Improving fermionic variational quantum eigensolvers with Majorana swap networks

Fuente: arXiv
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Auteurs principaux: Fisher, D. E., Fldzhyan, S. A., Minaev, D. V., Straupe, S. S., Saygin, M. Yu.
Format: Preprint
Publié: 2025
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author Fisher, D. E.
Fldzhyan, S. A.
Minaev, D. V.
Straupe, S. S.
Saygin, M. Yu.
author_facet Fisher, D. E.
Fldzhyan, S. A.
Minaev, D. V.
Straupe, S. S.
Saygin, M. Yu.
contents Simulating computationally hard fermionic systems is a promising application of quantum computing. However, mapping nonlocal fermionic operators to qubits often produces deep circuits, rendering such simulations impractical on near-term hardware. We introduce two Majorana swap network techniques for variational quantum eigensolvers that reduce circuit depth and two-qubit gate count, thereby limiting error accumulation. First, we develop a cyclic compilation algorithm that localizes all two-particle interaction terms in a general fermionic Hamiltonian that contains $\mathcal{O}(n^4)$ such terms, using only $\mathcal{O}(n^3)$ auxiliary Majorana-swap gates, where $n$ is the number of fermionic modes. This algorithm targets all-to-all qubit connectivity (e.g., trapped-ion processors) and can be used to compactify UCCGSD circuits. Second, we design a Majorana swap network for the UpCCGSD variational ansatz, which is already more compact than UCCGSD. Our network achieves asymptotic reductions in circuit depth and gate count of approximately 50% and 20%, respectively, under all-to-all connectivity. For the more restricted $2\times N$ connectivity, the reductions are even larger -- about 55% (circuit depth) and 40% (gate count). These improvements translate directly into increased robustness to hardware noise, as demonstrated by numerical simulations on representative examples.
format Preprint
id arxiv_https___arxiv_org_abs_2509_07855
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Improving fermionic variational quantum eigensolvers with Majorana swap networks
Fisher, D. E.
Fldzhyan, S. A.
Minaev, D. V.
Straupe, S. S.
Saygin, M. Yu.
Quantum Physics
Simulating computationally hard fermionic systems is a promising application of quantum computing. However, mapping nonlocal fermionic operators to qubits often produces deep circuits, rendering such simulations impractical on near-term hardware. We introduce two Majorana swap network techniques for variational quantum eigensolvers that reduce circuit depth and two-qubit gate count, thereby limiting error accumulation. First, we develop a cyclic compilation algorithm that localizes all two-particle interaction terms in a general fermionic Hamiltonian that contains $\mathcal{O}(n^4)$ such terms, using only $\mathcal{O}(n^3)$ auxiliary Majorana-swap gates, where $n$ is the number of fermionic modes. This algorithm targets all-to-all qubit connectivity (e.g., trapped-ion processors) and can be used to compactify UCCGSD circuits. Second, we design a Majorana swap network for the UpCCGSD variational ansatz, which is already more compact than UCCGSD. Our network achieves asymptotic reductions in circuit depth and gate count of approximately 50% and 20%, respectively, under all-to-all connectivity. For the more restricted $2\times N$ connectivity, the reductions are even larger -- about 55% (circuit depth) and 40% (gate count). These improvements translate directly into increased robustness to hardware noise, as demonstrated by numerical simulations on representative examples.
title Improving fermionic variational quantum eigensolvers with Majorana swap networks
topic Quantum Physics
url https://arxiv.org/abs/2509.07855