Protecting quantum resources via frequency modulation of qubits in leaky cavities (original) (raw)
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Quantum technology relies on the utilization of resources, like quantum coherence and entanglement, which allow quantum information and computation processing. This achievement is however jeopardized by the detrimental effects of the environment surrounding any quantum system, so that finding strategies to protect quantum resources is essential. Non-Markovian and structured environments are useful tools to this aim. Here we show how a simple environmental architecture made of two coupled lossy cavities enables a switch between Markovian and non-Markovian regimes for the dynamics of a qubit embedded in one of the cavity. Furthermore, qubit coherence can be indefinitely preserved if the cavity without qubit is perfect. We then focus on entanglement control of two independent qubits locally subject to such an engineered environment and discuss its feasibility in the framework of circuit quantum electrodynamics. With up-to-date experimental parameters, we show that our architecture allo...
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Non-Markovian features of a system evolution, stemming from memory effects, may be utilized to transfer, storage, and revive basic quantum properties of the system states. It is well known that an atom qubit undergoes non-Markovian dynamics in high quality cavities. Here we consider the qubit-cavity interaction in the case when the qubit is in motion inside a leaky cavity. We show that, owing to the inhibition of the decay rate, the coherence of the travelling qubit remains closer to its initial value as time goes by compared to that of a qubit at rest. We also demonstrate that quantum coherence is preserved more efficiently for larger qubit velocities. This is true independently of the evolution being Markovian or non-Markovian, albeit the latter condition is more effective at a given value of velocity. We however find that the degree of non-Markovianity is eventually weakened as the qubit velocity increases, despite a better coherence maintenance.
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The quantum information carried by a two-level atom was transferred to a high-Q cavity and, after a delay, to another atom. We realized in this way a quantum memory made of a field in a superposition of 0 and 1 photon Fock states. We measured the "holding time" of this memory corresponding to the decay of the field intensity or amplitude at the single photon level. This experiment implements a step essential for quantum information processing operations. [S0031-9007(97)03701-0] PACS numbers: 89.70. + c, 03.65. -w, 32.80. -t, 42.50. -p The manipulation of simple quantum systems interacting in a well-controlled environment is a very active field in quantum optics, with strong connections to the theory of quantum information . Atoms and photons can be viewed as carriers of "quantum bits" (or qubits) storing and processing information in a nonclassical way. The interaction between two qubit carriers can model the operation of a quantum gate in which the evolution of one qubit is conditioned by the state of the other [2,3]. Combining a few qubits and gates could lead to the realization of simple quantum networks in which an "engineered entanglement" between the interacting qubits carriers could be achieved. Even if practical applications to large scale quantum computing are likely to remain inaccessible [4], fundamental tests of quantum theory could be performed, such as demonstrations of new quantum nonlocal effects , decoherence studies, etc.
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The position-dependent entanglement dynamics of two qubits embedded in a leakage cavity is investigated. The two qubits are initialled in Bell states and the cavity mode is taken as a standing wave. It is found that (i) the dynamics of the Bell states can be divided into two groups according to one-photon entangled states and two-photon entangled states; (ii) the entanglement life of the one-photon entangled states can be kept as long as possible if we put the two qubits at certain positions; (iii) at larger detuning, the entanglement dynamics manifests more robustly.
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