10 research outputs found
Thermodynamical Control by Frequent Quantum Measurements
Heat flow between a large ``bath'' and a smaller system brings them
progressively closer to thermal equilibrium while increasing their entropy.
Deviations from this trend are fluctuations involving a small fraction of a
statistical ensemble of systems interacting with the bath: in this respect,
quantum and classical thermodynamics are in agreement. Can there be drastic
differences between them? Here we address a distinctly quantum mechanical
setting that displays such differences: disturbances of thermal equilibrium
between two-level systems (TLS) and a bath by frequent and brief quantum
(non-demolishing) measurements of the TLS energy-states. If the measurements
are frequent enough to induce either the Zeno or the anti-Zeno regime, namely,
the slowdown or speedup of the TLS relaxation, then the resulting entropy and
temperature of both the system and the bath are found to be completely
unrelated to what is expected by standard thermodynamical rules that hold for
memoryless baths. The practical advantage of these anomalies is the possibility
of very fast control of heat and entropy, allowing cooling and
state-purification of quantum systems much sooner than their thermal
equilibration time.Comment: 10 Pages. Pre-submission version of Nature {\bf 452}, 724 (2008).
Includes Supplementary Informatio