Observation of entanglement negativity transition of pseudo-random mixed states

TL;DR

This study experimentally observes entanglement transitions in pseudo-random multi-qubit states using a superconducting processor, revealing phase changes in negativity spectra as system parameters vary.

Contribution

First experimental demonstration of entanglement transition in pseudo-random states of multi-qubit systems using superconducting quantum circuits.

Findings

Identified three distinct entanglement phases via negativity spectra.

Observed phase transitions by varying environment and subsystem sizes.

Characterized circuit randomness with Porter-Thomas distribution comparison.

Abstract

Multipartite entanglement is a key resource for quantum computation. It is expected theoretically that entanglement transition may happen for multipartite random quantum states, however, which is still absent experimentally. Here, we report the observation of entanglement transition quantified by negativity using a fully connected 20-qubit superconducting processor. We implement multi-layer pseudo-random circuits to generate pseudo-random pure states of 7 to 15 qubits. Then, we investigate negativity spectra of reduced density matrices obtained by quantum state tomography for 6 qubits.Three different phases can be identified by calculating logarithmic negativities based on the negativity spectra. We observe the phase transitions by changing the sizes of environment and subsystems. The randomness of our circuits can be also characterized by quantifying the distance between the distribution of output bit-string probabilities and Porter-Thomas distribution. Our simulator provides a powerful tool to generate random states and understand the entanglement structure for multipartite quantum systems.