Quantum computational advantage attested by nonlocal games with the cyclic cluster state

TL;DR

This paper introduces Bell-type nonlocal games to demonstrate quantum advantage using cyclic cluster states, validated through experiments on a trapped-ion quantum computer, providing scalable benchmarks for quantum computing.

Contribution

It presents a novel set of nonlocal games that can unconditionally prove quantum advantage in a hardware-agnostic way, with experimental validation on a six-qubit system.

Findings

Fidelity of 60.6% before correction, 66.4% after correction.

Experimental results surpass classical Bell bounds, nearing depth-1 classical circuit limits.

Provides scalable benchmarks for pre-fault-tolerant quantum computers.

Abstract

We propose a set of Bell-type nonlocal games that can be used to prove an unconditional quantum advantage in an objective and hardware-agnostic manner. In these games, the circuit depth needed to prepare a cyclic cluster state and measure a subset of its Pauli stabilizers on a quantum computer is compared to that of classical Boolean circuits with the same, nearest-neighboring gate connectivity. Using a circuit-based trapped-ion quantum computer, we prepare and measure a six-qubit cyclic cluster state with an overall fidelity of 60.6% and 66.4%, before and after correcting for measurement-readout errors, respectively. Our experimental results indicate that while this fidelity readily passes conventional (or depth-0) Bell bounds for local hidden-variable models, it is on the cusp of demonstrating a higher probability of success than what is possible by depth-1 classical circuits. Our games offer a practical and scalable set of quantitative benchmarks for quantum computers in the pre-fault-tolerant regime as the number of qubits available increases.