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arXiv · 2505.02984

Closed-Form Expressions for Unitaries of Spin-Adapted Fermionic Operators

Ilias Magoulas·Francesco A. Evangelista
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Abstract

One of the open challenges in quantum computing simulations of problems of chemical interest is the proper enforcement of spin symmetry. Efficient quantum circuits implementing unitaries generated by spin-adapted operators remain elusive, while na\"ive Trotterization schemes break spin symmetry. In this work, we analyze the mathematical structure of spin-adapted operators and derive closed-form expressions for unitaries generated by singlet spin-adapted generalized single and double excitations. These results represent significant progress toward the economical enforcement of spin symmetry in quantum simulations.

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Ilias Magoulas, Francesco A. Evangelista. 2025-05-05. Closed-Form Expressions for Unitaries of Spin-Adapted Fermionic Operators. https://arxiv.org/abs/2505.02984

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