We study optomechanical entanglement between an optical cavity field and a movable mirror coupled to a non-Markovian environment. The non-Markovian quantum state diffusion (NMQSD) approach and the non-Markovian master equation are shown to be useful in investigating the entanglement generation between the cavity field and the movable mirror. The simple model presented in this paper demonstrates several interesting properties of optomechanical entanglement that are associated with environment memory effects. It is evident that the effective environment central frequency can be used to modulate the optomechanical entanglement. In addition, we show that the maximum entanglement may be achieved by properly choosing the effective detuning which is significantly dependent on the strength of the memory effect of the environment.
We consider a three-level cascade laser with a self-phase-locked type-II nondegenerate optical parameter oscillator via a homodyne-mediate quantum feedback. Applying the pertinent master equation, we investigate the squeezing, entanglement properties and the mean photon number produced by our system. It is found that highly squeezed and macroscopic entangled light with high intensity can be generated.
In this paper, we present a scheme to generate an entangled coherent state by considering a threelevel "Λ" type atom interacting with a two-mode cavity driven by classical fields. The two-mode entangled coherent state can be obtained under large detuning condition. Considering the cavity decay, an analytical solution is deduced.
We consider an open quantum system consisting of four atoms which are placed in a damped cavity. Through a dissipative dynamics process, a W state can be converted into a Greenberger-Horne-Zeilinger state with deterministic probability. In addition, the interaction time need not be controlled strictly in the dynamics process.The protocol may open up a promising perspective for quantum state conversion between different classes of entanglement and cavity quantum electrodynamics systems.It is well known that quantum entanglement plays an important role because of its extensive application in quantum information processing. Thus generation of entanglement in hybrid quantum information systems [1-3] has become an active research field. Meanwhile, the task of classifying multiqubit entanglement beyond two qubits becomes difficult. In particular, Dür et al. [4] have shown that there exist two inequivalent kinds of entanglement: the Greenberger-Horne-Zeilinger (GHZ) state and the W state, which cannot be converted to each other by local operations and classical communication. Two kinds of entangled states can perform different tasks of quantum information theory [5]. Naturally, the question of how the two kinds of entanglement can be converted into each other arises. Inspired by entanglement concentration, the authors [6] propose a scheme for converting a GHZ state into an approximate W state based on partial quantum measurement and experimentally apply the scheme in the three-qubit case. In Ref.[7], two EPR photon pairs are transformed into a three-photon W state after the photons pass a linear-optical circuit. These works shed new light on the way to implement the conversion of quantum states.Atoms are regarded as a kind of useful information qubit because they are suited to store the information in stationary nodes. However, the coupling of a quantum system with its surrounding environment is unavoidable, which destroys the coherence of the system [8]. Overcoming the decoherence is still a formidable physical challenge both in experiments and in theory. Recent investigations show that atomic spontaneous emission [9] or photonic decay [10] can be exploited to generate an entangled state in a cavity. Furthermore, entanglement distillation [11] and quantum computation [12] might be implemented by controlling dissipation. The achievements mentioned above have ignited great interest in realizing noiseassisted quantum information processing [13,14]. Is it possible to convert a W state into a GHZ state via engineering decay? In this paper, we explore the possibility of converting a four-qubit W state into a four-qubit GHZ state in a dissipative cavity. Once the cavity decay drives the transition from the W state t the GHZ * jsong@hit.edu.cn † xia-208@163.com state, it remains there with a high fidelity. The operation time need not be controlled accurately. In addition, the influence of atomic spontaneous emission is suppressed by choosing a large frequency detuning.We consider that four identical multilevel atoms interact w...
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