Encoding strongly-correlated many-boson wavefunctions on a photonic quantum computer: application to the attractive Bose-Hubbard model

TL;DR

This paper demonstrates that continuous-variable photonic quantum circuits can efficiently encode the ground states of strongly correlated many-boson systems, specifically the attractive Bose-Hubbard model, with high fidelity using few layers.

Contribution

It introduces two novel CV quantum circuit ansatze for bosonic systems and evaluates their effectiveness in encoding ground states and performing variational energy minimization.

Findings

Achieved over 99% fidelity in encoding ground states

Efficient encoding with few layers across all many-body regimes

Initial assessment of variational quantum eigensolver for bosons

Abstract

Variational quantum algorithms (VQA) are considered as some of the most promising methods to determine the properties of complex strongly correlated quantum many-body systems, especially from the perspective of devices available in the near term. In this context, the development of efficient quantum circuit ansatze to encode a many-body wavefunction is one of the keys for the success of a VQA. Great efforts have been invested to study the potential of current quantum devices to encode the eigenstates of fermionic systems, but little is known about the encoding of bosonic systems. In this work, we investigate the encoding of the ground state of the (simple but rich) attractive Bose-Hubbard model using a Continuous-Variable (CV) photonic-based quantum circuit. We introduce two different ansatz architectures and demonstrate that the proposed continuous variable quantum circuits can efficiently encode (with a fidelity higher than 99%) the strongly correlated many-boson wavefunction with just a few layers, in all many-body regimes and for different number of bosons and initial states. Beyond the study of the suitability of the ansatz to approximate the ground states of many-boson systems, we also perform initial evaluations of the use of the ansatz in a variational quantum eigensolver algorithm to find it through energy minimization. To this end we also introduce a scheme to measure the Hamiltonian energy in an experimental system, and study the effect of sampling noise.