Reexamination of pure qubit work extraction
File(s)
Published version
Author(s)
Frenzel, MF
Jennings, D
Rudolph, T
Type
Journal Article
Abstract
Many work extraction or information erasure processes in the literature involve the raising and lowering
of energy levels via external fields. But even if the actual system is treated quantum mechanically, the field
is assumed to be classical and of infinite strength, hence not developing any correlations with the system or
experiencing back-actions. We extend these considerations to a fully quantum mechanical treatment by studying
a spin-1/2 particle coupled to a finite-sized directional quantum reference frame, a spin-l system, which models
an external field. With this concrete model together with a bosonic thermal bath, we analyze the back-action
a finite-size field suffers during a quantum-mechanical work extraction process and the effect this has on the
extractable work and highlight a range of assumptions commonly made when considering such processes. The
well-known semiclassical treatment of work extraction from a pure qubit predicts a maximum extractable work
W = kT log 2 for a quasistatic process, which holds as a strict upper bound in the fully quantum mechanical case
and is attained only in the classical limit. We also address the problem of emergent local time dependence in a
joint system with a globally fixed Hamiltonian.
of energy levels via external fields. But even if the actual system is treated quantum mechanically, the field
is assumed to be classical and of infinite strength, hence not developing any correlations with the system or
experiencing back-actions. We extend these considerations to a fully quantum mechanical treatment by studying
a spin-1/2 particle coupled to a finite-sized directional quantum reference frame, a spin-l system, which models
an external field. With this concrete model together with a bosonic thermal bath, we analyze the back-action
a finite-size field suffers during a quantum-mechanical work extraction process and the effect this has on the
extractable work and highlight a range of assumptions commonly made when considering such processes. The
well-known semiclassical treatment of work extraction from a pure qubit predicts a maximum extractable work
W = kT log 2 for a quasistatic process, which holds as a strict upper bound in the fully quantum mechanical case
and is attained only in the classical limit. We also address the problem of emergent local time dependence in a
joint system with a globally fixed Hamiltonian.
Date Issued
2014-11-18
Date Acceptance
2014-06-23
Citation
Physical Review E, 2014, 90 (5)
ISSN
1539-3755
Publisher
American Physical Society
Journal / Book Title
Physical Review E
Volume
90
Issue
5
Copyright Statement
© 2014 The American Physical Society
Subjects
Science & Technology
Physical Sciences
Physics, Fluids & Plasmas
Physics, Mathematical
Physics
GRAVITATIONAL-FIELD
QUANTUM INFORMATION
STATES
THERMODYNAMICS
PRINCIPLE
NEUTRON
Publication Status
Published
Article Number
052136