Seminar: A/Prof Dominic Berry, Macquarie University

Presenter: A/Prof Dominic Berry, Macquarie University

Title: Accelerated quantum algorithms for electronic structure

Abstract:  Simulating the electronic structure of molecules or materials is one of the most important practical applications of quantum computers.  Of particular interest is FeMoco, which cannot be simulated classically and is of great interest due to its role in nitrogen fixing.  Early estimates of the complexity of the quantum simulation indicated that 10^14 T gates would be needed, which would not be feasible due to the magic-state distillation overhead in an error-corrected quantum computer. 

In this talk I present alternative approaches that greatly reduce the complexity.  First, by using a plane-wave basis we can provide scaling as N^{1/3} in the number of orbitals, which is a vast improvement over N^10 scaling in early algorithms.  Second, using a low-rank tensor factorisation we can provide N^{3/2} scaling even for the Gaussian orbitals that are useful for molecules.  Third, by taking advantage of sparsity together with using a more advanced version of QROM, we can provide an algorithm that uses only about 84 billion Toffoli gates for FeMoco, about three orders of magnitude improvement.

Hosted by: UTS Centre for Quantum Software and Information (QSI)