Test of the unitary coupled-cluster variational quantum eigensolver for a simple strongly correlated condensed-matter system

Abstract

The variational quantum eigensolver has been proposed as a low-depth quantum circuit that can be employed to examine strongly correlated systems on today's noisy intermediate-scale quantum computers. We examine details associated with the factorized form of the unitary coupled-cluster variant of this algorithm. We apply it to a simple strongly correlated condensed-matter system with nontrivial behavior---the four-site Hubbard model at half filling. This work show some of the subtle issues one needs to take into account when applying this algorithm in practice, especially to condensed-matter systems.

arXiv comment12 pages, 4 figures, conference proceedings for ECSN-2019

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• Decomposition of high-rank factorized unitary coupled-cluster operators using ancilla and multi-qubit controlled low-rank counterparts
• Sparse-Hamiltonian approach to the time evolution of molecules on quantum computers
• Efficient application of the factorized form of the unitary coupled-cluster ansatz for the variational quantum eigensolver algorithm by using linear combination of unitaries
• Quantum Simulation of Molecules without Fermionic Encoding of the Wave Function
• Encoding strongly-correlated many-boson wavefunctions on a photonic quantum computer: application to the attractive Bose-Hubbard model