Perfect and flexible quantum state transfer in the hybrid system atom coupled-cavity (original) (raw)
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The European Physical Journal D, 2011
We propose a scheme for deterministic generation of entanglement embodied by two Λ-type atoms distributed in two coupled cavities. We study such a system in the dispersive atom-field interactions, where the dynamics of the system operates through the virtual population of both the atomic excited states and the photonic states in the cavities (plus the fiber). We verify the validity of the dynamics, and moreover, study the influences of the decoherence due to the spontaneous emission and photon leakage. We also apply the dynamics for realizing quantum state transfer and quantum phase gates.
Quantum-state transmission in a cavity array via two-photon exchange
Physical Review A, 2012
The dynamical behavior of a coupled cavity array is investigated when each cavity contains a three-level atom. For the uniform and staggered intercavity hopping, the whole system Hamiltonian can be analytically diagonalized in the subspace of single-atom excitation. The quantum-state transfer along the cavities is analyzed in detail for distinct regimes of parameters, and some interesting phenomena including binary transmission and selective localization of the excitation population are revealed. We demonstrate that the uniform coupling is more suitable for the quantum-state transfer. It is shown that the initial state of polariton located in the first cavity is crucial to the transmission fidelity, and the local entanglement depresses the state transfer probability. Exploiting the metastable state, the distance of the quantum-state transfer can be much longer than that of Jaynes-Cummings-Hubbard model. A higher transmission probability and longer distance can be achieved by employing a class of initial encodings and final decodings.
Atoms versus photons as carriers of quantum states
Physical Review A, 2013
The problem of the complete transfer of quantum states and entanglement in a four-qubit system composed of two single-mode cavities and two two-level atoms is investigated. The transfer of single and double excitation states is discussed for two different coupling configurations between the qubits. In the first, the coupling is mediated by the atoms that simultaneously couple to the cavity modes. In the second configuration, each atom resides inside one of the cavities and the coupling between the cavities is mediated by the overlapping field modes. A proper choice of basis states makes it possible to identify states that could be completely transferred between themselves. Simple expressions are derived for the conditions for the complete transfer of quantum states and entanglement. These conditions impose severe constraints on the evolution of the system in the form of constants of motion. The constrains on the evolution of the system imply that not all states can evolve in time, and we find that the evolution of the entire system can be confined into that occurring among two states only. Detailed analysis show that in the case where the interaction is mediated by the atoms, only symmetric superposition states can be completely and reversibly transferred between the atoms and the cavity modes. In the case where the interaction is mediated by the overlapping field modes, both symmetric and antisymmetric superposition states can be completely transferred. We also show that the system is capable of generating purely photonic NOON states, but only if the coupling is mediated by the atoms, and demonstrate that the ability to generate the NOON states relies on perfect transfer of an entanglement from the atoms to the cavity modes.
Information Transfer in Leaky Atom–Cavity Systems
International Journal of Quantum Information, 2006
We consider a system of two enatangled cavities and a single two-level atom passing through one of them. A "monogamy" inequality for this tripartite system is quantitatively studied and verified in the presence of cavity leakage. Next, we consider the simultaneous passage of two-level atoms through both the cavities. Entanglement swapping is observed between the the two-cavity and the two-atom system. Cavity dissipation leads to the quantitative reduction of information transfer though preserving the basic swapping property.
Single photon transfer controlled by excitation phase in a two-atom cavity system
Journal of Physics B: Atomic, Molecular and Optical Physics
We investigate the quantum interference effects of single photon transfer in two-atom cavity system caused by external excitation phase. In the proposed system, two identical atoms (with different positions in the optical cavity) are firstly prepared into a timed state by an external single photon field. During the excitation, the atoms grasp different phases which depend on the spatial positions of the atoms in the cavity. Due to strong resonant interaction between two atoms and optical cavity mode the absorbed input photon can be efficiently transferred from the atoms to the resonant cavity mode. We show that the quantum transfer is highly sensitive to the external excitation phases of atoms and it leads to quantum interference effects on the cavity mode excitation. Besides, the quantum transfer is also influenced by the dipole-dipole interaction dependent to the atomic distance. In this system the atomic positions also determine the coupling constants between atoms and cavity mode which causes additional interference effects to the photon exchange between atoms and cavity. Based on the characteristics of excitation phase we find that it is a feasible scheme to generate long-lived dark state and it could be useful for storage and manipulation of single photon fields by controlling the excitation phase.
Atom-field entanglement in a bimodal cavity
2021
We investigate some aspects of the dynamics and entanglement of bipartite quantum system (atom-quantized field), coupled to a third “external” subsystem (quantized field). We make use of the Raman coupled model; a three-level atom in a lambda configuration interacting with two modes of the quantized cavity field. We consider the far off resonance limit, which allows the derivation of an effective Hamiltonian of a two-level atom coupled to the fields. We also make a comparison with the situation in which one of the modes is treated classically rather than prepared in a quantum field (coherent state).
Dynamics of atom-field entanglement in a bimodal cavity
The European Physical Journal D, 2011
We investigate some aspects of the dynamics and entanglement of bipartite quantum system (atom-quantized field), coupled to a third "external" subsystem (quantized field). We make use of the Raman coupled model; a three-level atom in a lambda configuration interacting with two modes of the quantized cavity field. We consider the far off resonance limit, which allows the derivation of an effective Hamiltonian of a two-level atom coupled to the fields. We also make a comparison with the situation in which one of the modes is treated classically rather than prepared in a quantum field (coherent state).
Entanglement between artificial atoms and photons of lossless cavities
Journal of Physics: Conference Series
We investigated the dynamics of atom-field entanglement for two natural or artificial two-level atoms interacting with a one-mode quantum electromagnetic field by means of multiphoton transitions in a lossless cavity. Tavis-Cummings model is used to describe the interaction of the atoms and real microwave coplanar cavity field. We carried out the mathematical modeling of the dynamics of the system under consideration for various initial states of the atomic subsystem and an intensive coherent field of the cavity. We showed that for small multiplicities, the atoms and the field, which were initially in a pure separable state, can return to this state during the evolution. We also found that for large multiplicities the atoms and the field are in the entangled atom-field state in the process of the system evolution with the exception of the initial time instant. These results can be used in the theory of quantum networks.
Strong interaction between light and a single trapped atom without a cavity
Many quantum information processing protocols require efficient transfer of quantum information from a flying photon to a stationary quantum system. To transfer information, a photon must first be absorbed by the quantum system. A flying photon can be absorbed by an atom residing in a high-finesse cavity with a probability close to unity. However, it is unclear whether a photon can be absorbed effectively by an atom in a free space. Here, we report on an observation of substantial extinction of a light beam by a single 87 Rb atom through focusing light to a small spot with a single lens. The measured extinction values are not influenced by interference-related effects, and thus can be compared directly to the predictions by existing free-space photon-atom coupling models. Our result opens a new perspective on processing quantum information carried by light using atoms, and is important for experiments that require strong absorption of single photons by an atom in free space.
Nature Communications
In a cavity quantum electrodynamics (QED) system, where atoms coherently interact with photons in a cavity, the eigenstates of the system are the superposition states of atoms and cavity photons, the so-called dressed states of atoms. When two cavities are connected by an optical fiber with negligible loss, the coherent coupling between the cavities gives rise to photonic normal modes. One of these normal modes is the fiber-dark mode, in which photons are delocalized in the two distant cavities. Here we demonstrate the setting of coupledcavities QED, where two nanofiber cavity-QED systems are coherently connected by a meterlong low-loss channel in an all-fiber fashion. Specifically, we observe dressed states of distant atoms with delocalized photons of the fiber-dark normal mode. Our system will provide a platform for the study of delocalized atomic and photonic states, photonic many-body physics, and distributed quantum computation.