Experimental Simulation of Larger Quantum Circuits with Fewer Superconducting Qubits

TL;DR

This paper demonstrates a circuit-cutting technique that allows the simulation of large quantum circuits with many logical qubits using only a few physical superconducting qubits, significantly improving fidelity.

Contribution

It introduces an experimental method for circuit-cutting in superconducting qubits, enabling simulation of larger quantum states with fewer qubits than traditionally required.

Findings

Successfully simulated 33-qubit linear-cluster states with 4 physical qubits per subcircuit.

Achieved a fidelity bound of 0.734 for 12-qubit states, 19% higher than direct simulation.

Proved circuit-cutting as a practical approach for scalable quantum simulation with limited qubits.

Abstract

Although near-term quantum computing devices are still limited by the quantity and quality of qubits in the so-called NISQ era, quantum computational advantage has been experimentally demonstrated. Moreover, hybrid architectures of quantum and classical computing have become the main paradigm for exhibiting NISQ applications, where low-depth quantum circuits are repeatedly applied. In order to further scale up the problem size solvable by the NISQ devices, it is also possible to reduce the number of physical qubits by "cutting" the quantum circuit into different pieces. In this work, we experimentally demonstrated a circuit-cutting method for simulating quantum circuits involving many logical qubits, using only a few physical superconducting qubits. By exploiting the symmetry of linear-cluster states, we can estimate the effectiveness of circuit-cutting for simulating up to 33-qubit linear-cluster states, using at most 4 physical qubits for each subcircuit. Specifically, for the 12-qubit linear-cluster state, we found that the experimental fidelity bound can reach as much as 0.734, which is about 19\% higher than a direct simulation {on the same} 12-qubit superconducting processor. Our results indicate that circuit-cutting represents a feasible approach of simulating quantum circuits using much fewer qubits, while achieving a much higher circuit fidelity.