Efficient implementation of single particle Hamiltonians in exponentially reduced qubit space

Fuente: arXiv
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Hauptverfasser: Plesch, Martin, Friák, Martin, Mohammad, Ijaz Ahamed
Format: Preprint
Veröffentlicht: 2026
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author Plesch, Martin
Friák, Martin
Mohammad, Ijaz Ahamed
author_facet Plesch, Martin
Friák, Martin
Mohammad, Ijaz Ahamed
contents Current and near-term quantum hardware is constrained by limited qubit counts, circuit depth, and the high cost of repeated measurements. We address these challenges for solid state Hamiltonians by introducing a logarithmic-qubit encoding that maps a system with $N$ physical sites onto only $\lceil \log_2 N \rceil$ qubits while maintaining a clear correspondence with the underlying physical model. Within this reduced register, we construct a compatible variational circuit and a Gray-code-inspired measurement strategy whose number of global settings grows only logarithmically with system size. To quantify the overall hardware load, we introduce a volumetric efficiency metric that combines the number of qubit, circuit depth, and the number of measurement settings into a single measure, expressing the overall computation costs. Using this metric, we show that the total space-time-sampling volume required in a variational loop can be reduced dramatically from $N^2$ to $(logN)^3$ for hardware efficient ansatz, allowing an exponential reduction in time and size of the quantum hardware. These results demonstrate that large, structured solid-state Hamiltonians can be simulated on substantially smaller quantum registers with controlled sampling overhead and manageable circuit complexity, extending the reach of variational quantum algorithms on near-term devices.
format Preprint
id arxiv_https___arxiv_org_abs_2601_00247
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Efficient implementation of single particle Hamiltonians in exponentially reduced qubit space
Plesch, Martin
Friák, Martin
Mohammad, Ijaz Ahamed
Quantum Physics
Current and near-term quantum hardware is constrained by limited qubit counts, circuit depth, and the high cost of repeated measurements. We address these challenges for solid state Hamiltonians by introducing a logarithmic-qubit encoding that maps a system with $N$ physical sites onto only $\lceil \log_2 N \rceil$ qubits while maintaining a clear correspondence with the underlying physical model. Within this reduced register, we construct a compatible variational circuit and a Gray-code-inspired measurement strategy whose number of global settings grows only logarithmically with system size. To quantify the overall hardware load, we introduce a volumetric efficiency metric that combines the number of qubit, circuit depth, and the number of measurement settings into a single measure, expressing the overall computation costs. Using this metric, we show that the total space-time-sampling volume required in a variational loop can be reduced dramatically from $N^2$ to $(logN)^3$ for hardware efficient ansatz, allowing an exponential reduction in time and size of the quantum hardware. These results demonstrate that large, structured solid-state Hamiltonians can be simulated on substantially smaller quantum registers with controlled sampling overhead and manageable circuit complexity, extending the reach of variational quantum algorithms on near-term devices.
title Efficient implementation of single particle Hamiltonians in exponentially reduced qubit space
topic Quantum Physics
url https://arxiv.org/abs/2601.00247