53 research outputs found
Maxwell demons in phase space
Although there is not a complete "proof" of the second law of thermo-
dynamics based on microscopic dynamics, two properties of Hamiltonian systems
have been used to prove the impossibility of work extraction from a single
thermal reservoir: Liouville's theorem and the adiabatic invariance of the
volume enclosed by an energy shell. In this paper we analyze these two
properties in the Szilard engine and other systems related with the Maxwell
demon. In particular, we recall that the enclosed volume is no longer an
adiabatic invariant in non ergodic systems and explore the consequences of this
on the second law.Comment: 14 pages, to appear in EPJS
Thermodynamic Reversibility in Feedback Processes
The sum of the average work dissipated plus the information gained during a
thermodynamic process with discrete feedback must exceed zero. We demonstrate
that the minimum value of zero is attained only by feedback-reversible
processes that are indistinguishable from their time-reversal, thereby
extending the notion of thermodynamic reversibility to feedback processes. In
addition, we prove that in every realization of a feedback-reversible process
the sum of the work dissipated and change in uncertainty is zero.Comment: 6 pages, 4, figures, accepted in EPL, expanded discussion of
thermodynamic reversibilit
Nonequilibrium potential and fluctuation theorems for quantum maps
We derive a general fluctuation theorem for quantum maps. The theorem applies
to a broad class of quantum dynamics, such as unitary evolution, decoherence,
thermalization, and other types of evolution for quantum open systems. The
theorem reproduces well-known fluctuation theorems in a single and simplified
framework and extends the Hatano-Sasa theorem to quantum nonequilibrium
processes. Moreover, it helps to elucidate the physical nature of the
environment inducing a given dynamics in an open quantum system.Comment: 10 page
Quantum fluctuation theorems for arbitrary environments: adiabatic and non-adiabatic entropy production
We analyze the production of entropy along non-equilibrium processes in
quantum systems coupled to generic environments. First, we show that the
entropy production due to final measurements and the loss of correlations obeys
a fluctuation theorem in detailed and integral forms. Second, we discuss the
decomposition of the entropy production into two positive contributions,
adiabatic and non-adiabatic, based on the existence of invariant states of the
local dynamics. Fluctuation theorems for both contributions hold only for
evolutions verifying a specific condition of quantum origin. We illustrate our
results with three relevant examples of quantum thermodynamic processes far
from equilibrium.Comment: 20 pages + 6 of appendices; 7 figures; v2: New example added (example
A) and some minor corrections; accepted in Phys. Rev.
Autonomous thermal machine for amplification and control of energetic coherence
We present a model for an autonomous quantum thermal machine comprised of two
qubits capable of manipulating and even amplifying the local coherence in a
non-degenerate external system. The machine uses only thermal resources,
namely, contact with two heat baths at different temperatures, and the external
system has a non-zero initial amount of coherence. The method we propose allows
for an interconversion between energy, both work and heat, and coherence in an
autonomous configuration working in out-of-equilibrium conditions. This model
raises interesting questions about the role of fundamental limitations on
transformations involving coherence and opens up new possibilities in the
manipulation of coherence by autonomous thermal machines.Comment: v1: 5 + 3 pages, 2 figures. v2: Restructured version with several new
results and a new appendix, 11 + 14 pages, 4 + 3 figures. v3: Improved and
corrected version with new discussions, 8 + 8 pages, 4 + 3 figure
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