Strengthening weak measurements of qubit out-of-time-order correlators
Justin Dressel, José Raúl González Alonso, Mordecai Waegell, Nicole Yunger Halpern · Physical Review A · 2018
For systems of controllable qubits, we provide a method for experimentally obtaining a useful class of multitime correlators using sequential generalized measurements of arbitrary strength. Specifically, if a correlator can be expressed as an average of nested (anti)commutators of operators that square to the identity, then that correlator can be determined exactly from the average of a measurement sequence. As a relevant example, we provide quantum circuits for measuring multiqubit out-of-time-order correlators using optimized control-$Z$ or $\mathit{ZX}$-90 two-qubit gates common in superconducting transmon implementations.