- Open Access
Efficient Quantum-Enhanced Classical Simulation for Patches of Quantum Landscapes
PRX Quantum 7, 020359 – Published 12 June, 2026
DOI: https://doi.org/10.1103/fhc5-8sm6
Abstract
Understanding the capabilities of classical simulation methods is key to identifying where quantum computers are advantageous. Not only does this ensure that quantum computers are used only where necessary, but also one can potentially identify subroutines that can be offloaded onto a classical device. In this work, we show that it is always possible to generate a classical surrogate of a subregion (dubbed a “patch”) of an expectation landscape produced by a parameterized quantum circuit. That is, we provide a quantum-enhanced classical algorithm which, after simple measurements on a quantum device, allows one to classically simulate approximate expectation values of a subregion of a landscape. We provide time and sample complexity guarantees for a range of families of circuits of interest, and further numerically demonstrate our simulation algorithms on an exactly verifiable simulation of a Hamiltonian variational Ansatz and long-time dynamics simulation on a 127-qubit heavy-hex topology.
Physics Subject Headings (PhySH)
Popular Summary
Finding problems in science which are worthwhile to solve with quantum computers is a formidable challenge. It is yet unclear whether sufficiently accurate simulation of systems of interest, such as molecular dynamics and exotic materials, will even necessitate a quantum computer. This is because as experimentalists and algorithm designers devise techniques to simulate a widening pool of systems, theorists work closely behind them to classically simulate and dequantize their methods. The battle is well-intentioned; reducing or removing the quantum components of these algorithms expedites their real-world utility.
To this end, we present a “quantum-enhanced” classical method for surrogating subregions of the expectation landscape generated by a generic parametrized quantum circuit. That is, after simple measurements on a quantum device, the algorithm allows one to classically simulate approximate expectation values of patches of a landscape. We provide time and sample complexity guarantees for a range of families of circuits of interest, and further numerically demonstrate our simulation algorithms on an exactly verifiable simulation of a Hamiltonian variational Ansatz and long-time dynamics simulation on a 127-qubit heavy-hex topology. Our results can be applied to a wide range of quantum domains from variational quantum algorithms to dynamical simulation and quantum metrology.
Article Text
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