4 research outputs found
Thermodynamics of quantum Brownian motion with internal degrees of freedom: the role of entanglement in the strong-coupling quantum regime
We study the influence of entanglement on the relation between the
statistical entropy of an open quantum system and the heat exchanged with a low
temperature environment. A model of quantum Brownian motion of the
Caldeira-Leggett type - for which a violation of the Clausius inequality has
been stated by Th.M. Nieuwenhuizen and A.E. Allahverdyan [Phys. Rev. E 66,
036102 (2002)] - is reexamined and the results of the cited work are put into
perspective. In order to address the problem from an information theoretical
viewpoint a model of two coupled Brownian oscillators is formulated that can
also be viewed as a continuum version of a two-qubit system. The influence of
an additional internal coupling parameter on heat and entropy changes is
described and the findings are compared to the case of a single Brownian
particle.Comment: 10 pages, 11 figure
Finite quantum dissipation: the challenge of obtaining specific heat
We consider a free particle coupled with finite strength to a bath and
investigate the evaluation of its specific heat. A harmonic oscillator bath of
Drude type with cutoff frequency omega_D is employed to model an ohmic friction
force with dissipation strength gamma. Two scenarios for obtaining specific
heat are presented. The first one uses the measurement of the kinetic energy of
the free particle while the second one is based on the reduced partition
function. Both descriptions yield results which are consistent with the Third
Law of thermodynamics. Nevertheless, the two methods produce different results
that disagree even in their leading quantum corrections at high temperatures.
We also consider the regime where the cutoff frequency is smaller than the
friction strength, i.e. omega_D<gamma. There, we encounter puzzling results at
low temperatures where the specific heat based on the thermodynamic
prescription becomes negative. This anomaly is rooted in an ill-defined density
of states of the damped free particle which assumes unphysical negative values
when gamma/omega_D>1.Comment: 16 pages, 4 figure
Fluctuation theorems in driven open quantum systems
The characteristic function for the joint measurement of the changes of two
commuting observables upon an external forcing of a quantum system is derived.
In particular, the statistics of the internal energy, the exchanged heat and
the work of a quantum system that {\it weakly} couples to its environment is
determined in terms of the energy changes of the system and the environment due
to the action of a classical, external force on the system. If the system and
environment initially are in a canonical equilibrium, the work performed on the
system is shown to satisfy the Tasaki-Crooks theorem and the Jarzynski
equality.Comment: 12 page
Information and entropy in quantum Brownian motion: Thermodynamic entropy versus von Neumann entropy
We compare the thermodynamic entropy of a quantum Brownian oscillator derived
from the partition function of the subsystem with the von Neumann entropy of
its reduced density matrix. At low temperatures we find deviations between
these two entropies which are due to the fact that the Brownian particle and
its environment are entangled. We give an explanation for these findings and
point out that these deviations become important in cases where statements
about the information capacity of the subsystem are associated with
thermodynamic properties, as it is the case for the Landauer principle.Comment: 8 pages, 7 figure