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QI: Fachverband Quanteninformation
QI 4: Poster: Quantum Information
QI 4.27: Poster
Montag, 5. September 2022, 18:00–20:00, P2
Quantum circuits for the preparation of spin eigenfunctions on quantum computers — •Alessandro Carbone1,2, Davide Emilio Galli2, Mario Motta3, and Barbara Jones3 — 1Theory and Simulations of Materials (THEOS), and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland — 2Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy — 3IBM Quantum, IBM Research Almaden, 650 Harry Road, San Jose, CA 95120, USA
The preparation of accurate and efficient approximations for Hamiltonian eigenstates on quantum computers is a crucial step for building the quantum advantage when studying many-body quantum systems. If we can describe molecules or materials with a coarse-grained spin Hamiltonian, spin eigenfunctions can be a useful starting point for simulations which aim to understand their electronic structure. In particular the purpose of this work is to delve into the description of the quantum circuits which prepare total spin eigenfunctions in the case of spin-1/2 systems. We investigate the balance between generality, accuracy, and computational cost in the encoding of spin eigenfunctions by quantum circuits without ancillary qubits, by pursuing two approaches: an exact recursive construction of spin eigenstates, and a heuristic variational construction of approximate spin eigenstates. We have tested the described quantum circuits on the available IBM (classical) simulators and quantum devices in the cases of 3-spin and 5-spin systems.