Quantum scrambling with classical shadows

Quantum dynamics is of fundamental interest and has implications in quantum information processing. The four-point out-of-time-ordered correlator (OTOC) is traditionally used to quantify quantum information scrambling under many-body dynamics. Due to the OTOC's unusual time ordering, its measurement is challenging. We propose higher-point OTOCs to reveal early-time scrambling behavior, and present protocols to measure any higher-point OTOC using the shadow estimation method. The protocols circumvent the need for time-reversal evolution and ancillary control. They can be implemented in near-term quantum devices with single-qubit readout.

Automated summary

In this work, higher-point OTOCs are proposed to reveal early-time scrambling behavior in quantum dynamics, with protocols presented for their measurement using the shadow estimation method. These protocols offer a way to measure higher-point OTOCs without the need for time-reversal evolution and ancillary control, making them suitable for implementation in near-term quantum devices with single-qubit readout.