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CAMP: Truly quantum Gibbs: Thermal state of a system whose charges don’t commute

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Nicole Yunger Halpern, Harvard University
When
04 December 2018 from 3:30 PM to 4:30 PM
Where
339 Davey Laboratory
Contact Name
Marcos Rigol
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The grand canonical ensemble lies at the core of statistical mechanics. A small system thermalizes to this state while exchanging heat and particles with a bath. A quantum system may exchange quantities, or “charges,” represented by operators that fail to commute. Whether such a system thermalizes, and what form the thermal state has, require quantum extensions of thermodynamics. We characterize this state in three ways: First, we generalize the system-and-bath microcanonical ensemble to an approximate microcanonical ensemble, to accommodate the noncommutation. Tracing out the bath yields the system’s thermal state. Second, this thermal state is expected to be the fixed point of typical dynamics. Finally, the thermal state is completely passive (unable to output thermodynamic work) in an information-theoretic model for thermodynamics. This study opens new avenues into equilibrium in the presence of quantum noncommutation.

 

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