Generic Cavity Research Articles

Can We Observe Nonperturbative Vacuum Shifts in Cavity QED?

We address the fundamental question of whether or not it is possible to achieve conditions under which the coupling of a single dipole to a strongly confined electromagnetic vacuum can result in nonperturbative corrections to the dipole's ground state. To do so we consider two simplified, but otherwise rather generic cavity QED setups, which allow us to derive analytic expressions for the total ground-state energy and to distinguish explicitly between purely electrostatic and genuine vacuum-induced contributions. Importantly, this derivation takes the full electromagnetic spectrum into account while avoiding any ambiguities arising from an adhoc mode truncation. Our findings show that while the effect of confinement perse is not enough to result in substantial vacuum-induced corrections, the presence of high-impedance modes, such as plasmons or engineered LC resonances, can drastically increase these effects. Therefore, we conclude that with appropriately designed experiments it is at least in principle possible to access a regime where light-matter interactions become nonperturbative.

Generation and manipulation of phonon lasering in a two-drive cavity magnomechanical system

A simple and feasible scheme for the generation and manipulation of phonon lasering is proposed and investigated based on a generic three-mode cavity magnomechanical system, in which a magnon mode couples simultaneously with a microwave cavity mode and a phonon mode. In sharp contrast to all previous phonon lasering schemes with only a single drive, the input pump field for the system in the proposed scheme is split into two microwave driving fields to drive the microwave cavity mode and the magnon mode, respectively. The impact of changing relative phase and relative amplitude ratio of the two microwave drives on mechanical gain, stimulated emitted phonon number, threshold power, and phonon emission line shape are theoretically and numerically investigated. The results indicate that the phonon laser action can be effectively controlled simply by adjusting the relative phase and relative amplitude ratio, so additional and tunable degrees of freedom are introduced to control the phonon laser. Considering the experimental feasibility of the generic cavity magnomechanical system and the two-drive approach, the present scheme provides a potentially practical route for the development of tunable phonon lasering devices with low-threshold, high-gain, and narrow-linewidth properties based on the platform of cavity magnomechanics.

Generation of time-frequency entangled photon pairs propagating in separate waveguides in circuit QED setup

Time-frequency entangled photons constitute an important resource for a plethora of applications across the diverse quantum technology landscape. Thus, efficient and tunable setups for the generation of entangled photons are requisite for modern quantum technologies. In this work, we propose a generic cavity QED setup designed for on-demand generation of time-frequency entangled photon pairs, with each photon propagating in a separate waveguide. We outline a potential incarnation of this setup in the microwave superconducting circuit QED architecture. We derive and numerically solve the set of equations of motion governing the evolution of the quantum state of the system, allowing us to examine the photon emission dynamics. Using the Schmidt decomposition of the joint spectral amplitude of the emitted photon pair, we compute the entanglement entropy analyzing its dependence on the system parameters. We outline the potential extension of the proposed scheme for the generation of multiphoton time-frequency entangled states.

Quantum entanglement and one-way steering in a cavity magnomechanical system via a squeezed vacuum field.

We propose a simple scheme to generate quantum entanglement and one-way steering between distinct mode pairs in a generic cavity magnomechanical system, which is composed of a microwave cavity and a yttrium iron garnet sphere supporting magnon and phonon modes. The microwave cavity is pumped by a weak squeezed vacuum field, which plays an important role for establishing quantum entanglement and steering. It is found that when the magnon mode is driven by the red-detuned laser, the maximum entanglement between cavity mode and phonon mode and the maximum phonon-to-photon one-way steering can be effectively generated via adjusting the ratio of two coupling rates. While under the much weaker magnomechanical coupling, the quantum entanglement and one-way steering between cavity mode and magnon mode can be achieved, where the steering direction is determined merely by the relative dissipation strength of the cavity to the magnon mode. More interestingly, we reveal that the robustness to the temperature for entanglement and steering between any mode pairs can be evidently enhanced by selecting the squeezing parameter appropriately.

Entanglement of microwave-optical modes in a strongly coupled electro-optomechanical system

Quantum transduction between microwave and optics can be realized by quantum teleportation if given reliable microwave-optical entanglement, namely entanglement-based quantum transduction. To realize this protocol, an entangled source with high-fidelity between the two frequencies is necessary. In this paper, we study the microwave and optical entanglement generation based on a generic cavity electro-optomechanical system in the strong coupling regime. Splittings are shown in the microwave and optical output spectra and the frequency entanglement between the two modes is quantified. We show that entanglement can be straightforwardly encoded in the frequency-bin degree of freedom and propose a feasible experiment to verify entangled photon pairs. The experimental implementation is systematically analyzed, and the preferable parameter regime for entanglement verification is identified. An inequality is given as a criterion for good entanglement verification with analysis of practical imperfections.

Realization of Directional Amplification in a Microwave Optomechanical Device

Directional transmission or amplification of microwave signals is indispensable in various applications involving sensitive measurements. In this work we show in experiment how to use a generic cavity optomechanical setup to non-reciprocally amplify microwave signals above 3 GHz in one direction by 9 decibels, and simultaneously attenuate the transmission in the opposite direction by 21 decibels. We use a device including two on-chip superconducting resonators and two metallic drumhead mechanical oscillators. Application of four microwave pump tone frequencies allows for designing constructive or destructive interference for a signal tone depending on the propagation direction. The device can also be configured as an isolator with a lossless nonreciprocal transmission and 18 dB of isolation.

Enhancing Cavity Quantum Electrodynamics via Antisqueezing: Synthetic Ultrastrong Coupling.

We present and analyze a method where parametric (two-photon) driving of a cavity is used to exponentially enhance the light-matter coupling in a generic cavity QED setup, with time-dependent control. Our method allows one to enhance weak-coupling systems, such that they enter the strong coupling regime (where the coupling exceeds dissipative rates) and even the ultrastrong coupling regime (where the coupling is comparable to the cavity frequency). As an example, we show how the scheme allows one to use a weak-coupling system to adiabatically prepare the highly entangled ground state of the ultrastrong coupling system. The resulting state could be used for remote entanglement applications.

On shock train interaction with cavity oscillations in a confined supersonic flow

The interaction between shock train and cavity flow oscillations has been investigated experimentally in an open jet facility. Mach 1.71 flow has been passed over a set of rectangular cavities with L/D ratios varying between 5 and 10. Unsteady pressure measurement and schlieren flow visualization is employed to gain insight into the flow physics. Flow visualization reveals the presence of shock train coupled shear layer oscillations at different levels. Confinement variation establishes the importance of cavity depth in affecting the shock train structure, as the increase in depth resulted in decrease in boundary layer thickness. Shock train strength is found to decrease with decrease in L/D and the weak shock system promotes development of generic cavity oscillations and flow features through longitudinal mechanism. The shock train is found to be oscillatory in nature and the mean position of the bifurcated shock shifts downstream with decrease in L/D. Large scale structures and strengthened oscillations increase the mean and RMS pressure level of the cavities respectively. These large scale structures are incoherent for cavities with hardly any oscillations and coherent for cavities with sustained oscillations. Mode switching and temporal variations in pressure fluctuations are absent for shock train coupled cavity oscillations.

Steady-state light-mechanical quantum steerable correlations in cavity optomechanics

Einstein-Podolsky-Rosen (EPR) steering is a quantum nonlocal effect which is intrinsically distinct from Bell nonlocality and quantum entanglement. In this paper, we investigate in detail the properties of steady-state light-mechanical Gaussian steerable correlations in a generic cavity optomechanical system. When considering the steering between the intracavity field and the mechanical oscillator, we find that under blue-detuned driving, the steady-state steering via optomechanical parametric downconversion is present in only one direction and, moreover, the steering direction is determined merely by the relative dissipation strength of the cavity to the mechanics. Furthermore, when considering the steering between the cavity output field and the mechanical oscillator, we reveal that under red-detuned driving, strong steering can be achieved in the sideband-unresolved regime for a filtered output field with given central frequency and bandwidth. This steering with the output field can also be present in one way by adjusting the driving strength and exists up to the environment temperature $T\ensuremath{\approx}10$ K for the parameters close to those in the recent experiments. Finally, we show that the achieved strong light-mechanical correlations can be explored to realize macroscopic EPR steering of two distant optomechanical oscillators in the regime of unresolved sidebands via entanglement swapping.

Photonic-assisted diagnosis of electromagnetic coupling into a generic object

A photonic-assisted probing system to diagnose the electromagnetic influences of an electronic subsystem against intense electronic threat is presented. The shielding effectiveness of a generic missile and the coupled fields into the missile cavity were investigated by a fiber-coupled electro-optic field probe with its associated photonic system. To characterize the absolute field strength in the cavity, the probe was calibrated with a standard gain horn antenna at the R band by generating known fields toward the generic object. The fields coupled into the metallic cavity can be resonantly built up at multiple frequencies over a power range of 32 dB. The measured resonance characteristics of the hollow generic cavity showed good agreement with the computational data. This indicates that the electromagnetic susceptibility of an electronic sub-system with an enclosed metallic cavity can be readily exploited using the photonic-assisted system presented here. The strength and spectra of the resonant fields that passed through the aperture of the generic cavity at various internal locations are presented. This measurement system is quite effective at measuring actual fields without the need for a probe compensation procedure. Thus, it can be utilized for diagnosing the shielding of a generic system against intentional electromagnetic threats when the interiors of the generic objects become highly sophisticated.

Effect of phase noise on the generation of stationary entanglement in cavity optomechanics

We study the effect of laser phase noise on the generation of stationary entanglement between an intracavity optical mode and a mechanical resonator in a generic cavity optomechanical system. We show that one can realize robust stationary optomechanical entanglement even in the presence of non-negligible laser phase noise. We also show that the explicit form of the laser phase noise spectrum is relevant, and discuss its effect on both optomechanical entanglement and ground-state cooling of the mechanical resonator.

Laser phase noise effects on the dynamics of optomechanical resonators

We investigate theoretically the influence of laser phase noise on the cooling and heating of a generic cavity optomechanical system. We derive the back-action damping and heating rates and the mechanical frequency shift of the radiation-pressure-driven oscillating mirror, and derive the minimum phonon occupation number for small laser linewidths. We find that, in practice, laser phase noise does not pose serious limitations to ground-state cooling. Additionally, we explore the regime of parametric amplification where coherent oscillations of the mirror are realizable. It is found that heating from laser phase noise is of significance and can cause the onset of instabilities. We then consider the effects of laser phase noise in a parametric cavity driving scheme that minimizes the back-action heating of one of the quadratures of the mechanical oscillator motion. Laser linewidths, narrow compared to the decay rate of the cavity field, do not pose any significant problems in an experimental setting, but broader linewidths limit the practicality of this back-action evasion method.

Eigenmode changes in a misaligned triangular optical cavity

We derive relationships between various types of small misalignments in a triangularoptical cavity and associated geometrical eigenmode changes. We focus on the changes ofbeam spot positions on cavity mirrors, the beam waist position and its angle. A comparisonof analytical and numerical results shows excellent agreement. The results are applicable toany triangular cavity close to an isosceles triangle, with the lengths of two sides muchbigger than the third, consisting of a curved mirror and two flat mirrors (the curved mirroris the distant one) yielding a waist equally separated from the two flat mirrors. This cavityshape is most commonly used in laser interferometry. The analysis presented herecan easily be extended to more generic cavity shapes. The geometrical analysisnot only serves as a method of checking a simulation result, but also gives anintuitive and handy tool to visualize the eigenmode of a misaligned triangular cavity.

Bruit généré par un écoulement turbulent affleurant une cavité à faible nombre de Mach : application aux césures de portes automobiles

Noise produced by turbulent grazing flow over a generic cavity representing car door cavities was measured in a semi-anechoic wind tunnel. Two cavities were studied: one 50 mm large (dimension perpendicular to the airflow), functioning as a Helmholtz resonator, reaching sound pressure levels of 136 dB at 1776 Hz, for a downstream velocity of 54 m/s. The other, of scale 250 mm could not be regarded as a Helmholtz resonator although resonance occurred at 1902 Hz, at a level of 125 dB, for the same velocity. In both cases, noise was caused by Kelvin–Helmholtz instabilities in the mixing layer. To cite this article: A. Da Silva et al., C. R. Mecanique 337 (2009).

Investigations on ethylene combustion in a scramjet combustor using resistance heaters

In this article, the ignition characteristics of the gaseous ethylene hydrocarbon fuel is investigated in a supersonic clean airstream experimental facility with resistance heaters. A generic cavity flame holder is used to create a recirculation region and promote the fuel/air mixing at the lower wall of the combustor. Three different injection concepts are considered in this research: (a) ethylene injection upstream of the cavity; (b) ethylene and hydrogen injection upstream of the cavity simultaneously; and (c) ethylene injection preceded by pilot hydrogen injection. The pilot injection is a supportive tool for holding the flame of the main normal ethylene fuel injection. Therefore, using pilot hydrogen injection and cavity configuration necessitates optimizing the combustor length to ensure complete combustion and full liberation of the chemical energy stored in the fuel before exiting the combustor. This study proved the possibility of igniting the ethylene and maintaining its flame in the supersonic airstreams.

Modeling of ring resonators with tunable couplers

Controlling the characteristic response of the ring resonator through adjustable coupling can be useful in variety of applications, such as add-drop filters, modulators, lasers, switches, sensors and others. Coupled mode theory (CMT) is effectively utilized for modeling of a generic micro-resonant cavity with two independently adjustable add/drop couplers and integrated phase-shifter(s). It is shown that for a lossy cavity the non-identical input/output coupling values are required to satisfy a resonance condition. The critical coupling and coupling/loss optimization is discussed for the regular and /spl delta//spl beta/-reversal tunable couplers. Resonance coupling diagram is derived for passive and perturbed resonator structure for these types of tunable couplers.

Playing with podands based on cone-shaped cavities. How can a cavity influence the properties of an appended metal centre?

The potential of molecules that combine the properties of a conical cavity with those of a covalently-linked transition-metal centre is highlighted through the assessment of cyclodextrin- and calixarene-derived podands ("cavitand" ligands) in coordination chemistry and catalysis. Metallocavitands with coordination sites directed towards the interior of the generic cavity provide interesting systems for studying host-guest complexation processes, their enhanced strength of metal-ion binding allowing for regioselective catalysis in a confined environment, and stabilisation of coordination complexes of unusual forms. Where cavitands have exo-oriented podand arms, the intrinsic dynamics of the cavity can dramatically modify metal chelation behaviour and the catalytic properties of the complexes. Such functionalised cavities are also useful as metal-ion transporters.

Electromagnetic Excitation of a Generic Cavity with a Variable e-Beam Pulse

Relativistic electron-beam nose-erosion techniques have been employed to produce an electron beam with variable pulse shape and bremsstrahlung capability (dial a pulse). This capability has been employed to excite a large number of electromagnetic fields inside a canonical cavity. Electron-beam and bremsstrahlung pulse-shape parameters have been varied to produce changes in the electromagntic cavity response. For example, generic cavity test parameters such as displacement currents or conduction currents can be emphasized or de-emphasized. A theoretical interpretation of these electromagnetic excitations is presented.

Ionizing Radiation Dose Distribution Produced inside a Canonical Cavity by Direct e-Beam Excitation

Reliable dosimetry methods have been developed to map relativistic electrons that have been injected into a generic cavity. These measuring techniques are: (1) thermoluminescent dosimeters (TLDs) combined with photodiodes yielding dose rate; (2) TLD telescopes yielding electron angular distributions; and (3) TLD mosaic arrays yielding rough energy spectra. Total dose, dose rate, electron angular distribution and current density measurements have been obtained during electromagnetic excitation of a canonical cavity with diffuse electron beam (e-beam) bombardment. A theoretical interpretation of the dose rate and electron current density measurements is presented.