Preprints

    31 a 45 de 67 Preprints encontradas

  • GIQ-UFABC
    GOIQ - UFRJ
    Inducing nontrivial qubit coherence through a controlled dispersive environment
    Wallace S. Teixeira, Fernando Nicacio, Fernando L. Semião
    Phys. Rev. A 99 (2019)
    ArXiv: https://arxiv.org/abs/1807.11502
    Abstract

    We show how the dispersive regime of the Jaynes-Cummings model may serve as a valuable tool to the study of open quantum systems. We employ it in a bottom-up approach to build an environment that preserves qubit energy and induces varied coherence dynamics. We then present the derivation of a compact expression for the qubit coherence, applied here to the case of a finite number of thermally populated modes in the environment. We also discuss how the model parameters can be adjusted to facilitate the production of short-time monotonic decay (STMD) of the qubit coherence. Our results provide a broadly applicable platform for the investigation of energy-conserving open system dynamics which is fully within the grasp of current quantum technologies.

  • A definition of Quantum Mechanical Work
    Thales A. B. Pinto Silva
    (2019)
    ArXiv: https://arxiv.org/abs/1904.07438
  • Concentration phenomena in the geometry of Bell correlations
    Cristhiano Duarte, Samuraí Brito, Barbara Amaral, Rafael Chaves
    (2018)
    ArXiv: https://arxiv.org/abs/1810.00443
  • Machine learning non-local correlations
    Askery Canabarro, Samuraí Brito, Rafael Chaves
    (2018)
    ArXiv: https://arxiv.org/abs/1808.07069
  • GTQS - UFPR
    Nonanomalous measure of realism-based nonlocality
    V. S. Gomes, R. M. Angelo
    Phys. Rev. A 97 (2018)
    ArXiv: https://arxiv.org/abs/1709.04783
  • GOQIQ - UFMG
    GMCT - UFRJ
    LabNS - UFMG
    GOIQ - UFRJ
    Energy, momentum and production rate of photonic Cooper pairs
    Filomeno S. de Aguiar Junior, Andre Saraiva, Marcelo F. Santos, Belita Koiller, Reinaldo de Melo e Souza, Arthur Patrocinio Pena, Raigna A. Silva, Carlos H. Monken, Ado Jorio
    (2018)
    ArXiv: https://arxiv.org/abs/1810.12461
  • GOIQ - UFRJ
    GOQIQ - UFMG
    Steady State Entanglement beyond Thermal Limits
    F. Tacchino, A. Auffèves, M. F. Santos, D. Gerace
    Phys. Rev. Lett. 120, 063604 (2018)
    ArXiv: https://arxiv.org/abs/1710.01377
    Abstract

    Classical engines turn thermal resources into work, which is maximized for reversible operations. The quantum realm has expanded the range of useful operations beyond energy conversion, and incoherent resources beyond thermal reservoirs. This is the case of entanglement generation in a driven-dissipative protocol, which we hereby analyze as a continuous quantum machine. We show that for such machines the more irreversible the process, the larger the concurrence. Maximal concurrence and entropy production are reached for the hot reservoir being at negative effective temperature, beating the limits set by classic thermal operations on an equivalent system.

  • GTQS - UFPR
    Information-reality complementarity: The role of measurements and quantum reference frames
    P. R. Dieguez, R. M. Angelo
    Phys. Rev. A 97 (2018)
    ArXiv: https://arxiv.org/abs/1711.07739
  • GTQS - UFPR
    Unitary equivalence between the Green's function and Schrödinger approaches for quantum graphs
    Fabiano M. Andrade, Simone Severini
    Phys. Rev. A 98 (2018)
    ArXiv: https://arxiv.org/abs/1808.01154
  • GCQIQ - CBPF
    Quantum walks via quantum cellular automata
    Pedro C. S. Costa, Renato Portugal, Fernando de Melo
    Quantum Inf Process 17, 226 (2018)
    ArXiv: https://arxiv.org/abs/1803.02176
    Abstract

    Very much as its classical counterpart, quantum cellular automata are expected to be a great tool for simulating complex quantum systems. Here we introduce a partitioned model of quantum cellular automata and show how it can simulate, with the same amount of resources (in terms of effective Hilbert space dimension), various models of quantum walks. All the algorithms developed within quantum walk models are thus directly inherited by the quantum cellular automata. The latter, however, has its structure based on local interactions between qubits, and as such it can be more suitable for present (and future) experimental implementations.

  • GTQS - UFPR
    Weak quantum discord
    P. R. Dieguez, R. M. Angelo
    Quantum Inf Process 17 (2018)
    ArXiv: https://arxiv.org/abs/1804.04983
  • GOIQ - UFRJ
    Relative phase shifts for metaplectic isotopies acting on mixed Gaussian states
    Maurice A. de Gosson, Fernando Nicacio
    Journal of Mathematical Physics 59 (2018)
    ArXiv: https://arxiv.org/abs/1802.07499
    Abstract

    We address in this paper the notion of relative phase shift for mixed quantum systems. We study the Pancharatnam-Sjoeqvist phase shift for metaplectic isotopies acting on Gaussian mixed states. We complete and generalize previous results obtained by one of us while giving rigorous proofs. This gives us the opportunity to review and complement the theory of the Conley-Zehnder index which plays an essential role in the determination of phase shifts.

  • GTQS - UFPR
    Resilience of realism-based nonlocality to local disturbance
    V. S. Gomes and R. M. Angelo
    (2018)
    ArXiv: https://arxiv.org/abs/1805.01859
  • QIEP - UFSM
    Gradient target propagation
    Tiago de Souza Farias, Jonas Maziero
    (2018)
    ArXiv: https://arxiv.org/abs/1810.09284
  • GIQ-UFABC
    GCQIQ - CBPF
    Experimental characterization of a spin quantum heat engine
    John P. S. Peterson, Tiago B. Batalhão, Marcela Herrera, Alexandre M. Souza, Roberto S. Sarthour, Ivan S. Oliveira, Roberto M. Serra
    arXiv:1803.06021 (2018)
    ArXiv: https://arxiv.org/abs/1803.06021
    Abstract

    Developments in the thermodynamics of small quantum systems envisage non-classical thermal machines. In this scenario, energy fluctuations play a relevant role in the description of irreversibility. We experimentally implement a quantum heat engine based on a spin-1/2 system and nuclear magnetic resonance techniques. Irreversibility at microscope scale is fully characterized by the assessment of energy fluctuations associated with the work and heat flows. We also investigate the efficiency lag related to the entropy production at finite time. The implemented heat engine operates in a regime where both thermal and quantum fluctuations (associated with transitions among the instantaneous energy eigenstates) are relevant to its description. Performing a quantum Otto cycle at maximum power, the proof-of-concept quantum heat engine is able to reach an efficiency for work extraction (η≈42%) very close to its thermodynamic limit (η=44%).

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