Applicability and Limitations of Quantum Circuit Cutting in Classical State-Vector Simulation

TL;DR

This paper investigates the effectiveness of quantum circuit cutting in classical state-vector simulation, deriving conditions for speedup and validating them through experiments up to 30 qubits.

Contribution

It provides a theoretical framework for when circuit cutting reduces simulation time and offers practical guidelines for its use in large quantum circuit simulations.

Findings

Speedup conditions are derived and validated up to 24 qubits.

Crossovers at 18 and 22 qubits indicate when merging surpasses cutting.

Cutting extends feasible qubit count by 4-6 within a 10-minute limit.

Abstract

Circuit cutting partitions a large quantum circuit into smaller subcircuits that can be executed independently and recombined by classical post-processing. In classical state-vector simulation with full-state reconstruction, the runtime is governed by a trade-off between reduced subcircuit size and the overheads of exponentially many subcircuits and full-state reconstruction. For equal partitioning, we derive threshold conditions on the number of cuts below which cutting reduces the wall-clock time. State-vector experiments validate the predicted speedup boundary up to 24 qubits, and a runtime breakdown up to 30 qubits identifies crossovers at $q \approx 18$ and $q \approx 22$ where merging overtakes first preprocessing and then subcircuit simulation. As a practical guideline, we show that under a 10-minute wall-clock budget, two-way cutting extends the maximum feasible qubit count by 4 to 6 qubits relative to simulation without cutting.