558 research outputs found
Entropy production in a photovoltaic cell
We evaluate entropy production in a photovoltaic cell that is modeled by four
electronic levels resonantly coupled to thermally populated field modes at
different temperatures. We use a formalism recently proposed, the so-called
multiple parallel worlds, to consistently address the nonlinearity of entropy
in terms of density matrix. Our result shows that entropy production is the
difference between two flows: a semiclassical flow that linearly depends on
occupational probabilities, and another flow that depends nonlinearly on
quantum coherence and has no semiclassical analog. We show that entropy
production in the cells depends on environmentally induced decoherence time and
energy detuning. We characterize regimes where reversal flow of information
takes place from a cold to hot bath. Interestingly, we identify a lower bound
on entropy production, which sets limitations on the statistics of dissipated
heat in the cells.Comment: 7 pages, 2 figure
Exact correspondence between Renyi entropy flows and physical flows
We present a universal relation between the flow of a Renyi entropy and the
full counting statistics of energy transfers. We prove the exact relation for a
flow to a system in thermal equilibrium that is weakly coupled to an arbitrary
time-dependent and non-equilibrium system. The exact correspondence, given by
this relation, provides a simple protocol to quantify the flows of Shannon and
Renyi entropies from the measurements of energy transfer statistics.Comment: 9 pages, 5 figure
Exact quantization of superconducting circuits
We present a theoretical description for circuits consisting of weak
anharmonic qubits coupled to cavity multimodes. We obtain a unitary
transformation that diagonalizes harmonic sector of the circuit. Weak
anharmonicity does not alter the normal mode basis, however it can modify
energy levels. We study two examples of a transmon and two transmons coupled to
bus resonator, and we determine dressed frequencies and Kerr nonlinearities in
closed form formulas. Our results are valid for arbitrary frequency detuning
and coupling within and beyond dispersive regime.Comment: 9 pages, 3 figure
Stimulated quantum phase slips from weak electromagnetic radiations in superconducting nanowires
We study the rate of quantum phase slips in an ultranarrow superconducting
nanowire exposed to weak electromagnetic radiations. The superconductor is in
the dirty limit close to the superconducting-insulating transition, where
fluxoids move in strong dissipation. We use a semiclassical approach and show
that external radiation stimulates a significant enhancement in the probability
of quantum phase slips. This can help to outline a new type of detector for
microwave to submillimetre radiations based on stimulated quantum phase slip
phenomenon.Comment: 10 pages, 9 figure
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