507 research outputs found
Short Time Cycles of Purely Quantum Refrigerators
Four stroke Otto refrigerator cycles with no classical analogue are studied.
Extremely short cycle times with respect to the internal time scale of the
working medium characterize these refrigerators. Therefore these cycles are
termed sudden. The sudden cycles are characterized by the stable limit cycle
which is the invariant of the global cycle propagator. During their operation
the state of the working medium possesses significant coherence which is not
erased in the equilibration segments due to the very short time allocated. This
characteristic is reflected in a difference between the energy entropy and the
Von Neumann entropy of the working medium. A classification scheme for sudden
refrigerators is developed allowing simple approximations for the cooling power
and coefficient of performance.Comment: 20 pages, 12 figures. Among the figures there are 6 figures which are
double, namely with two parts, Top and Botto
A Discrete Four Stroke Quantum Heat Engine Exploring the Origin of Friction
The optimal power performance of a first principle quantum heat engine model
shows friction-like phenomena when the internal fluid Hamiltonian does not
commute with the external control field. The model is based on interacting
two-level-systems where the external magnetic field serves as a control
variable.Comment: 4 pages 3 figure
A Pulse Shaping Algorithm of a Coherent Matter Wave. Controlling Reaction Dynamics
A pulse shaping algorithm for a matter wave with the purpose of controlling a
binary reaction has been designed. The scheme is illustrated for an Eley-Rideal
reaction where an impinging matter-wave atom recombines with an adsorbed atom
on a metal surface. The wave function of the impinging atom is shaped such that
the desorbing molecule leaves the surface in a specific vibrational state.Comment: 4 pages, 5 figure
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