A new paper by Nicole Yunger Halpern, Brian Swingle and Justin Dressel combines the out-of-time-ordered correlator (OTOC) and the Kirkwood-Dirac (KD) quasiprobability.

Quantum circuit, figure 3

Quantum circuit for inferring the coarse-grained OTOC quasiprobability A from weak measurements. [Fig. 3]

Two topics, evolving rapidly in separate fields, were combined recently: the out-of-time-ordered correlator (OTOC) signals quantum-information scrambling in many-body systems. The Kirkwood-Dirac (KD) quasiprobability represents operators in quantum optics. The OTOC was shown to equal a moment of a summed quasiprobability [Yunger Halpern, Phys. Rev. A 95, 012120 (2017)]. That quasiprobability, we argue, is an extension of the KD distribution. We explore the quasiprobability’s structure from experimental, numerical, and theoretical perspectives.

This work not only illuminates the OTOC’s underpinnings, but also generalizes quasiprobability theory and motivates immediate-future weak-measurement challenges.

Read the full paper:

Nicole Yunger Halpern, Brian Swingle, and Justin Dressel, Quasiprobability behind the out-of-time-ordered correlator, Phys. Rev. A 97, 042105, Published 10 April 2018. http://resolver.caltech.edu/CaltechAUTHORS:20180411-120256215