the standard cavity quantum electrodynamics, the dissipation of cavity fields is characterized simply by the strengths of the two couplings: the light-matter interaction and the system-environment coupling through the cavity mirror. However, in the ultrastrong light-matter interaction regime, the dissipation depends also on whether the two couplings are mediated by the electric field or the magnetic one (capacitive or inductive in superconducting circuits). Even if we know correctly the microscopic mechanism (Lagrangian) of the system-environment coupling, the coupling Hamiltonian itself is in principle modified due to the ultrastrong interaction in the cavity. In this paper, we show a recipe for deriving a general expression of the Hamiltonian of the system-environment coupling, which is applicable even in the ultrastrong light-matter interaction regime in the good-cavity and independent-transition limit.

Related papers

Recipe for the Hamiltonian of system-environment coupling applicable to the ultrastrong-light-matter-interaction regime

Motoaki Bamba, Tetsuo Ogawa

When the light interacts with matters in a lossy cavity, in the standard cavity quantum electrodynamics, the dissipation of cavity fields is characterized simply by the strengths of the two couplings: the light-matter interaction and the system-environment coupling through the cavity mirror. However, in the ultrastrong-light-matter-interaction regime, the dissipation depends also on whether the two couplings are mediated by the electric field or the magnetic one (capacitive or inductive in superconducting circuits). Even if we know correctly the microscopic mechanism (Lagrangian) of the system-environment coupling, the coupling Hamiltonian itself is in principle modified due to the ultrastrong interaction in the cavity. In this paper, we show a recipe for deriving a general expression of the Hamiltonian of the system-environment coupling, which is applicable even in the ultrastrong-light-matter-interaction regime in the good-cavity and independent-transition limits.

arXiv:1306.2099•Physical Review A•Feb 13, 2014•47 citations

System-environment coupling derived by Maxwell's boundary conditions from the weak to the ultrastrong light-matter-coupling regime

Motoaki Bamba, Tetsuo Ogawa

In the standard theory of cavity quantum electrodynamics (QED), coupling between photons inside and outside a cavity (cavity system and environment) is given conserving the total number of photons. However, when the cavity photons (ultrastrongly) interact with atoms or excitations in matters, the system-environment coupling must be determined from a more fundamental viewpoint. Based on the Maxwell's boundary conditions in the QED theory for dielectric media, we derive the quantum Langevin equation and input-output relation, in which the total number of polaritons (not photons) inside the cavity and photons outside is conserved.

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Reply to “Comment on ‘System-environment coupling derived by Maxwell's boundary conditions from the weak to the ultrastrong light-matter-coupling regime’ ”

Motoaki Bamba, Tetsuo Ogawa

As mentioned by De Liberato [Phys. Rev. A 89, 017801 (2014)], when we suppose the metallic thin mirror and perform the renormalization to the approach starting from the frequently used system-environment-coupling Hamiltonian, we can certainly resolve the discrepancy of its result from that obtained by the reliable approach in the main discussion of our paper [Phys. Rev. A 88, 013814 (2013)]. Although the suggested approach is currently applicable to the specific situation after checking its validity by our reliable but cumbersome approach, we instead propose to start from the system-environment-coupling Hamiltonian determined properly by the mechanism of the confinement and loss of the cavity fields. This approach is applicable to any cavity structure, in principle, and we do not face the renormalization problem appearing in the Comment.

arXiv:1311.1564•Physical Review A•Jan 6, 2014•4 citations

Comment on “System-environment coupling derived by Maxwell's boundary conditions from the weak to the ultrastrong light-matter-coupling regime”

Simone De Liberato

In a recent paper, Bamba and Ogawa [Phys. Rev. A 88, 013814 (2013)] developed a microscopic model describing a photonic cavity coupled to an excitonlike resonance. One of the results they obtained studying such a model is that, in the ultrastrong coupling regime, dissipation rates calculated applying the rotating-wave approximation on the system-environment coupling qualitatively differ from the ones calculated using a microscopic theory based on the quantum electrodynamics for dielectric media. Here I show that this result is an artifact, caused by an inconsistent application of the rotating-wave approximation and by an unphysical parameter choice.

arXiv:1307.5615•Physical Review A•Jan 6, 2014•20 citations

Dissipation and ultrastrong coupling in circuit QED

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Cavity and circuit QED study light-matter interaction at its most fundamental level. Yet, this interaction is most often neglected when considering the coupling of this system with an environment. In this paper, we show how this simplification, which leads to the standard quantum optics master equation, is at the root of unphysical effects. Including qubit relaxation and dephasing, and cavity relaxation, we derive a master equation that takes into account the qubit-resonator coupling. Special attention is given to the ultrastrong coupling regime, where the failure of the quantum optical master equation is manifest. In this situation, our model predicts an asymmetry in the vacuum Rabi splitting that could be used to probe dephasing noise at unexplored frequencies. We also show how fluctuations in the qubit frequency can cause sideband transitions, squeezing, and Casimir-like photon generation.

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Thermal emission in the ultrastrong-coupling regime

A. Ridolfo, M Leib, Salvatore Savasta +1 more

We have studied the thermal emission of a cavity quantum electrodynamic system in the ultrastrong-coupling regime, where the atom–cavity coupling rate becomes comparable with the cavity resonance frequency. In this regime, the standard descriptions of photodetection and dissipation fail. By following an approach that was recently put forward by Ridolfo et al (2012 Phys. Rev. Lett. 109 193602), we were able to calculate the emission of systems with arbitrary strength of light–matter interaction, by expressing the electric-field operator in the cavity–emitter dressed basis. In this paper, we present thermal photoluminescence spectra, calculated for given temperatures and for different couplings, in particular, for available circuit quantum electrodynamics parameters.

arXiv:1210.2318•Physica Scripta•Mar 1, 2013•5 citations
When the light interacts with matters in a lossy cavity, in the standard cavity quantum electrodynamics, the dissipation of cavity fields is characterized simply by the strengths of the two couplings: the light-matter interaction and the system-environment coupling through the cavity mirror. However, in the ultrastrong light-matter interaction regime, the dissipation depends also on whether the two couplings are mediated by the electric field or the magnetic one (capacitive or inductive in superconducting circuits). Even if we know correctly the microscopic mechanism (Lagrangian) of the system-environment coupling, the coupling Hamiltonian itself is in principle modified due to the ultrastrong interaction in the cavity. In this paper, we show a recipe for deriving a general expression of the Hamiltonian of the system-environment coupling, which is applicable even in the ultrastrong light-matter interaction regime in the good-cavity and independent-transition limit.
When the light interacts with matters in a lossy cavity, in the standard cavity quantum electrodynamics, the dissipation of cavity fields is characterized simply by the strengths of the two couplings: the light-matter interaction and the system-environment coupling through the cavity mirror. However, in the ultrastrong-light-matter-interaction regime, the dissipation depends also on whether the two couplings are mediated by the electric field or the magnetic one (capacitive or inductive in superconducting circuits). Even if we know correctly the microscopic mechanism (Lagrangian) of the system-environment coupling, the coupling Hamiltonian itself is in principle modified due to the ultrastrong interaction in the cavity. In this paper, we show a recipe for deriving a general expression of the Hamiltonian of the system-environment coupling, which is applicable even in the ultrastrong-light-matter-interaction regime in the good-cavity and independent-transition limits.
In the standard theory of cavity quantum electrodynamics (QED), coupling between photons inside and outside a cavity (cavity system and environment) is given conserving the total number of photons. However, when the cavity photons (ultrastrongly) interact with atoms or excitations in matters, the system-environment coupling must be determined from a more fundamental viewpoint. Based on the Maxwell's boundary conditions in the QED theory for dielectric media, we derive the quantum Langevin equation and input-output relation, in which the total number of polaritons (not photons) inside the cavity and photons outside is conserved.
As mentioned by De Liberato [Phys. Rev. A 89, 017801 (2014)], when we suppose the metallic thin mirror and perform the renormalization to the approach starting from the frequently used system-environment-coupling Hamiltonian, we can certainly resolve the discrepancy of its result from that obtained by the reliable approach in the main discussion of our paper [Phys. Rev. A 88, 013814 (2013)]. Although the suggested approach is currently applicable to the specific situation after checking its validity by our reliable but cumbersome approach, we instead propose to start from the system-environment-coupling Hamiltonian determined properly by the mechanism of the confinement and loss of the cavity fields. This approach is applicable to any cavity structure, in principle, and we do not face the renormalization problem appearing in the Comment.
In a recent paper, Bamba and Ogawa [Phys. Rev. A 88, 013814 (2013)] developed a microscopic model describing a photonic cavity coupled to an excitonlike resonance. One of the results they obtained studying such a model is that, in the ultrastrong coupling regime, dissipation rates calculated applying the rotating-wave approximation on the system-environment coupling qualitatively differ from the ones calculated using a microscopic theory based on the quantum electrodynamics for dielectric media. Here I show that this result is an artifact, caused by an inconsistent application of the rotating-wave approximation and by an unphysical parameter choice.
Cavity and circuit QED study light-matter interaction at its most fundamental level. Yet, this interaction is most often neglected when considering the coupling of this system with an environment. In this paper, we show how this simplification, which leads to the standard quantum optics master equation, is at the root of unphysical effects. Including qubit relaxation and dephasing, and cavity relaxation, we derive a master equation that takes into account the qubit-resonator coupling. Special attention is given to the ultrastrong coupling regime, where the failure of the quantum optical master equation is manifest. In this situation, our model predicts an asymmetry in the vacuum Rabi splitting that could be used to probe dephasing noise at unexplored frequencies. We also show how fluctuations in the qubit frequency can cause sideband transitions, squeezing, and Casimir-like photon generation.
We have studied the thermal emission of a cavity quantum electrodynamic system in the ultrastrong-coupling regime, where the atom–cavity coupling rate becomes comparable with the cavity resonance frequency. In this regime, the standard descriptions of photodetection and dissipation fail. By following an approach that was recently put forward by Ridolfo et al (2012 Phys. Rev. Lett. 109 193602), we were able to calculate the emission of systems with arbitrary strength of light–matter interaction, by expressing the electric-field operator in the cavity–emitter dressed basis. In this paper, we present thermal photoluminescence spectra, calculated for given temperatures and for different couplings, in particular, for available circuit quantum electrodynamics parameters.