Dissipative Cavity Research Articles

Coherent population trapping for reservoir engineering and spin squeezing

Spin squeezing has important applications in the field of quantum metrology and quantum information processing. Here we propose that coherent population trapping is well suitable for establishing cavity dissipation mechanism and generating a spin-squeezed state. An ensemble of N double Λ-type atoms is placed inside the two-mode optical cavity, where one Λ subsystem is driven resonantly by two strong control fields to form a dark resonance and the other Λ subsystem is coupled by two cavity vacuum fields and two external fields with large detunings. Due to the dark resonance, the atoms are trapped in a dark state and one has the maximal coherence between the two ground states. Two double off-resonance stimulated Raman scattering interactions are induced between fields and dressed atoms to establish a dissipative quantum dynamical process based on a collective cavity reservoir. As a result, strong stable spin squeezing is generated, which is verified by our numerical and analytical results. Published by the American Physical Society 2024

A new experiment to enable rapid systematic investigations of flux trapping dynamics for superconducting radio-frequency cavity applications.

Many modern accelerators rely on superconducting radio-frequency (SRF) cavities to accelerate particles. When these cavities are cooled to the superconducting state, a fraction of the ambient magnetic field (e.g., Earth's magnetic field) may be trapped in the superconductor. This trapped flux can significantly increase the power dissipation of the SRF cavities. It is, therefore, crucial to understand the underlying mechanism of how magnetic flux is trapped and what treatments and operating conditions can reduce the flux-trapping efficiency. A new experiment was designed that enables a systemic investigation of flux trapping. It allows for independent control of cooldown conditions, which might have an influence on flux trapping: temperature gradient across the superconductor during cooldown, cooldown rate, and ambient magnetic field. For exhaustive studies, the setup was designed for quick thermal cycling, permitting up to 300 superconducting transitions in one day. In this paper, the setup and operation is described in detail and an estimation of the measurement errors is given. Exemplary data are presented to illustrate the efficacy of the system.

Coherent feedback ground state cooling of the mechanical resonator in quadratic optomechanical system assisted by an atomic ensemble

We propose a scheme for cooling a mechanical resonator to its ground state in a quadratic optomechanical system, assisted by an atomic ensemble in the unresolved sideband regime. The system features an auxiliary cavity directly coupled to an optical cavity, with a portion of the optical cavity’s output field being fed back through an asymmetric beam splitter. Utilizing quantum Langevin and master equations, we derive the optical fluctuation spectrum, the cooling rate, and the mean phonon number of the mechanical resonator. Our results demonstrate that the feedback mechanism substantially enhances the cooling rate. Furthermore, under optimal cooling conditions, the mechanical resonator achieves ground state cooling even with weaker optomechanical coupling strengths and higher auxiliary cavity dissipation rates, thereby mitigating the experimental constraints associated with these parameters. Additionally, we provide the feasible ranges for optomechanical coupling strength and atomic decay rates. Our findings suggest promising avenues for quantum manipulation in nonlinear systems and its applications in macroscopic optical devices.

Modulating entanglement dynamics of two V-type atoms in dissipative cavity by detuning and weak measurement reversal

It is studied how to modulate entanglement dynamics of two V-type atoms in dissipative cavity by detuning, weak measurement and weak measurement reversal. The analytical solution of this model is obtained by solving Schrödinger equation after diagonalizing Hamiltonian of dissipative cavity. It is discussed in detail how the entanglement dynamics is influenced by cavity-reservoir coupling, spontaneously generated interference (SGI) parameter, detuning between cavity with reservoir and weak measurement reversal. The results show that the entanglement dynamics of different initial states obviously depends on coupling, SGI parameter, detuning and reversing measurement strength. The stronger coupling, the smaller SGI parameter, the larger detuning and the bigger reversing measurement strength can all not only protect but also generate the entanglement, and the detuning is more effectively in the strong coupling regime than the weak measurement reversal, which is more effectively than the SGI parameter. We also provide the physical interpretations for these results.

Exploring optical tomography dynamics for a dissipative coherent cavity in interaction with two-level atomic system

In this paper, we explore the optical tomography and quantum coherence dynamics for a coherent cavity field interacting with a two-level atom via intensity dependent coupling. We derive a specific solution to the master equation for the Jaynes–Cummings model, considering cavity damping. This solution reveals how the atom coherent-cavity interactions can produce new coherent states when the initial dissipative cavity-field state is coherent state or even coherent state. The effects of the atom-coherent-cavity interactions and the cavity damping, on the dynamics of the initial coherent state optical tomography and coherence is examined. In addition to the nonclassical properties, the atom-cavity interactions have a remarkable capacity to form distinct cavity field states linked to certain optical tomography distributions. Additionally, we investigate the maximal optical tomography dynamics for coherent state and even coherent state considering a range of cavity damping and detuning values.

Effects of squeezed vacuum field on force sensing for a dissipative optomechanical system

We investigate the force sensing of a mechanical membrane in a dissipative cavity optomechanical system (OMS) driven by a squeezed vacuum field accompanying a strong pump laser. Specifically, the red-detuned laser exhibits a more significant improvement for force sensing compared to the blue-detuned laser. The optimal phase angle contributes to achieving much better force sensing. When injecting a squeezed vacuum field with appropriate squeezing parameter and squeezing phase, the standard quantum limit of force measurement can be easily beaten. Furthermore, the adverse effects of the increase in environment temperature and mechanical damping can be suppressed, simultaneously. This scheme provides a theoretical basics for force sensing of mechanical membranes in dissipative OMS and has potential applications in force feedback control, precision measurement, and force sensor design.

Reconciling quantum and classical spectral theories of ultrastrong coupling: role of cavity bath coupling and gauge corrections

Cavity quantum-electrodynamics (QED) is a rich area of optical physics, where extreme light–matter coupling can give rise to ultrastrong coupling. The ultrastrong coupling regime presents some fascinating uniquely quantum mechanical effects, such as ground state virtual photons and vacuum squeezing. Focusing on the widely adopted Hopfield model with cavity dissipation, we show how the linear spectrum of an ultrastrong coupled cavity and a dipole can be described either classically or quantum mechanically, but only when the quantum model includes (i) corrections to maintain gauge invariance, and (ii) a specific type of cavity bath coupling, which has so far not been identified. We also show the impact of this bath model on the quantum Rabi model, which has no classical analog in ultrastrong coupling. These results can be used to guide emerging experiments and significantly impact current models and interpretations of ultrastrong coupling between light and matter.

Unconventional photon blockade with non-Markovian effects in driven dissipative coupled cavities

Unconventional photon blockade with non-Markovian effects in driven dissipative coupled cavities

Dissipative and dispersive cavity optomechanics with a frequency-dependent mirror

An optomechanical microcavity can considerably enhance the interaction between light and mechanical motion by confining light to a subwavelength volume. However, this comes at the cost of an increased optical loss rate. Therefore, microcavity-based optomechanical systems are placed in the unresolved-sideband regime, preventing sideband-based ground-state cooling. A pathway to reduce optical loss in such systems is to engineer the cavity mirrors, i.e., the optical modes that interact with the mechanical resonator. In our work, we analyze such an optomechanical system, whereby one of the mirrors is strongly frequency dependent, i.e., a suspended Fano mirror. This optomechanical system consists of two optical modes that couple to the motion of the suspended Fano mirror. We formulate a quantum-coupled-mode description that includes both the standard dispersive optomechanical coupling as well as dissipative coupling. We solve the Langevin equations of the system dynamics in the linear regime showing that ground-state cooling from room temperature can be achieved even if the cavity is not in the resolved-sideband regime, but achieves effective sideband resolution through strong-optical-mode coupling. Importantly, we find that the cavity output spectrum needs to be properly analyzed with respect to the effective laser detuning to infer the phonon occupation of the mechanical resonator. Our work also predicts how to reach the regime of nonlinear quantum optomechanics in a Fano-based microcavity by engineering the properties of the Fano mirror. Published by the American Physical Society 2024

Dissipation-Induced Photon Blockade in the Anti-Jaynes–Cummings Model

Due to the fundamental differences between the quantum world and the classical world, some phenomena, such as entanglement and wave–particle duality, only exist in the quantum realm. These peculiar phenomena cannot be demonstrated by classical means: Quantum networks, quantum cryptography, and quantum precision measurements all require quantum sources. Photons are particularly well-suited as quantum sources owing to their minimal interaction with the environment, high flight speed, and ease of interaction with current typical quantum systems. Single-photon sources include pulsed excitation of quantum dots, spontaneous parametric down-conversion, and photon blockade. Herein, we propose that the anti-Jaynes–Cummings model can induce a pronounced photon antibunching effect when subjected to intense cavity dissipation. Similar to the photon blockade caused by strong photon–photon interaction, this antibunching effect is referred to as ’dissipation-induced blockade’. Our findings indicate that the minimum decay rate of a qubit, coupled with a high decay rate for photons, is conducive to achieving strong antibunching within the system. Notably, g(2)(0)<g(2)(τ), a characteristic of photon antibunching, is only valid under the optimal condition Δ=0. Conversely, g(2)(0)<1 is satisfied across all parameters, indicating that g(2)(0)<1 is not a prerequisite for antibunching in the anti-Jaynes–Cummings model. Moreover, under the optimal conditions of the antibunching effect, the average photon number attains its peak value. Consequently, the current anti-Jaynes–Cummings model is promising for developing single-photon sources characterized by excellent purity and average photon number.

Quantum Features of the Nonlinear Dissipative Cavity Interacting with a Two-Level Atom under the Influence of Stark Shift

Quantum Features of the Nonlinear Dissipative Cavity Interacting with a Two-Level Atom under the Influence of Stark Shift

Enhanced quantum resources via two distant atom-cavity systems under the influence of atomic dissipation

Quantum resources such as entanglement and coherence are the holy grail for modern quantum technologies. Although the unwanted environmental effects tackle quantum information processing tasks, suprisingly these key quantum resources may be protected and even enhanced by the implementation of some special hybrid open quantum systems. Here, we aim to show how a dissipative atom-cavity-system can be accomplished to generate enhanced quantum resources. To do so, we consider a couple of dissipative cavities, where each one contains two effective two-level atoms interacting with a single-mode cavity field. In practical applications, a classical laser field may be applied to drive each atomic subsystem. After driving the system, a Bell-state measurement is performed on the output of the system to quantify the entanglement and coherence. The obtained results reveal that the remote entanglement and coherence between the atoms existing inside the two distant cavities are not only enhanced, but can be stabilized, even under the action of dissipation. In contrast, the local entanglement between two atoms inside each dissipative cavity attenuates due to the presence of unwanted environmental effects. Nevertheless, the local coherence may show the same behavior as the remote coherence. Besides, the system provides the steady state entanglement in various interaction regimes, particularly in the strong atom-cavity coupling and with relatively large detuning. More interestingly, our numerical analyses demonstrate that the system may show a memory effect due to the fact that the death and revival of the entanglement take place during the interaction. Our proposed model may find potential applications for the implementation of long distance quantum networks. In particular, it facilitates the distribution of quantum resources between the nodes of large-scale quantum networks for secure communication.

Geometric Phase of a Transmon in a Dissipative Quantum Circuit.

Superconducting circuits reveal themselves as promising physical devices with multiple uses. Within those uses, the fundamental concept of the geometric phase accumulated by the state of a system shows up recurrently, as, for example, in the construction of geometric gates. Given this framework, we study the geometric phases acquired by a paradigmatic setup: a transmon coupled to a superconductor resonating cavity. We do so both for the case in which the evolution is unitary and when it is subjected to dissipative effects. These models offer a comprehensive quantum description of an anharmonic system interacting with a single mode of the electromagnetic field within a perfect or dissipative cavity, respectively. In the dissipative model, the non-unitary effects arise from dephasing, relaxation, and decay of the transmon coupled to its environment. Our approach enables a comparison of the geometric phases obtained in these models, leading to a thorough understanding of the corrections introduced by the presence of the environment.

Magnon-magnon entanglement generation between two remote interaction-free optomagnonic systems via optical Bell-state measurement

Finding new strategies for the generation and preservation of quantum resources, e.g. entanglement between spatially separated macroscopic systems enables reliable and fertile platforms to study both fundamental quantum physics and fruitful applications such as quantum networks and distant quantum information processing. Here, we want to address how to generate magnon-magnon entanglement (MME) in an optomagnonic system based on the optical Bell-state measurement. To do so, we consider a hybrid optomagnonic system comprising of two identical, but distant dissipative microwave cavities, each containing a ferromagnetic YIG sphere and a superconducting qubit. Besides, each subsystem is driven via an external laser field. We numerically simulate the solution of the corresponding master equation and discuss the time-dependent as well as the steady state entanglement between the distant magnon modes at different interaction regime. Also, the fidelity of the generated entangled states is studied in detail. Generally, the dissipative environmental effects plague the MME, however, it is possible to generate a considerable amount of MME even at the steady state regime. Also, the results show that the robust MME may be enhanced by applying a relatively strong external pump decreasing the relative magnon damping rate as well as increasing the relative qubit-photon coupling strength, while some other parameters involved in the model, i.e. the atomic damping rate and detuning parameter do not considerably affect the amplitude (the maximum value) of MME. Exceptionally, although the magnon damping rate decreases the amount of MME, the entanglement stability takes place in a longer time interval in the strong magnonic damping regime. Moreover, the maximum of the steady state entanglement may be obtained in the moderate magnon-photon coupling regime provided that the system is driven by strong external pumps. Furthermore, the system can generate robust MME at steady state, especially in the small detuning regime. Our further investigations show that the system can provide relatively high-fidelity magnonic entangled states even in the presence of inevitable environmental effects. The proposed model offers an attractive platform for the generation of quantum resources to establish long-distance quantum networks based on magnonic and photonic systems.

Cavity soliton formation in Kerr comb oscillators via input phase and amplitude modulation in the presence of high order dispersion

The generation of dissipative cavity solitons (CSs) in Kerr microresonators through pulsed driving is an effective method for generating coherent optical microcombs. Yet, the underlying physics has not been fully investigated. Our study investigates the effect of high-order dispersion on the generation of Kerr frequency combs in Si3N4 microresonator driven by phase- and amplitude-modulated inhomogeneities of the pump which had not been studied before. Here, we present a numerical and theoretical analysis of the effects of desynchronization and the pulsed driving chirp parameter on the train of solitons circulating in the cavity for various detunings. In this case, deterministic production of a K-band single soliton, as well single breather soliton has been investigated. Our results show that high-order dispersion can also affect CSs positioning, stability, and existence.

Distribution dynamics of fisher and Wigner–Yanase information correlations of two qubits coupled to an open superconducting cavity

In this paper, we explore distribution dynamics of two-qubit Fisher and skew information correlations of a dissipative microwave cavity field interacting with two charged superconducting qubits. Besides the negativity function, non-classical correlations beyond entanglement are studied using local quantum Fisher information (LQFI) and local quantum uncertainty (LQU). We find that the two-qubit non-classical correlations are sensitive to qubit–qubit distribution angle, two-qubit dissipation parameter, and initial coherent state intensity. The phenomena of frozen quantum correlations, sudden death or birth, as well as revival dynamical maps are feasible in the current two-qubit state when exposed to a microwave cavity. The non-classical correlations and entanglement have been found damped under the two-qubit dissipation appearance in the field. For the increasing strength of coherence intensity of the field, the two-qubit non-classical correlations functions remain to emerge quickly and oscillate with higher frequency, although with the least amplitudes. Interestingly, unlike the non-classical correlations, negativity does not emerge against higher coherence strengths of the cavity and remains completely zero. Finally, for the least dissipation and higher coherence strength, one can readily generate non-classical two-qubit states employing a microwave cavity.

Temperature mapping on a niobium-coated copper superconducting radio-frequency cavity

Since the late ’80s, CERN has pioneered the development of niobium thin film radio-frequency (RF) cavities deposited on copper substrates for several particle accelerator applications. However, niobium thin film cavities historically feature a progressive performance degradation as the accelerating field increases. In this study, we describe a temperature mapping system based on contact thermometry, specially designed to obtain temperature maps of niobium-coated copper cavities and, consequently, study the mechanisms responsible for performance degradation. The first temperature maps on a niobium/copper 1.3 GHz cavity are reported along with its RF performance. In addition to some hotspots displayed in the temperature maps, we surprisingly observed a temperature decrease in a limited portion of the cavity cell as the accelerating field increased. This may shed new light on understanding the heat dissipation of niobium thin film cavities in liquid helium-I, which might be exploited to improve the RF cavity performance.

Meterscale Strong Coupling between Magnons and Photons.

We experimentally realize a meterscale strong coupling effect between magnons and photons at room temperature, with a coherent coupling of ∼20 m and a dissipative coupling of ∼7.6 m. To this end, we integrate a saturable gain into a microwave cavity and then couple this active cavity to a magnon mode via a long coaxial cable. The gain compensates for the cavity dissipation, but preserves the cavity radiation that mediates the indirect photon-magnon coupling. It thus enables the long-range strong photon-magnon coupling. With full access to traveling waves, we demonstrate a remote control of photon-magnon coupling by modulating the phase and amplitude of traveling waves, rather than reconfiguring subsystems themselves. Our method for realizing long-range strong coupling in cavity magnonics provides a general idea for other physical systems. Our experimental achievements may promote the construction of information networks based on cavity magnonics.

Mechanical cooling in the bistable regime of a dissipative optomechanical cavity with a Kerr medium

Mechanical cooling in the bistable regime of a dissipative optomechanical cavity with a Kerr medium

Frequency–modulated qubits in a dissipative cavity: entanglement dynamics and protection

Frequency–modulated qubits in a dissipative cavity: entanglement dynamics and protection