Device-independent prepare-and-prepare bipartite null witness dimension test with a single joint measurement

TL;DR

This paper introduces a device-independent method to test the dimensionality of bipartite quantum systems using a single joint measurement, demonstrating high precision on IBM Quantum devices and detecting deviations from qubit assumptions.

Contribution

The paper presents a novel null witness test for bipartite quantum dimension that is device-independent and uses a single joint measurement, applicable to real quantum devices.

Findings

Successfully applied to IBM Quantum devices with high precision

Detected deviations from qubit space beyond 6 standard deviations

Revealed technical imperfections affecting quantum measurements

Abstract

We propose a device-independent null witness dimensionality test with bipartite measurements and input from two separate parties. The dimension is determined from the rank of the matrix of measurements for pairs of states prepared by the parties. We have applied the test to various IBM Quantum devices. The results demonstrate extreme precision of the test, which is able to detect disagreements with the qubit (two-level) space of bipartite measurement even in the presence of technical imperfections. The deviations beyond 6 standard deviations have no simple origin and need urgent explanations to unblock progress in quantum computing.