Quantum Neural Network States: A Brief Review of Methods and Applications

TL;DR

This paper reviews how neural networks, especially Boltzmann machines, are used to represent and analyze quantum many-body states, addressing the exponential complexity of quantum systems with modern neural network techniques.

Contribution

It provides a comprehensive overview of neural network methods for quantum state representation, including their properties, applications, and relation to tensor networks.

Findings

Neural networks can effectively represent quantum many-body states.

Neural network states show promising entanglement and representational capabilities.

Applications include quantum state tomography and classical simulation of quantum computing.

Abstract

One of the main challenges of quantum many-body physics is that the dimensionality of the Hilbert space grows exponentially with the system size, which makes it extremely difficult to solve the Schr\"{o}dinger equations of the system. But typically, many physical systems have a simplified internal structure which makes the parameters needed to characterize their ground states exponentially smaller. This makes many numerical methods possible in capture the physics of the system. Among these modern numerical techniques, neural networks, which show great power in approximating functions and extracting features of the big data, are now attracting many interests. Neural network representation of quantum many-body states shows great potential in solving some traditionally difficult quantum problems involving large number of freedoms. In this work, we briefly review the progress of using the artificial neural network to build quantum many-body ansatz states. We take Boltzmann machine representation as a prototypical example to illustrate various aspects of neural network representation of quantum many-body states. We first briefly review the classical neural networks, then we illustrate how to use neural networks to represent quantum states and density operators. Some physical properties of the neural network states, including entanglement features, representational power, and the relation with tensor network states, are discussed. For applications, we briefly review the progress of many-body calculating based on neural network states, neural network state approach to tomography, and also the classical simulation of quantum computing based on Boltzmann machine states. At the end of the work, some outlooks and open problems are given.