Quantum eigenstate preparation assisted by a coherent link

Physical Review A, vol. 111

Abstract

Preparing the ground state of a local Hamiltonian is a crucial problem in understanding quantum many-body systems, with applications in a variety of physics fields and connections to combinatorial optimization. While various quantum algorithms exist which can prepare the ground state with high precision and provable guarantees from an initial approximation, current devices are limited to shallow circuits. Here we consider the setting where Alice and Bob, in a distributed quantum computing architecture, want to prepare the same Hamiltonian eigenstate. We demonstrate that the circuit depth of the eigenstate preparation algorithm can be reduced when the devices can share entanglement via a coherent link. This is especially so in the case where one of them has a near-perfect eigenstate, which is more efficiently broadcast to the other device. Our approach requires only a single auxiliary qubit per device to be entangled with the outside. We show that, in the near-convergent regime, the average relative suppression of unwanted amplitudes is improved to 1 / ( 2 e ) ≈ 0.30 per run of the protocol, outperforming the average relative suppression of 1 / e ≈ 0.37 achieved with a single device alone for the same protocol.

Authors 2

1. Benjamin F. Schiffer

   Munich Center for Quantum Science and Technology · Max Planck Institute of Quantum Optics

   Affiliation as printed

   Max-Planck-Institut für Quantenoptik

   Munich Center for Quantum Science and Technology

2. Jordi Tura Aachen

   Leiden University

   Affiliation as printed

   Universiteit Leiden