Accelerated Variational Quantum Eigensolver

2018/02/28 by Daochen Wang, Oscar Higgott, Stephen Brierley · 2 citations
Physics and Astronomy · #quant-ph

paper · pdf · doi:10.1103/physrevlett.122.140504

published as Phys. Rev. Lett. 122, 140504 (2019) · 11 pages

arxiv created 2019/03/25 · arxiv updated 2019/04/16

Abstract

The problem of finding the ground state energy of a Hamiltonian using a quantum computer is currently solved using either the quantum phase estimation (QPE) or variational quantum eigensolver (VQE) algorithms. For precision ε, QPE requires O(1) repetitions of circuits with depth O(1/ε), whereas each expectation estimation subroutine within VQE requires O(1/ε²) samples from circuits with depth O(1). We propose a generalised VQE algorithm that interpolates between these two regimes via a free parameter α∈[0,1] which can exploit quantum coherence over a circuit depth of O(1/ε^α) to reduce the number of samples to O(1/ε^2(1-α)). Along the way, we give a new routine for expectation estimation under limited quantum resources that is of independent interest.

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