aiqbench analysis
This research presents Q-FVO, a novel method for fragmenting virtual orbitals in quantum chemistry calculations to significantly lower qubit counts. By partitioning localized spaces into chemically motivated fragments, the approach reduces circuit depth while maintaining high accuracy across various molecular benchmarks. This advancement directly addresses critical resource constraints, making complex correlated simulations more feasible on near-term quantum hardware.
Fragmentation of Virtual Orbitals for Quantum Computing: Reducing Qubit Requirements through Many-Body Expansion
arXiv:2510.20950v2 Announce Type: replace Abstract: We introduce quantum virtual-orbital fragmentation (Q-FVO), a systematic method for reducing the largest active space in correlated quantum-chemistry calculations. The complete occupied space is retained, the localized virtual space is partitioned into chemically motivated fragments, and the correlation energy is recovered through an inclusion-exclusion many-body expansion. Across six molecular benchmarks, the largest one-body Q-FVO calculations reduce the qubit requirement by 46 to 66 percent, while two-body calculations reduce it by approximately 31 to 42 percent relative to the corresponding unfragmented spaces. Two-body expansions recover most of the correlation energy, with errors of 0.9 to 7.5 kcal/mol; three-body expansions are below 1 kcal/mol for all CCSD tests and remain below 2 kcal/mol at CCSD(T). Illustrative statevector UCCSD calculations also reduce implementation-reported circuit depth while retaining accuracy below 1 kcal/mol. Q-FVO can be nested inside Q-EFMO real-space fragmentation and, in turn, the resulting cluster can be embedded in a Q-EFP environment. The hierarchy therefore reduces quantum-resource growth along three complementary dimensions: environment, molecular fragments, and virtual-orbital space.
Abstract:We introduce quantum virtual-orbital fragmentation (Q-FVO), a systematic method for reducing the largest active space in correlated quantum-chemistry calculations. The complete occupied space is retained, the localized virtual space is partitioned into chemically motivated fragments, and the correlation energy is recovered through an inclusion-exclusion many-body expansion. Across six molecular benchmarks, the largest one-body Q-FVO calculations reduce the qubit requirement by 46 to 66 percent, while two-body calculations reduce it by approximately 31 to 42 percent relative to the corresponding unfragmented spaces. Two-body expansions recover most of the correlation energy, with errors of 0.9 to 7.5 kcal/mol; three-body expansions are below 1 kcal/mol for all CCSD tests and remain below 2 kcal/mol at CCSD(T). Illustrative statevector UCCSD calculations also reduce implementation-reported circuit depth while retaining accuracy below 1 kcal/mol. Q-FVO can be nested inside Q-EFMO real-space fragmentation and, in turn, the resulting cluster can be embedded in a Q-EFP environment. The hierarchy therefore reduces quantum-resource growth along three complementary dimensions: environment, molecular fragments, and virtual-orbital space.
Quantum Physics (quant-ph); Chemical Physics (physics.chem-ph)
arXiv:2510.20950 [quant-ph]
(or arXiv:2510.20950v2 [quant-ph] for this version)
https://doi.org/10.48550/arXiv.2510.20950 Focus to learn more arXiv-issued DOI via DataCite
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Full text under the publisher's open licence · 260 words
