Quantum simulations of Green's functions for small superfluid systems

• URL: http://arxiv.org/abs/2509.02272v1
• Date: Tue, 02 Sep 2025 12:48:21 GMT
• Title: Quantum simulations of Green's functions for small superfluid systems
• Authors: Samuel Aychet-Claisse, Denis Lacroix, Vittorio Somà, Jing Zhang,
• Abstract summary: An end-to-end strategy for hybrid quantum-classical computations of Green's functions in many-body systems is presented.<n>The scheme makes explicit use of the spectral representation of the Green's function.<n>Different ansatzes for the ground-state wave function, originating from either classical or quantum approaches, are tested and compared to exact calculations.
• Score: 5.901027348002322
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: An end-to-end strategy for hybrid quantum-classical computations of Green's functions in many-body systems is presented and applied to the pairing model. The scheme makes explicit use of the spectral representation of the Green's function, which entails the calculation of the $N$-body ground state as well as eigenstates and associated energies of the $(N\pm1)$-body neighbors. While the former is accessed via variational techniques, the latter are constructed by means of the quantum subspace expansion method. Different ansatzes for the ground-state wave function, originating from either classical or quantum approaches, are tested and compared to exact calculations. The resulting one-body Green's functions prove to be accurate approximations of the exact one for a large range of parameters, including across the normal-to-superfluid transition. As a byproduct, this approach yields a good description of odd systems provided that the starting even system is well reproduced by the variational ansatz.

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