Electromagnetic Cavity Mode Research Articles

Universal and Ultrafast Quantum Computation Based on Free-Electron-Polariton Blockade

Cavity QED, wherein a quantum emitter is coupled to electromagnetic cavity modes, is a powerful platform for implementing quantum sensors, memories, and networks. However, due to the fundamental trade-off between gate fidelity and execution time, as well as limited scalability, the use of cavity QED for quantum computation was overtaken by other architectures. Here, we introduce a new element into cavity QED—a free charged particle, acting as a flying qubit. Using free electrons as a specific example, we demonstrate that our approach enables ultrafast, deterministic, and universal discrete-variable quantum computation in a cavity-QED-based architecture, with potentially improved scalability. Our proposal hinges on a novel excitation blockade mechanism in a resonant interaction between a free-electron and a cavity polariton. This nonlinear interaction is faster by several orders of magnitude with respect to current photon-based cavity-QED gates, enjoys wide tunability and can demonstrate fidelities close to unity. Furthermore, our scheme is ubiquitous to any cavity nonlinearity, either due to light-matter coupling as in the Jaynes-Cummings model or due to photon-photon interactions as in a Kerr-type many-body system. In addition to promising advancements in cavity-QED quantum computation, our approach paves the way towards ultrafast and deterministic generation of highly entangled photonic graph states and is applicable to other quantum technologies involving cavity QED. Published by the American Physical Society 2024

Resonant Polariton Thermal Transport Along a Vacuum Gap

Going with the flow: The authors show that, in contrast to the well-known cross-plane heat transport in a cavity, the in-plane transport increases with gap distance up to 1 cm, where it takes on a maximum value that increases with temperature. This resonance occurs due to the thermal activation of hundreds of electromagnetic cavity modes, which are standing waves in the cross-plane direction, yet propagate within the plane. The energy of these modes leads to thermal emission comparable to the radiation predicted by Planck's law, and this effect could be useful for generating and evacuating super-Planckian heat currents along macroscale cavities.

Charge-transfer chemical reactions in nanofluidic Fabry-Pérot cavities

We investigate the chemical reactivity of molecular populations confined inside a nanofluidic Fabry-P\'erot cavity. Due to strong light-matter interactions developing between a resonant electromagnetic cavity mode and the electric dipole moment of the confined molecules, a collective polariton excitation is formed. The former gets dressed by environmental vibrational and rotational degrees of freedom of the solvent. We call the resulting polariton dressed by its cloud of environmental excitation a ``reacton'', since it further undergoes chemical reactions. We characterize how the reacton formation modifies the kinetics of a photoisomerization chemical reaction involving an elementary charge-transfer process. We show that the reaction driving force and reorganization energy are both modulated optically by the reactant concentration, the vacuum Rabi splitting, and the detuning between the Fabry-P\'erot cavity frequency and targeted electronic transition. Finally, we compute the ultrafast picosecond dynamics of the whole photochemical reaction. We predict that despite optical cavity losses and solvent-mediated nonradiative relaxation, measurable signatures of the reacton formation can be found in state-of-the-art pump-probe experiments.

Deterministic generation of hybrid high- N NOON states with Rydberg atoms trapped in microwave cavities

Trapped ions are among the most promising platforms for quantum technologies. They are at the heart of the most precise clocks and sensors developed to date, which exploit the quantum coherence of a single electronic or motional degree of freedom of an ion. However, future high precision quantum metrology will require the use of entangled states of several degrees of freedom. Here we propose a protocol capable of generating high N00N states where the entanglement is shared between the motion of a trapped ion and an electromagnetic cavity mode, a so called hybrid configuration. We prove the feasibility of the proposal in a platform consisting of a trapped ion excited to its circular Rydberg state manifold, coupled to the modes of a high Q microwave cavity. This compact hybrid architecture has the advantage that it can couple to signals of very different nature, which modify either the ions motion or the cavity modes. Moreover, the exact same setup can be used right after the state preparation phase to implement the interferometer required for quantum metrology.

Study of the combined effects of a Kerr nonlinearity and a two-level atom upon a single nonstationary cavity mode

We study a simple version of the dynamical Casimir effect in a single electromagnetic cavity mode containing a Kerr medium and a two-level atom. We obtain approximate expressions for the time-evolution operator valid at short times and/or low average photon number. We have found an interplay between the effect of the nonlinear Kerr medium, which is to decrease the growth of photon generation from the vacuum state, and that of the two-level atom, which is to increase the photon generation. We explore an ample range of Hamiltonian parameters going from the resonant to the dispersive regimes.

Organic polaritons enable local vibrations to drive long-range energy transfer

Long-range energy transfer in organic molecules has been experimentally obtained by strongly coupling their electronic excitations to a confined electromagnetic cavity mode. Here, we shed light into the polariton-mediated mechanism behind this process for different configurations: donor and acceptor molecules either intermixed or physically separated. We numerically address the phenomenon by means of Bloch-Redfield theory, which allows us to reproduce the effect of complex vibrational reservoirs characteristic of organic molecules. Our findings reveal the key role played by the middle polariton as the non-local intermediary in the transmission of excitations from donor to acceptor molecules. We also provide analytical insight on the key physical magnitudes that helps to optimize the efficiency of the long-range energy transfer.

A comparative study on the reliability of non-Hermitian effective Hamiltonian approach for modeling open quantum systems

In this paper, we conduct a comprehensive analysis on the reliability of non-Hermitian effective Hamiltonian approach for modeling quantum dissipative dynamics. It is found that one of the major drawbacks to adopting this theoretical approach is that it fails to reproduce correctly both the dynamics and the time evolution of observables of the system. With this in mind, we propose a method that allows correcting the non-Hermitian effective Hamiltonian approach when there exists a conserved quantity in the system. In order to illustrate the performance of our corrected non-Hermitian effective Hamiltonian approach, we consider a two-level system interacting with an electromagnetic cavity mode where the effects of the environment are included in a phenomenological manner. More precisely, the dissipation and pump in the system are considered through non-Hermitian Hamiltonian terms. Our numerical results have been focused on the time evolution of density matrix elements, observables as well as the emission spectrum of the system, and they demonstrate that our proposed methodology is in excellent agreement with the predictions of the Lindblad master equation approach.

Terahertz emission from the intrinsic Josephson junctions of high-symmetry thermally-managed Bi2Sr2CaCu2O8+δ microstrip antennas

We show for high-symmetry disk, square, or equilateral triangular thin microstrip antennas of any composition respectively obeying C∞v, C4v, and C3v point group symmetries, that the transverse magnetic electromagnetic cavity mode wave functions are restricted in form to those that are one-dimensional representations of those point groups. Plots of the common nodal points of the ten lowest-energy non-radiating two-dimensional representations of each of these three symmetries are presented. For comparison with symmetry-broken disk intrinsic Josephson junction microstrip antennas constructed from the highly anisotropic layered superconductor Bi2Sr2CaCu2O8+δ (BSCCO), we present plots of the ten lowest frequency orthonormal wave functions and of their emission power angular distributions. These results are compared with previous results for square and equilateral triangular thin microstrip antennas.

Terahertz Emission From Thermally Managed Square Intrinsic Josephson Junction Microstrip Antennas

We show for thin square microstrip antennas that the transverse magnetic electromagnetic cavity modes are greatly restricted in number due to the point group symmetry of a square. For the ten lowest frequency emissions, we present plots of the orthonormal wave functions and of the angular distributions of the emission power obtained from the uniform Josephson current source and from the excitation of an electromagnetic cavity mode excited in the intrinsic Josephson junctions between the layers of a highly anisotropic layered superconductor.

Cavity mode enhancement of terahertz emission from equilateral triangular microstrip antennas of the high-Tc superconductor Bi2Sr2CaCu2O8 + δ

We study the transverse magnetic (TM) electromagnetic cavity mode wave functions for an ideal equilateral triangular microstrip antenna (MSA) exhibiting C3v point group symmetry. When the C3v operations are imposed upon the antenna, the TM(m,n) modes with wave vectors are much less dense than commonly thought. The R3 operations restrict the integral n and m to satisfy , where and for the modes even and odd under reflections about the three mirror planes, respectively. We calculate the forms of representative wave functions and the angular dependence of the output power when these modes are excited by the uniform and non-uniform ac Josephson current sources in thin, ideally equilateral triangular MSAs employing the intrinsic Josephson junctions in the high transition temperature Tc superconductor Bi2Sr2CaCu2, and fit the emissions data from an earlier sample for which the C3v symmetry was apparently broken.

Emission of Circularly Polarized Terahertz Wave From Inhomogeneous Intrinsic Josephson Junctions

We have theoretically demonstrated the emission of circularly-polarized terahertz (THz) waves from intrinsic Josephson junctions (IJJs) which is locally heated by an external heat source such as the laser irradiation. We focus on a mesa-structured IJJ whose geometry is slightly deviate from a square and find that the local heating make it possible to emit circularly-polarized THz waves. In this mesa, the inhomogeneity of critical current density induced by the local heating excites the electromagnetic cavity modes TM (1,0) and TM (0,1), whose polarizations are orthogonal to each other. The mixture of these modes results in the generation of circularly-polarized THz waves. We also show that the circular polarization dramatically changes with the applied voltage. The emitter based on IJJs can emit circularly-polarized and continuum THz waves by the local heating, and will be useful for various technological application.

Making hybrid quantum information systems

Quantum Information Different physical implementations of qubits—quantum bits—each have their pros and cons. An appealing idea is to combine them into hybrid architectures, taking advantage of their respective strengths. Tabuchi et al. placed a ferromagnetic sphere and a superconducting qubit in a cavity and used an electromagnetic mode of the cavity as the mediator between the two. They achieved strong coupling between a collective magnetic mode of the sphere and the qubit. Viennot et al. coupled a single spin in a double quantum dot to photons in a cavity. Both approaches hold promise for future applications. Science , this issue pp. [405][1] and [408][2] [1]: /lookup/doi/10.1126/science.aaa3693 [2]: /lookup/doi/10.1126/science.aaa3786

Modes and Mode Volumes of Leaky Optical Cavities and Plasmonic Nanoresonators

Electromagnetic cavity modes in photonic and plasmonic resonators offer rich and attractive regimes for tailoring the properties of light-matter interactions. Yet there is a disturbing lack of a precise definition for what constitutes a cavity mode, and as a result their mathematical properties remain largely unspecified. The lack of a definition is evidenced in part by the diverse nomenclature at use - "resonance", "leaky mode", "quasimode", to name but a few - suggesting that the dissipative nature of cavity modes somehow makes them different from other modes, but an explicit distinction is rarely made. This perspective article aims to introduce the reader to some of the subtleties and working definitions that can be rigorously applied when describing the modal properties of leaky optical cavities and plasmonic nanoresonators. We describe some recent development in the field, including {calculation methods for quasinormal modes of both photonic and plasmonic resonators and the concept of a generalized effective mode volume, and we} illustrate the theory with several representative cavity structures from the fields of photonic crystals and nanoplasmonics.

Spin bath maser in a cryogenically cooled sapphire whispering gallery mode resonator

We report the observation of a mechanism of maser generation in an ensemble of inter-coupled, inhomogeneously broadened two-level systems, enhanced by high quality factor electromagnetic cavity modes. In this previously unobserved form of population inversion, an inseparable quantum system leads to cavity-enhanced stimulated emission arising from interactions within an ensemble of two-level systems, as opposed to a traditional ensemble of noninteracting identical three level systems. The effect is observed in a cryogenically cooled whispering gallery mode sapphire resonator containing dilute Fe$^{3+}$ impurity ions. These ions exhibit strong spin-lattice interaction, leading to both electron spin resonance broadening and phonon mediated spin-spin coupling. The maser effect is due to a $\left|1/2\right\rangle \rightarrow \left|3/2\right\rangle$ energy transition in electron spin angular momentum observed at zero external magnetic field. Both continuous and oscillating regimes are observed with corresponding thresholds both in detuning frequency and incident power.

Terahertz Oscillating Devices Based Upon the Intrinsic Josephson Junctions in a High Temperature Superconductor

Recent developments of coherent terahertz (THz) oscillators based on the intrinsic Josephson junctions (IJJs) in mesas of the high temperature superconductor Bi2Sr2CaCu2O8+δ are reviewed. Experimental and theoretical studies of the emission from equilateral, right-angled isosceles, and acute isosceles triangular mesas are compared with those obtained from rectangular, square, and disk mesas, in order to determine the role of the mesa geometry. The superconducting properties and emission frequency f spectra are presented for a variety of triangular mesa geometries. Analytic and finite difference time domain numerical calculations of the emissions from the internal electromagnetic (EM) cavity modes of triangular mesas are compared with experiment. The experimental f always satisfies the ac Josephson relation, and its narrow linewidth arises from the synchronized emissions from many IJJs. For some mesa geometries, f also strongly locks onto an EM cavity mode frequency, enhancing the emission’s stability and output power. For other geometries, such cavity mode locking is weak, and f is highly tunable.

Effect of dielectric constant tuning on a photonic cavity frequency and Q-factor

For practical applications in quantum electrodynamics, it has been proposed to produce frequency tuning or Q-switching by dynamically changing the dielectric constant around a nano-cavity. Local changes in the dielectric constant of a photonic cavity with finite-lifetime, may affect not only the frequency of electromagnetic cavity modes but also their quality-factor (Q). Thus, it is important to have prediction capability regarding the combined effect of these changes. Here perturbation theory, usually applied to eigenmodes with real eigenvalues, is formulated in the complex domain, in which the eigen-frequency imaginary part is related to the Q-factor. Normalizable leaky modes, and bi-orthogonality in a finite volume are the basis for such a formulation. We introduce such capabilities by presenting semi-analytical expressions of first order perturbation analysis for a 3D cavity with radiation losses. The obtained results are in good agreement with numerical calculations.

Quantum quenches in the Dicke model: Statistics of the work done and of other observables

We study the statistics of the work done in a zero temperature quench of the coupling constant in the Dicke model describing the interaction between an ensemble of two level systems and a single bosonic mode. When either the final or the initial coupling constants approach the critical coupling lambdac that separates the normal and superradiant phases of the system, the probability distribution of the work done displays singular behavior. The average work tends to diverge as the initial coupling parameter is brought closer to the critical value lambdac. In contrast, for quenches ending close to criticality, the distribution of work has finite moments but displays a sequence of edge singularities. This contrasting behavior is related to the difference between the processes of compression and expansion of a particle subject to a sudden change in its confining potential. We confirm this by studying in detail the time-dependent statistics of other observables, such as the quadratures of the photons and the total occupation of the bosonic modes.

Cavity formation in split ring resonators

We report that it is possible to obtain a cavity structure by the deformation of a unit cell of an split ring resonator (SRR) structure. We presented the Q-factor of the cavity resonance as 192 for an SRR-based single cavity. Subsequently, we brought two and three cavities together with an intercavity distance of two metamaterial unit cells and investigated the transmission spectrum of SRR-based interacting 2-cavity and 3-cavity systems. The splitting of eigenmodes due to the interaction between the localized electromagnetic cavity modes was observed. Eventually, in taking full advantage of the effective medium theory, we modeled SRR-based cavities as 1D Fabry–Perot reflectors (FPRs) with a subwavelength cavity at the center. Finally, we observed that at the cavity resonance, the effective group velocity was reduced by a factor of 67 for an SRR-based single cavity compared to the electromagnetic waves propagating in free space.

Observation of coupled-cavity structures in metamaterials

In this letter, we investigated the transmission properties of metamaterial based coupled-cavity structures. We first calculated the effective parameters of a split-ring resonator (SRR) and composite metamaterial (CMM) structures. Subsequently, we introduced coupled-cavity structures and presented the transmission spectrum of SRR and CMM based coupled-cavity structures. The splitting of eigenmodes was observed due to the interaction between the localized electromagnetic cavity modes. Finally, the dispersion relation and normalized group velocity of the coupled-cavity structures were calculated. The maximum group velocity was found to be 100 times smaller than the speed of light in vacuum.

Efficiency of frequency-pulsed excitation of a micron-sized spherical microcavity by chirped ultrashort laser radiation

Peculiarities of internal optical field resonant excitation inside micron-sized spherical transparent dielectric cavity illuminated by a train of ultrashort laser pulses are investigated. On an example of water microdroplet is shown that optimal tuning of incident radiation to a selected high-Q resonance electromagnetic cavity mode can be realized by varying temporal interpulse interval in a laser train together with linear frequency modulation of every pulse (chirp). Efficiency of resonant particle excitation by a chirped picosecond pulses train can be considerably increased as compared to unchirped pulse train and CW excitation also.