Now showing items 21-40 of 13534

    • Shortcuts to adiabaticity from linear response theory 

      Acconcia, Thiago V.; Bonança, Marcus V. S.; Deffner, Sebastian (American Physical Society (APS), 2015-10-23)
      A shortcut to adiabaticity is a finite-time process that produces the same final state as would result from infinitely slow driving. We show that such shortcuts can be found for weak perturbations from linear response ...
    • Non-hermitian quantum thermodynamics 

      Gardas, Bartłomiej; Deffner, Sebastian; Saxena, Avadh (Springer Nature, 2016-03-22)
      Thermodynamics is the phenomenological theory of heat and work. Here we analyze to what extent quantum thermodynamic relations are immune to the underlying mathematical formulation of quantum mechanics. As a main result, ...
    • Optimal driving of isothermal processes close to equilibrium 

      Bonança, Marcus V. S.; Deffner, Sebastian (AIP publishing, 2014-06-30)
      We investigate how to minimize the work dissipated during nonequilibrium processes. To this end, we employ methods from linear response theory to describe slowly varying processes, i.e., processes operating within the ...
    • Quantum work and the thermodynamic cost of quantum measurements 

      Deffner, Sebastian; Paz, Juan Pablo; Zurek, Wojciech H. (American Physical Society (APS), 2016-07-07)
      Quantum work is usually determined from two projective measurements of the energy at the beginning and at the end of a thermodynamic process. However, this paradigm cannot be considered thermodynamically consistent as it ...
    • Optimal control of a qubit in an optical cavity 

      Deffner, Sebastian (IOP, 2014-07-04)
      We study quantum information processing by means of optimal control theory. To this end, we analyze the damped Jaynes–Cummings model, and derive optimal control protocols that minimize the heating or energy dispersion ...
    • Jarzynski Equality in PT-Symmetric Quantum Mechanics 

      Deffner, Sebastian; Saxena, Avadh (American Physical Society (APS), 2015-04-13)
      We show that the quantum Jarzynski equality generalizes to PT-symmetric quantum mechanics with unbroken PT symmetry. In the regime of broken PT symmetry, the Jarzynski equality does not hold as also the CPT norm is not ...
    • Quantum work statistics of linear and nonlinear parametric oscillators 

      Deffner, Sebastian; Abah, Obinna; Lutz, Eric (Elsevier, 2010-06-18)
      We consider the nonequilibrium work distribution of a quantum oscillator with modulated angular frequency. We examine the discrete-to-continuous transition of the distribution as the temperature and the degree of nonadiabaticity ...
    • Geometric quantum speed limits: a case for Wigner phase space 

      Deffner, Sebastian (IOP, 2017-10-20)
      The quantum speed limit is a fundamental upper bound on the speed of quantum evolution. However, the actual mathematical expression of this fundamental limit depends on the choice of a measure of distinguishability of ...
    • Thermodynamic length for far-from-equilibrium quantum systems 

      Deffner, Sebastian; Lutz, Eric (American Physical Society (APS), 2013-02-28)
      We consider a closed quantum system initially at thermal equilibrium and driven by arbitrary external parameters. We derive a lower bound on the entropy production which we express in terms of the Bures angle between the ...
    • Information-driven current in a quantum Maxwell demon 

      Deffner, Sebastian (American Physical Society (APS), 2013-12-16)
      We describe a minimal model of a quantum Maxwell demon obeying Hamiltonian dynamics. The model is solved exactly, and we analyze its steady-state behavior. We find that writing information to a quantum memory induces a ...
    • Quantum entropy production in phase space 

      Deffner, Sebastian (IOP, 2013-08-12)
      A fluctuation theorem for the nonequilibrium entropy production in quantum phase space is derived, which enables the consistent thermodynamic description of arbitrary quantum systems, open and closed. The new treatment ...
    • Demonstration of entanglement assisted invariance on IBM’s quantum experience 

      Deffner, Sebastian (Cell Press, 2017-11-03)
      Quantum entanglement is among the most fundamental, yet from classical intuition also most surprising properties of the fully quantum nature of physical reality. We report several experiments performed on IBM's Quantum ...
    • Holevo's bound from a general quantum fluctuation theorem 

      Kafri, Dvir; Deffner, Sebastian (American Physical Society (APS), 2012-10-22)
      We give a derivation of Holevo's bound using an important result from nonequilibrium statistical physics, the fluctuation theorem. To do so we develop a general formalism of quantum fluctuation theorems for two-time ...
    • Environment-Assisted Speed-up of the Field Evolution in Cavity Quantum Electrodynamics 

      Cimmarusti, A. D.; Yan, Z.; Patterson, B. D.; Corcos, L. P.; Orozco, L. A.; Deffner, S. (American Physical Society (APS), 2015-06-11)
      We measure the quantum speed of the state evolution of the field in a weakly driven optical cavity QED system. To this end, the mode of the electromagnetic field is considered as a quantum system of interest with a ...
    • Thermodynamic universality of quantum Carnot engines 

      Gardas, Bartłomiej; Deffner, Sebastian (American Physical Society (APS), 2015-10-12)
      The Carnot statement of the second law of thermodynamics poses an upper limit on the efficiency of all heat engines. Recently, it has been studied whether generic quantum features such as coherence and quantum entanglement ...
    • Trade-Off Between Speed and Cost in Shortcuts to Adiabaticity 

      Campbell, Steve; Deffner, Sebastian (American Physical Society (APS), 2017-03-08)
      Achieving effectively adiabatic dynamics is a ubiquitous goal in almost all areas of quantum physics. Here, we study the speed with which a quantum system can be driven when employing transitionless quantum driving. As a ...
    • Energy–time uncertainty relation for driven quantum systems 

      Deffner, Sebastian; Lutz, Eric (IOP, 2013-07-29)
      We derive generalizations of the energy–time uncertainty relation for driven quantum systems. Using a geometric approach based on the Bures length between mixed quantum states, we obtain explicit expressions for the quantum ...
    • Nonequilibrium work distribution of a quantum harmonic oscillator 

      Deffner, Sebastian; Lutz, Eric (American Physical Society (APS), 2008-02-27)
      We calculate analytically the work distribution of a quantum harmonic oscillator with arbitrary time-dependent angular frequency. We provide detailed expressions for the work probability density for adiabatic and nonadiabatic ...
    • Information Processing and the Second Law of Thermodynamics: An Inclusive, Hamiltonian Approach 

      Deffner, Sebastian; Jarzynski, Christopher (American Physical Society (APS), 2013-10-17)
      We obtain generalizations of the Kelvin-Planck, Clausius, and Carnot statements of the second law of thermodynamics for situations involving information processing. To this end, we consider an information reservoir ...
    • Nonequilibrium Entropy Production for Open Quantum Systems 

      Deffner, Sebastian; Lutz, Eric (American Physical Society (APS), 2011-09-30)
      We consider open quantum systems weakly coupled to a heat reservoir and driven by arbitrary time-dependent parameters. We derive exact microscopic expressions for the nonequilibrium entropy production and entropy production ...