Leaky Cavity Research Articles

Damped Casimir radiation and photon correlation measurements

An effective toy model for an ideal one-dimensional nonstationary cavity is taken to be the starting point to derive a fitting markovian master equation for the corresponding leaky cavity. In the regime where the generation of photons via the dynamical Casimir effect is bounded, the master equation thus constructed allows us to investigate the effects of decoherence on the average number of Casimir photons and their quantum fluctuations through the second-order correlation function.

Computational passive imaging of thermal sources with a leaky chaotic cavity

Computational imaging techniques are of great interest to simplify the architecture of imaging devices since random illuminations of a scene enable its reconstruction from few measurements by solving an inverse problem. Here, we present a passive system for imaging of thermal sources in the microwave range from the cross-correlation of noise signals recorded by only two channels. The channels are attached to a high Q-factor chaotic cavity with a leaky aperture on its front side. The spatial distribution of noise sources is encoded onto the broadband spectrum of the cross-correlation and can be reconstructed from the sensing matrix mapping the uncorrelated far-field speckle patterns of the cavity onto a set of frequencies. We demonstrate imaging of localized and extended thermal sources and show that the polarization of those radiations can be discriminated. Moreover, we exhibit the effectiveness of the proposed system as a compressive imaging device which exploits the natural randomness of the speckle patterns. We believe that these results are a promising step for the design of real time and low cost microwave radiometers.

Computational polarimetric microwave imaging

We propose a polarimetric microwave imaging technique that exploits recent advances in computational imaging. We utilize a frequency-diverse cavity-backed metasurface, allowing us to demonstrate high-resolution polarimetric imaging using a single transceiver and frequency sweep over the operational microwave bandwidth. The frequency-diverse metasurface imager greatly simplifies the system architecture compared with active arrays and other conventional microwave imaging approaches. We further develop the theoretical framework for computational polarimetric imaging and validate the approach experimentally using a multi-modal leaky cavity. The scalar approximation for the interaction between the radiated waves and the target- often applied in microwave computational imaging schemes-is thus extended to retrieve the susceptibility tensors, and hence provides additional information about the targets. Computational polarimetry has relevance for existing systems in the field that extract polarimetric imagery, and particular for ground observation. A growing number of short-range microwave imaging applications can also notably benefit from computational polarimetry, particularly for imaging objects that are difficult to reconstruct when assuming scalar estimations.

Non-Markovianity and Coherence of a Moving Qubit inside a Leaky Cavity

Non-Markovian features of a system evolution, stemming from memory effects, may be utilized to transfer, storage, and revive basic quantum properties of the system states. It is well known that an atom qubit undergoes non-Markovian dynamics in high quality cavities. Here we consider the qubit-cavity interaction in the case when the qubit is in motion inside a leaky cavity. We show that, owing to the inhibition of the decay rate, the coherence of the travelling qubit remains closer to its initial value as time goes by compared to that of a qubit at rest. We also demonstrate that quantum coherence is preserved more efficiently for larger qubit velocities. This is true independently of the evolution being Markovian or non-Markovian, albeit the latter condition is more effective at a given value of velocity. We however find that the degree of non-Markovianity is eventually weakened as the qubit velocity increases, despite a better coherence maintenance.

A compact time reversal emitter-receiver based on a leaky random cavity

Time reversal acoustics (TRA) has gained widespread applications for communication and measurements. In general, a scattering medium in combination with multiple transducers is needed to achieve a sufficiently large acoustical aperture. In this paper, we report an implementation for a cost-effective and compact time reversal emitter-receiver driven by a single piezoelectric element. It is based on a leaky cavity with random 3-dimensional printed surfaces. The random surfaces greatly increase the spatio-temporal focusing quality as compared to flat surfaces and allow the focus of an acoustic beam to be steered over an angle of 41°. We also demonstrate its potential use as a scanner by embedding a receiver to detect an object from its backscatter without moving the TRA emitter.

Origin and implications of anA2-like contribution in the quantization of circuit-QED systems

By placing an atom into a cavity, the electromagnetic mode structure of the cavity is modified. In Cavity QED, one manifestation of this phenomenon is the appearance of a gauge-dependent diamagnetic term, known as the $A^2$ contribution. Although in atomic Cavity QED, the resulting modification in the eigenmodes is negligible, in recent superconducting circuit realizations, such corrections can be observable and may have qualitative implications. We revisit the canonical quantization procedure of a circuit QED system consisting of a single superconducting transmon qubit coupled to a multimode superconducting microwave resonator. A complete derivation of the quantum Hamiltonian of an open circuit QED system consisting of a transmon qubit coupled to a leaky transmission line cavity is presented. We introduce a complete set of modes that properly conserves the current in the entire structure and present a sum rule for the dipole transition matrix elements of a multi-level transmon qubit coupled to a multi-mode cavity. Finally, an effective multi-mode Rabi model is derived with coefficients that are given in terms of circuit parameters.

Protection of Quantum Correlation Through the Quantum Erasing Effect

By taking into account the quantum erasing effect(QEE), the quantum discord (QD) behavior of a two-qubit system with different initial states are investigated in detail. We find that the quantum correlation can be saved under a scheme of two spatially separated atoms, each located in a leaky cavity through the quantum erasing method. It is shown that QEE can weaken the effects of decoherence, and preserve the maximum information of the coherent item. No matter whether the two atoms are in the mixted or pure state, one can robusty save their initial quantum correlation even the number of erasing events is finite. If one limit the erasing events N → ∞, the QEE can be used to protect the initial quantum correlation independently of the state in which it is stored, the values of QD is always nearly equal to the initial QD values, and it is nearly independent of the decoherence, which imply us more encourage strategy for protecting the quantum correlation properties in some quantum systems.

Quantum Discord Dynamics of Three Qubits in Non-Markovian Environments

We investigate the dynamics of pairwise quantum discord (QD) for a mixed three-qubit W-type state in three independent non-Markovian reservoirs at zero temperature, each of which is modeled by a leaky cavity with Lorentzian spectral density. The influence of the environment's amount of non-Markovianity, the detuning between the qubit frequency and the cavity centre frequency, and the purity of the initial state on the QD dynamics are analyzed in detail. It is found that in the non-Markovian regime the system-reservoir interactions induce QD revivals and oscillations no matter whether the detuning is zero or not. Moreover, QD can be preserved for a long time if the non-Markovian condition and the detuning condition are satisfied simultaneously.

Dissipative dynamics of atom–field entanglement in the ultrastrong-coupling regime

The dynamics of atom–field entanglement for a system composed of two atoms resonantly coupled to a single mode leaky cavity field has been investigated beyond rotating wave approximation (RWA). By using a monogamic relation for the entanglement of formation (EOF) as well as the lower bound of the EOF for bipartite mixed states in higher dimensions, contrary to the RWA case, the atom–field system in the steady states is found to be entangled in the strong-coupling regime and the entanglement can grow as a function of atom–field coupling strength.

Silicon-on-Glass Graphene-Functionalized Leaky Cavity Mode Nanophotonic Biosensor

Subwavelength silicon nanostructures are known to support highly localized resonant optical modes. These resonances are spectrally narrow with an electromagnetic near-field that extends significantly into the surrounding medium. Here, we demonstrate that leaky cavity mode resonances (LCMR) in periodic silicon nanowire arrays can serve as a platform for low-cost, label-free, and highly sensitive biosensing and establish a theoretical framework for the LCMR phenomenon that is consistent with experimental results. The sensors exhibit bulk refractive index sensitivities up to 213 nm/RIU. Moreover, by functionalizing the surface of silicon nanostructures with a graphene monolayer, such structures can be used to optically detect low-concentration surface adsorption events. The specific label-free detection limit using immunoglobulin G protein (IgG) is found to be on the order of 300 pM with an extracted maximum sensor resonance shift of 5.42 nm. This sensing platform holds significant promise for unraveling pro...

Formulation for scalable optimization of microcavities via the frequency-averaged local density of states

We present a technique for large-scale optimization of optical microcavities based on the frequency-averaged local density of states (LDOS), which circumvents computational difficulties posed by previous eigenproblem-based formulations and allows us to perform full topology optimization of three-dimensional (3d) leaky cavity modes. We present theoretical results for both 2d and fully 3d computations in which every pixel of the design pattern is a degree of freedom ("topology optimization"), e.g. for lithographic patterning of dielectric slabs in 3d. More importantly, we argue that such optimization techniques can be applied to design cavities for which (unlike silicon-slab single-mode cavities) hand designs are difficult or unavailable, and in particular we design minimal-volume multi-mode cavities (e.g. for nonlinear frequency-conversion applications).

Spatial modulation of above-the-gap cathodoluminescence in InP nanowires

We report the observation of light emission on wurtzite InP nanowires excited by fast electrons. The experiments were performed in a scanning transmission electron microscope using an in-house-built cathodoluminescence detector. Besides the exciton emission, at 850 nm, emission above the band gap from 400 to 800 nm was observed. In particular, this broad emission presented systematic periodic modulations indicating variations in the local excitation probability. The physical origin of the detected emission is not clear. Measurements of the spatial variation of the above-the-gap emission points to the formation of leaky cavity modes of a plasmonic nature along the nanowire length, indicating the wave nature of the excitation. We propose a phenomenological model, which fits closely the observed spatial variations.

Elastic and viscous effects on flow pattern of elasto-viscoplastic fluids in a cavity

Inertialess flows of elasto-viscoplastic fluids inside a leaky cavity are numerically analyzed using the finite element technique, with the goal of understanding the influence of both the elastic and viscous effects on the topology of the yield surfaces of an elasto-viscoplastic material. Assuming that the collapse of the material microstructure is instantaneous, a mechanical model is composed of the governing equations of mass and momentum for incompressible fluids, and associated with a hyperbolic equation for the extra-stress tensor based on the Oldroyd-B model (Nassar et al., 2011). The main feature of the model is the consideration of the viscosity and relaxation time as functions of the strain rate to allow the shear-thinning of the viscosity and to restrict the elastic effects to the unyielded regions of the material. The numerical simulations are performed through a three-field Galerkin least-squares-type method in terms of the extra-stress tensor and the pressure and velocity fields. The results indicate that the material yield surfaces are strongly influenced by the interplay between the elastic and viscous effects, in accordance with recent experimental visualization of elasto-viscoplastic flows.

Dissipative dynamics of quantum correlations in the strong-coupling regime

The dynamics of entanglement and quantum discord between two identical qubits strongly interacting with a common single mode leaky cavity field have been investigated beyond the rotating wave approximation (RWA) by using recently derived Lindblad type quantum optical master equation [F. Beaudoin, J.M. Gambetta, A. Blais, Phys. Rev. A {\bf 84}, 043832 (2011)] that can describe the losses of the cavity field in a strong atom-field coupling regime. Contrary to previous investigations of the same model in the dissipative regime by using the standard Lindblad quantum optical master equation in a strong-coupling regime, the atom-field steady states are found to be cavity decay rate independent and have a very simple structure determined solely by the overlap of initial atomic state with the subradiant state which is valid for all coupling regimes. Non-RWA dynamics are found to have remarkable effects on the steady state quantum discord and entanglement that cannot be achieved under RWA conditions, for instance, they can induce steady state entanglement even for the initial states that have no overlap with the subradiant state. Moreover, the non-RWA dynamics are found to reverse the initial state dependence of steady state entanglement and quantum discord contrary to the RWA case.

Lamb shift of a lossy two-level emitter inside a leaky cavity: A universal description based on an equivalent dissipative model

We present an universal description for Lamb shift of a lossy two-level-emitter (TLE) inside a leaky cavity by combining the quantum dissipation theory and the perturbative treatment developed in cavity QED. The total spectrum function of bath associated with the TLE is deduced by the standard method developed for a quantum dissipation model, from which the total spontaneous emission rate and Lamb shift are calculated. The developed calculation scheme is able to reproduce the known Purcell enhancement factor and is shown to be in agreement with the analysis made for a confocal resonator. It is found that the Lamb shift due to a leaky cavity mode has a sharp drop when sweeping across the resonance point. The physics behind this unusual behavior and the related experimental observations made on both atom-cavity and quantum-dot cavity systems are also analyzed.

基于单边傅里叶变换的非马尔科夫自发辐射研究

Based on one-sided Fourier transformation,a general method is presented to research the spontaneous decay dynamics of an emitter in homogeneous media,non-leaky cavity,leaky cavity and photonic band gap material.It is found that the spontaneous decay properties of the emitters are strongly dependent on the local density of states.The spontaneous emission properties of the emitters can be manipulated through engineering the local density of stats and the high-performance optoelectronic device and quantum information processing device are obtained.This method can be used in Markovian or non-Markovian bath-reservoir environments.

Non-Markovianity and Clauser-Horne-Shimony-Holt (CHSH)-Bell inequality violation in quantum dissipative systems

We examine the non-Markovian dynamics in a multipartite system of two initially correlated atomic qubits, each located in a single-mode leaky cavity and interacting with its own bosonic reservoir. We show the dominance of non-Markovian features, as quantified by the difference in fidelity of the evolved system with its density matrix at an earlier time, in three specific two-qubit partitions associated with the cavity-cavity and atom-reservoir density matrices within the same subsystem, and the cavity-reservoir reduced matrix across the two subsystems. The non-Markovianity in the cavity-cavity subsystem is seen to be optimized in the vicinity of the exceptional point. The Clauser-Horne-Shimony-Holt (CHSH)-Bell inequality computed for various two-qubit partitions show that high non-locality present in a specific subsystem appears in conjunction with enhanced non-Markovian dynamics in adjacent subsystems. This is in contrast to the matching existence of non-locality and quantum correlations in regions spanned by time t and the cavity decay rate, λ(c) for select partitions. We discuss the applicability of these results to photosynthetic systems.

Protection of Two-Qubit Entanglement by the Quantum Erasing Effect

We present a scheme to save the entanglement of two spatially separated atoms, each located in a leaky cavity, through the quantum erasing method. It is shown that no matter whether the two atoms are in the pure or mixed state, one can robustly save their initial entanglement even if the number of erasing events is finite. We also briefly discuss the challenging aspect of implementing such a scheme.

Satellite observations of Schumann resonances in the Earth's ionosphere

[1] Using electric field measurements gathered on the C/NOFS satellite, we report, Schumann resonance signatures detected in space, well beyond the upper boundary of the resonant cavity formed by the earth's surface and the lower edge of the ionosphere. The resonances are routinely observed in the satellite ELF data during nighttime conditions within the altitude region of 400–850 km sampled by the satellite. They exhibit the distinctive frequency patterns predicted for Schumann resonances and are consistent with the corresponding frequency characteristics of ground-based observations of this phenomenon. The observations of Schumann resonances in space support a leaky cavity interpretation of the ionosphere and call for revisions of models of extremely low frequency wave propagation in the ionosphere. They suggest new remote sensing capabilities for investigating atmospheric electricity on Earth and other planets.

DYNAMICS AND EXTRACTION OF QUANTUM DISCORD IN A MULTIPARTITE OPEN SYSTEM

We consider a multipartite system consisting of two noninteracting qubits each embedded in a single-mode leaky cavity, in turn connected to an external bosonic reservoir. Initially, we take the two qubits in an entangled state while the cavities and the reservoirs have zero photons. We investigate, in this six-partite quantum system, the transfer of quantum discord from the qubits to the cavities and reservoirs. We show that this transfer also occurs when the cavities are not entangled. Moreover, we discuss how quantum discord can be extracted from the cavities and transferred to distant systems by traveling leaking photons, using the input–output theory.