0000000000199146
AUTHOR
Myungshik Kim
Resilience of singlet-state extraction against non-optimal resonance conditions
We have recently presented a protocol for extracting the singlet state of two non-interacting high-dimensional spins through post-selection of the internal state of interaction mediators sent in succession [F. Ciccarello et al., arXiv:0710.3855v1]. The scheme requires each mediator's wavevector to obey appropriate resonance conditions. Here we show the robustness of the scheme in the realistic case where such conditions are not sharply fulfilled.
Nonequilibrium dressing in a cavity with a movable reflecting mirror
We consider a movable mirror coupled to a one-dimensional massless scalar field in a cavity. Both the field and the mirror's mechanical degrees of freedom are described quantum-mechanically, and they can interact each other via the radiation pressure operator. We investigate the dynamical evolution of mirror and field starting from a nonequilibrium initial state, and their local interaction which brings the system to a stationary configuration for long times. This allows us to study the time-dependent dressing process of the movable mirror interacting with the field, and its dynamics leading to a local equilibrium dressed configuration. Also, in order to explore the effect of the radiation …
Journeys from quantum optics to quantum technology
Sir Peter Knight is a pioneer in quantum optics which has now grown to an important branch of modern physics to study the foundations and applications of quantum physics. He is leading an effort to develop new technologies from quantum mechanics. In this collection of essays, we recall the time we were working with him as a postdoc or a PhD student and look at how the time with him has influenced our research.
Accumulation of entanglement in a continuous variable memory
We study the accumulation of entanglement in a memory device built out of two continuous variable (CV) systems. We address the case of a qubit mediating an indirect joint interaction between the CV systems. We show that, in striking contrast with respect to registers built out of bidimensional Hilbert spaces, entanglement superior to a single ebit can be efficiently accumulated in the memory, even though no entangled resource is used. We study the protocol in an immediately implementable setup, assessing the effects of the main imperfections.
Entanglement between two superconducting qubits via interaction with nonclassical radiation
We propose a scheme to physically interface superconducting nano-circuits and quantum optics. We address the transfer of quantum information between systems having different physical natures and defined in Hilbert spaces of different dimensions. In particular, we investigate the transfer of the entanglement initially in a non-classical state of a continuous-variable system to a pair of superconducting charge qubits. This set-up is able to drive an initially separable state of the qubits into an almost pure, highly entangled state suitable for quantum information processing.
Extraction of Singlet States from Noninteracting High-Dimensional Spins
We present a scheme for the extraction of singlet states of two remote particles of arbitrary quantum spin number. The goal is achieved through post-selection of the state of interaction mediators sent in succession. A small number of iterations is sufficient to make the scheme effective. We propose two suitable experimental setups where the protocol can be implemented.
Non-Markovianity of a quantum emitter in front of a mirror
We consider a quantum emitter ("atom") radiating in a one-dimensional (1D) photonic waveguide in the presence of a single mirror, resulting in a delay differential equation for the atomic amplitude. We carry out a systematic analysis of the non-Markovian (NM) character of the atomic dynamics in terms of refined, recently developed notions of quantum non-Markovianity such as indivisibility and information back-flow. NM effects are quantified as a function of the round-trip time and phase shift associated with the atom-mirror optical path. We find, in particular, that unless an atom-photon bound state is formed a finite time delay is always required in order for NM effects to be exhibited. Th…
Quantum state transfer in imperfect artificial spin networks
High-fidelity quantum computation and quantum state transfer are possible in short spin chains. We exploit a system based on a dispersive qubit-boson interaction to mimic XY coupling. In this model, the usually assumed nearest-neighbors coupling is no more valid: all the qubits are mutually coupled. We analyze the performances of our model for quantum state transfer showing how pre-engineered coupling rates allow for nearly optimal state transfer. We address a setup of superconducting qubits coupled to a microstrip cavity in which our analysis may be applied.
Dynamics of spontaneous emission in a single-end photonic waveguide
We investigate the spontaneous emission of a two-level system, e.g. an atom or atomlike object, coupled to a single-end, i.e., semi-infinite, one-dimensional photonic waveguide such that one end behaves as a perfect mirror while light can pass through the opposite end with no back-reflection. Through a quantum microscopic model we show that such geometry can cause non-exponential and long-lived atomic decay. Under suitable conditions, a bound atom-photon stationary state appears in the atom-mirror interspace so as to trap a considerable amount of initial atomic excitation. Yet, this can be released by applying an atomic frequency shift causing a revival of photon emission. The resilience of…