# Strongly measuring qubit quasiprobabilities behind out-of-time-ordered correlators

## TL;DR

This paper proposes a method to experimentally measure nonclassical quasiprobability distributions related to out-of-time-ordered correlators in many-qubit systems, enhancing understanding of quantum information scrambling.

## Contribution

It introduces a practical circuit-based approach to obtain quasiprobability distributions associated with OTOCs, enabling nuanced analysis of quantum scrambling.

## Key findings

- Method successfully extracts QPDs using three and four measurement circuits.
- Stronger measurements reduce experimental resources needed.
- The approach reveals detailed features of quantum information scrambling.

## Abstract

Out-of-time-ordered correlators (OTOCs) have been proposed as a tool to witness quantum information scrambling in many-body system dynamics. These correlators can be understood as averages over nonclassical multi-time quasi-probability distributions (QPDs). These QPDs have more information, and their nonclassical features witness quantum information scrambling in a more nuanced way. However, their high dimensionality and nonclassicality make QPDs challenging to measure experimentally. We focus on the topical case of a many-qubit system and show how to obtain such a QPD in the laboratory using circuits with three and four sequential measurements. Averaging distinct values over the same measured distribution reveals either the OTOC or parameters of its QPD. Stronger measurements minimize experimental resources despite increased dynamical disturbance.