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arXiv · 2512.13580

Optimised Fermion-Qubit Encodings for Quantum Simulation with Reduced Transpiled Circuit Depth

Michael Williams de la Bastida·Thomas M. Bickley·Peter V. Coveney
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Abstract

Simulation of fermionic Hamiltonians with gate-based quantum computers requires the selection of an encoding from fermionic operators to quantum gates, the most widely used being the Jordan-Wigner transform. Many alternative encodings exist, with quantum circuits and simulation results being sensitive to choice of encoding, device connectivity and Hamiltonian characteristics. Non-stochastic optimisation of the ternary tree class of encodings to date has targeted either the device or Hamiltonian. We develop a deterministic method which optimises ternary tree encodings without changing the underlying tree structure. This enables reduction in Pauli-weight without ancillae or additional swap-gate overhead. We demonstrate this method for a variety of encodings, including those which are derived from the qubit connectivity graph of a quantum computer. Numerical results for a suite of standard encoding methods applied to water in the STO-3G basis indicate that our method reduces qDRIFT circuit depths on average by 24.7% and 26.5% for untranspiled and transpiled circuits respectively.

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Michael Williams de la Bastida, Thomas M. Bickley, Peter V. Coveney. 2026-04-29. Optimised Fermion-Qubit Encodings for Quantum Simulation with Reduced Transpiled Circuit Depth. https://doi.org/10.1088/2058-9565%2Fae9b40

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