Francesco Evangelista / Emory University
Buehler 415
3:30 pm
Solving the electronic many-body Schrödinger equation for strongly correlated systems is a significant challenge in physics, materials science, and chemistry. Classical numerical simulations of these systems are severely limited by the exponential scaling of the many-body basis. Quantum computers can efficiently represent and manipulate quantum states, and therefore, could potentially enable an exponential speedup in the simulation of many-body problems. Recent advances in the engineering quantum hardware have played a critical role in reinvigorating interest in the development of quantum simulation algorithms. Recent work has centered on the development of quantum phase estimation and the variational quantum eigensolver (VQE) algorithms. These two techniques have been successfully applied to solve small molecular problems, both using quantum simulators and real hardware. Of the two, however, VQE is seen as the most promising for near-term noisy quantum computers. In the first part of this talk, I will consider various unitary coupled-cluster (UCC) ansätze that are commonly used in VQE. In particular, I will focus on identifying which forms of UCC can represent any quantum state. From these exact UCC ansätze, it is possible to construct a quantum computing-friendly representation of a quantum state that employs an infinite sequence of particle-hole or general one- and two-body substitution operators. In the second part of this talk, I will discuss quantum algorithms that are analogous to Krylov subspace methods. I will consider a multireference selected quantum Krylov (MRSQK) approach. This method uses quantum measurement to identify a set of important zeroth-order states, from which we generate a set of Krylov sequences using the real-time propagator. The MRSQK method is tested on several molecular systems that display strong correlation effects and compared to classical selected configuration interaction and an adaptive VQE approach.
I was born in the beautiful city of Vasto in the Abruzzo region of Italy. I did my bachelor studies at the Scuola Normale Superiore in Pisa, Italy and my Ph.D. with Prof. Henry Schaefer at the University of Georgia (2003). After graduating, I did a postdoc in Mainz, Germany as an Alexander von Humboldt Junior Fellow and then moved to Yale for a second postdoc with Prof. John Tully. I joined the Chemistry Department at Emory University as an assistant professor in 2013 and was promoted to associate professor in 2019.