Dissipative Cavity Research Articles

Single photon transport properties in coupled cavity arrays nonlocally coupled to a two-level atom in the presence of dissipation

We discuss the effects of dissipation on the behavior of single photon transport in a system of coupled cavity arrays, with the two nearest cavities nonlocally coupled to a two-level atom. The single photon transmission amplitude is solved exactly by employing the quasi-boson picture. We investigate two different situations of local and nonlocal couplings, respectively. Comparing the dissipative case with the nondissipative one reveals that the dissipation of the system increases the middle dip and lowers the peak of the single photon transmission amplitudes, broadening the line width of the transport spectrum. It should be noted that the influence of the cavity dissipation to the single photon transport spectrum is asymmetric. By comparing the nonlocal coupling with the local one, one can find that the enhancement of the middle dip of single photon transmission amplitudes is mostly caused by the atom dissipation and that the reduced peak is mainly caused by the cavity dissipation, no matter whether it is a nonlocal or local coupling case. Whereas in the nonlocal coupling case, when the coupling strength gets stronger, the cavity dissipation has a greater effect on the single photon transport spectrum and the atom dissipation affection becomes weak, so it can be ignored.

Dissipative Dynamics of Quantum Discord of Two Strongly Driven Qubits

The exact dynamics of quantum discord (QD) of two strongly driven qubits, which are initially prepared in the X-type quantum states and inserted in two independent dissipative cavities or in a common dissipative cavity, are studied. The results indicate that both in the two cases, the evolution of QD is independent of the initial cavity state. For the two independent dissipative cavities, it is found that the phenomenon of sudden transition between classical and quantum decoherence exists and the transition time can be greatly delayed by suitably choosing the initial state parameter of the two qubits, the cavity mode-driving field detunning and the decay rate of the cavity. For the common dissipative cavity, it is shown that for some initial states of the two qubits, the QD can increase for a finite time at first, and then it decreases to a steady value, while for some other initial states, the QD can increase monotonously or with oscillation till a stable value is reached. Moreover, the creation of QD for the two qubits in a common cavity is discussed.

A geometric phase for superconducting qubits under the decoherence effect

We propose a relaxation rate or dissipative cavity-based parameters that can be used as indicators of the stationary limit of a mixed state geometric phase. We perform our considerations for the system of a superconducting qubit in an open transmission line or interacting with a dissipative cavity. This system is very useful for performing an effective quantum computation by exhibiting the long collapse time of the geometric phase. It is shown that the geometric phase in the stationary limit does not depend on interaction time if the decay time exceeds an upper bound.

Generation of steady four-atom decoherence-free states via quantum-jump-based feedback

A scheme is presented for generating steady four-atom decoherence-free states via four atoms with the Raman level configuration interacting with a single-mode vacuum cavity field by using quantum-jump-based feedback. The scheme meets the condition of a strongly dissipative cavity easily and has a simplified feedback control. Although the spontaneous emission still plays a negative role in the proposed system, we can improve the feedback control to reduce its effect.

Three-qubit Grover’s algorithm using superconducting quantum interference devices in cavity-QED

We present a scheme for the implementation of three-qubit Grover’s algorithm using four-level superconducting quantum interference devices (SQUIDs) coupled to a superconducting resonator. The scheme is based on resonant, off-resonant interaction of the cavity field with SQUIDs and application of classical microwave pulses. We show that adjustment of SQUID level spacings during the gate operations, adiabatic passage, and second-order detuning are not required that leads to faster implementation. We also show that the marked state can be searched with high fidelity even in the presence of unwanted off-resonant interactions, level decay, and cavity dissipation.

Generation of macroscopic quantum superpositions of optomechanical oscillators by dissipation

We propose a scheme that exploits the combined effects of nonlinear dynamics and dissipation to generate macroscopic quantum superpositions in massive optomechanical oscillators. The effective degenerate three-wave mixing interaction between the mechanical and optical cavity modes that results from quadratic optomechanical coupling, together with the cavity dissipation, can result in the existence of dark macroscopic superpositions. We show analytically and confirm numerically that various quantum superpositions can be achieved deterministically, depending on the initial state of the mechanics. The effects of mechanical damping are also studied in detail and quantified by the negativity of the Wigner function. The present scheme can be realized in various optomechanical systems with current technology.

Control of sudden transition between classical and quantum correlations of two strongly driven atoms in dissipative cavities

We investigate analytically the dynamics of classical and quantum correlations between two strongly driven atoms, each of which is trapped inside a dissipative cavity. It is found that there exists a finite time interval during which the quantum discord initially prepared in the X-type states is not destroyed by the decay of the cavities. The sudden transition between classical correlation and quantum discord is sensitive to the initial-state parameter, the cavity decay rate, and the cavity mode-driving field detuning. Interestingly, we show that the transition time can be prolonged significantly by increasing the degree of the detuning.

The theory of single photon scattering by a three-level atom in a dissipative coupled cavity array

A microscopic model is developed in order to analyse the effects of dissipations on single-photon transport in a coupled cavity array where one of the cavities is coupled to a three-level atom and both cavities and the three-level atom are coupled to an external environment. By employing the quasi-boson approach, the single-photon transmission and reflection amplitudes are found exactly for the Ξ-type, V-type and Λ-type three-level atoms. We focus on the dissipation properties in the case of the Λ-type system. Comparing the dissipative case with the nodissipative one, it can be found that the dissipations of the cavities and the Λ-type three-level atom significantly affect the transmission amplitude of single-photon transport. Whether the atom is in tune with the resonant frequency of the cavity or not, incomplete reflection is mostly caused by atom dissipation near the middle dip of the single-photon transport spectrum, while reduced transmission appears to be mainly controlled by cavity dissipation. Dissipations broaden the line width of the single photon transport spectrum.

Quantum state transfer using stimulated Raman adiabatic passage under a dissipative environment

We propose a potentially practical scheme to realize arbitrary quantum state transfer between two traveling atoms that go through a high-finesse cavity by using stimulated Raman adiabatic passage in an atom-cavity-laser system under a dissipative environment. By numerically simulating the dynamics of the system, we demonstrate quantitatively that the fidelities of the quantum state transferred between two atoms can be maximized by elaborately adjusting the peak amplitudes of the laser's Rabi frequency and the detuning of the Raman transition. Additionally, the noise effect from the atomic and cavity dissipation can reduce the fidelity. The experimental feasibility is justified using currently available technology.

Two-photon transport through a waveguide coupling to a whispering-gallery resonator containing an atom and photon-blockade effect

We investigate the two-photon transport through a waveguide side-coupling to a whispering-gallery-atom system. Using the Lehmann-Symanzik-Zimmermann (LSZ) reduction approach, we present the general formula for the two-photon processes including the two-photon scattering matrices, the wavefunctions and the second order correlation functions of the out-going photons. Based on the exact results of the second order correlation functions, we analyze the quantum statistics behaviors of the out-going photons for two different cases: (a) the ideal case without the inter-modal coupling in the whispering gallery resonator; (b) the case in the presence of the inter-modal coupling which leads to more complex nonlinear behavior. In the ideal case, we show that the system consists of two independent scattering pathways, a free pathway by a cavity mode without atomic excitation, and a "Jaynes-Cummings" pathway described by the Jaynes-Cummings Hamiltonian of a single-mode cavity coupling to an atom. The free pathway does not contribution to correlated two-photon processes. In the presence of intermodal mixing, the system no longer exhibit a free resonant pathway. Instead, both the single-photon and the two photon transport properties depend on the position of the atom. Thus, in the presence of intermodal mixing one can in fact tune the photon correlation properties by changing the position of the atom. Our formalism can be used to treat resonator and cavity dissipation as well.

Collision-model-based approach to non-Markovian quantum dynamics

We present a theoretical framework to tackle quantum non-Markovian dynamics based on a microscopic collision model (CM), where the bath consists of a large collection of initially uncorrelated ancillas. Unlike standard memoryless CMs, we endow the bath with memory by introducing inter-ancillary collisions between next system-ancilla interactions. Our model interpolates between a fully Markovian dynamics and the continuous interaction of the system with a single ancilla, i.e., a strongly non-Markovian process. We show that in the continuos limit one can derive a general master equation, which while keeping such features is guaranteed to describe an unconditionally completely positive and trace-preserving dynamics. We apply our theory to an atom in a dissipative cavity for a Lorentzian spectral density of bath modes, a dynamics which can be exactly solved. The predicted evolution shows a significant improvement in approaching the exact solution with respect to two well-known memory-kernel master equations.

Dynamic dissipative cooling of a mechanical resonator in strong coupling optomechanics.

Cooling of mesoscopic mechanical resonators represents a primary concern in cavity optomechanics. In this Letter, in the strong optomechanical coupling regime, we propose to dynamically control the cavity dissipation, which is able to significantly accelerate the cooling process while strongly suppressing the heating noise. Furthermore, the dynamic control is capable of overcoming quantum backaction and reducing the cooling limit by several orders of magnitude. The dynamic dissipation control provides new insights for tailoring the optomechanical interaction and offers the prospect of exploring mesoscopic quantum physics.

Group delay of single-photon transmission in a waveguide side coupled with a Jaynes-Cummings chain

Using a real-space model Hamiltonian, we have theoretically studied the single-photon transmission in a waveguide side coupled with a Jaynes-Cummings chain (JCC). The JCC can induce the photon group advancement (GA) and group delay (GD) in different frequency ranges determined by JCC eigenmodes. For GA and GD, there exist different optimal JCC lengths. At certain frequency, the GA's maximum value as usual increases with decreasing the cavity dissipation, whereas the GD's eventually reaches saturation. For a 1.55 -μm photon, our calculation indicates that the GD's maximum value is about 400 ps simultaneously with a large transmission.

Dissipation-driven two-mode mechanical squeezed states in optomechanical systems

In this paper, we propose two quantum optomechanical arrangements that permit the dissipation-enabled generation of steady two-mode mechanical squeezed states. In the first setup, the mechanical oscillators are placed in a two-mode optical resonator while in the second setup the mechanical oscillators are located in two coupled single-mode cavities. We show analytically that for an appropriate choice of the pump parameters, the two mechanical oscillators can be driven by cavity dissipation into a stationary two-mode squeezed vacuum, provided that mechanical damping is negligible. The effect of thermal fluctuations is also investigated in detail and show that ground state pre-cooling of the oscillators in not necessary for the two-mode squeezing. These proposals can be realized in a number of optomechanical systems with current state-of-the-art experimental techniques.

Single-photon transport and mechanical NOON-state generation in microcavity optomechanics

We investigate the single-photon transport in a single-mode optical fiber coupled to an optomechanical system in the single-photon strong-coupling regime. The single-photon transmission amplitude is analytically obtained with a real-space approach and the effects of cavity and mechanical dissipations are studied via master-equation simulations. Based on the theoretical framework, we further propose a heralded probabilistic scheme to generate mechanical NOON states with arbitrary phonon numbers by measuring the sideband photons. The efficiency and fidelity of the scheme are discussed finally.

Achieving steady-state entanglement of remote micromechanical oscillators by cascaded cavity coupling

In this paper, we propose a scheme for generating steady-state entanglement of remote micromechanical oscillators in unidirectionally-coupled cavities. For the system of two mechanical oscillators, we show that when two cavity modes in each cavity are driven at red- and blue-detuned sidebands, respectively, a stationary two-mode squeezed vacuum state of the two mechanical oscillators can be generated with the help of the cavity dissipation. The degree of squeezing is controllable by adjusting the relative strength of the pump lasers. Our calculations also show that the achieved mechanical entanglement is robust against thermal fluctuations of phononic environments. For the case of multiple mechanical oscillators, we find that the steady-state genuine multipartite entanglement can also be built up among the remote mechanical oscillators by the cavity dissipation. The present scheme does not require nonclassical light input or conditional quantum measurements, and it can be realized with current experimental technology.

Sudden transition and sudden change of quantum discord in dissipative cavity quantum electrodynamics system

The dynamics of classical correlation and quantum correlation of two qubits in an independent and common dissipative cavity are studied. We show that for an independent case, the quantum correlation keeps constant and the correlation relation decays before the critical time point Ωt¯. On the other hand t>Ωt¯, for the classical correlation does not change and the quantum correlation is lost. These situations demonstrate that the phenomenon of sudden transition between classical and quantum decoherence appears during the time evolution. For the common case, the quantum correlation dynamics is quite different. It is displayed that for some initial states, the quantum correlation can increase up to the critical point of time, after which it decreases, which means that the quantum correlation presents a sudden change of behavior in their decay rates. But for other initial states, the quantum correlation can keep increasing up to some-steady state value. Furthermore, we also investigate the nonzero quantum correlation between two qubits induced by the dissipation of the cavity.

Tripartite entanglement dynamics in a system of strongly driven qubits

We study the dynamics of tripartite entanglement in a system of two strongly driven qubits individually coupled to a dissipative cavity. We aim to explain the previously noted entanglement revival between two qubits in this system. We show that the periods of entanglement loss correspond to the tripartite entanglement formation between the qubits and the cavity, and the recovery is associated with an inverse process. We demonstrate that the overall process of qubit–qubit entanglement loss is due to the coupling to the cavity, and further loss of multipartite entanglement is due to the coupling of the cavity to the external continuum, which explains the behaviour of the qubit–qubit entanglement loss reported previously.

Climbing the Jaynes–Cummings ladder by photon counting

A scheme to observe direct experimental evidence of Jaynes-Cummings nonlinearities in a strongly dissipative cavity quantum electrodynamics system was devised. In such a system, large losses compete with the strong light-matter interaction. Comparing coherent and incoherent excitations of the system, it was shown that resonant excitation of the detuned emitter makes it possible to evidence few photon quantum nonlinearities in currently available experimental systems.

The evolution and stability of quantum correlations in dissipative cavity

We investigate the dynamics of quantum correlations such as entanglement and quantum discord between two atoms in a lossy cavity. It is found that a stable quantum discord could be induced even when the atoms remain separable at all times. Also, we show that it is possible to amplify and protect the quantum discord under cavity decay for certain types of initial states. Moreover, entanglement decoherence-free subspaces are obtained which may be useful in quantum information and quantum computation.