TY - JOUR

T1 - Coherence-enhanced efficiency of feedback-driven quantum engines

AU - Brandner, Kay

AU - Bauer, Michael

AU - Schmid, Michael T.

AU - Seifert, Udo

N1 - Publisher Copyright:
© 2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

PY - 2015/6/4

Y1 - 2015/6/4

N2 - A genuine feature of projective quantum measurements is that they inevitably alter the mean energy of the observed system if the measured quantity does not commute with the Hamiltonian. Compared to the classical case, Jacobs proved that this additional energetic cost leads to a stronger bound on the work extractable after a single measurement from a system initially in thermal equilibrium (2009 Phys. Rev. A 80 012322). Here, we extend this bound to a large class of feedback-driven quantum engines operating periodically and in finite time. The bound thus implies a natural definition for the efficiency of information to work conversion in such devices. For a simple model consisting of a laser-driven two-level system, we maximize the efficiency with respect to the observable whose measurement is used to control the feedback operations. We find that the optimal observable typically does not commute with the Hamiltonian and hence would not be available in a classical two level system. This result reveals that periodic feedback engines operating in the quantum realm can exploit quantum coherences to enhance efficiency.

AB - A genuine feature of projective quantum measurements is that they inevitably alter the mean energy of the observed system if the measured quantity does not commute with the Hamiltonian. Compared to the classical case, Jacobs proved that this additional energetic cost leads to a stronger bound on the work extractable after a single measurement from a system initially in thermal equilibrium (2009 Phys. Rev. A 80 012322). Here, we extend this bound to a large class of feedback-driven quantum engines operating periodically and in finite time. The bound thus implies a natural definition for the efficiency of information to work conversion in such devices. For a simple model consisting of a laser-driven two-level system, we maximize the efficiency with respect to the observable whose measurement is used to control the feedback operations. We find that the optimal observable typically does not commute with the Hamiltonian and hence would not be available in a classical two level system. This result reveals that periodic feedback engines operating in the quantum realm can exploit quantum coherences to enhance efficiency.

KW - coherence

KW - quantum information engine

KW - quantum thermodynamics

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U2 - 10.1088/1367-2630/17/6/065006

DO - 10.1088/1367-2630/17/6/065006

M3 - Article

AN - SCOPUS:84951300226

VL - 17

JO - New Journal of Physics

JF - New Journal of Physics

SN - 1367-2630

IS - 6

M1 - 065006

ER -