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Accessing ground-state and excited-state energies in a many-body system after symmetry restoration using quantum computers

2022; American Physical Society; Volume: 105; Issue: 2 Linguagem: Inglês

10.1103/physrevc.105.024324

2470-0002

Edgar Andres Ruiz Guzman, Denis Lacroix,

Quantum Information and Cryptography

We explore the possibility to perform symmetry restoration with the variation after projection technique on a quantum computer followed by additional post-processing. The final goal is to develop configuration interaction techniques based on many-body trial states pre-optimized on a quantum computer. We show how the projection method used for symmetry restoration can prepare optimized states that could then be employed as initial states for quantum or hybrid quantum-classical algorithms. We use the quantum phase estimation and quantum Krylov approaches for the post-processing. The latter method combined with the quantum variation after projection (Q-VAP) leads to very fast convergence towards the ground-state energy. The possibility to access excited states energies is also discussed. Illustrations of the different techniques are made using the pairing hamiltonian.