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Optimal work extraction from quantum states by photo-assisted Cooper pair tunneling

  • Niels Lörch
  • Christoph Bruder
  • Nicolas Brunner
  • Patrick P. Hofer
Publishing year: 2018-06-27
Language: English
Publication/Series: Quantum Science and Technology
Volume: 3
Issue: 3
Document type: Journal article
Publisher: Institute of Physics Publishing

Abstract english

The theory of quantum thermodynamics predicts fundamental bounds on work extraction from quantum states. As these bounds are derived in a very general and abstract setting, it is unclear how relevant they are in an experimental context, where control is typically limited. Here we address this question by showing that optimal work extraction is possible for a realistic engine. The latter consists of a superconducting circuit, where a LC-resonator is coupled to a Josephson junction. The oscillator state fuels the engine, providing energy absorbed by Cooper pairs, thus producing work in the form of an electrical current against an external voltage bias. We show that this machine can extract the maximal amount of work from all Gaussian and Fock states. Furthermore, we consider work extraction from a continuously stabilized oscillator state. In both scenarios, coherence between energy eigenstates is beneficial, increasing the power output of the machine. This is possible because the phase difference across the Josephson junction provides a phase reference.


  • Physical Sciences
  • inelastic cooper pair tunneling
  • mesoscopic physics
  • quantum thermodynamics
  • resource theory
  • work extraction


  • ISSN: 2058-9565
Portrait of Patrick Potts
E-mail: patrick [dot] potts [at] teorfys [dot] lu [dot] se

Postdoctoral fellow

Mathematical Physics


Postdoctoral fellow