Variational Embeddings for Many Body Quantum Systems

TL;DR

This paper introduces a variational method for representing complex quantum systems by combining classical and quantum computing resources, enabling efficient and accurate modeling of many-body quantum phenomena.

Contribution

It presents a novel variational scheme that integrates classical and quantum devices for modeling composite quantum systems with varying accuracy requirements.

Findings

Effective representation of spin chains demonstrated

Successful application to small molecules shown

Insights into accuracy and computational efficiency provided

Abstract

We propose a variational scheme to represent composite quantum systems using multiple parameterized functions of varying accuracies on both classical and quantum hardware. The approach follows the variational principle over the entire system, and is naturally suited for scenarios where an accurate description is only needed in a smaller subspace. We show how to include quantum devices as high-accuracy solvers on these correlated degrees of freedom, while handling the remaining contributions with a classical device. We demonstrate the effectiveness of the protocol on spin chains and small molecules and provide insights into its accuracy and computational cost.