We do physics partially out of a drive to understand essences. One topic whose essence merits understanding is the out-of-time-ordered correlator (OTOC). The OTOC reflects quantum manybody thermalization, chaos, and scrambling (the spread of quantum information through manybody entanglement). The OTOC, I will show, equals an average over a quasiprobability distribution. A quasiprobability resembles a probability but can become negative and nonreal. Such nonclassical values can signal nonclassical physics. The OTOC quasiprobability has several applications: Experimentally, the quasiprobability points to a scheme for measuring the OTOC (via weak measurements, which refrain from disturbing the measured system much). The quasiprobability also signals false positives in attempts to measure scrambling of open systems. Theoretically, the quasiprobability links the OTOC to uncertainty relations, to nonequilibrium statistical mechanics, and more strongly to chaos. As coarse-graining the quasiprobability yields the OTOC, the quasiprobability forms the OTOC's essence.
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Academic year 2018-2019, please join us at Spilker room 232 every Monday afternoon from 4 pm for the AP 483 & Ginzton Lab, and AMO Seminar Series.
Refreshments begin at 4 pm, seminar at 4:15 pm.
Nicole Yunger Halpern
Harvard-Smithsonian ITAMP (Inst. for Atomic, Molecular, and Optical Physics)
Harvard University Dept. of Physics