Analyzing Common Electronic Structure Theory Algorithms for Distributed Quantum Computing

Abstract

To move towards the utility era of quantum computing, many corporations have posed distributed quantum computing (DQC) as a framework for scaling the current generation of devices for practical applications. One of these applications is quantum chemistry, also known as electronic structure theory, which has been poised as a “killer application” of quantum computing. To this end, we analyze five electronic structure methods, including the unitary coupled-cluster singles and doubles (UCCSD), unitary pair coupled-cluster doubles (UpCCD), unitary pair coupled-cluster with generalized singles and doubles (UpCCGSD), separable pair approximation plus generalized singles (SPA+GS), and local unitary cluster Jastrow (LUCJ) ansätze. The key benefit of these methods is that they can be found in common packages, such as Tequila and ffsim, that interface easily with the Qiskit Circuit Cutting addon. Herein, we highlight the challenges and aptitude of the aforementioned electronic structure methods for distribution using quasiprobability simulation with local operations (LO). The key findings of our work are that many of these algorithms cannot be efficiently parallelized using LO, and new methods must be developed to apply electronic structure theory within a DQC framework.