Colloquium: Sergey Bravyi

Monday, June 26, 2017 2:30 pm - 2:30 pm EDT (GMT -04:00)

Complexity of quantum impurity models

Sergey Bravyi, IBM Research

I will discuss classical and quantum algorithms for simulation of quantum impurity models. Such models describe a bath of free fermions coupled to a small interacting subsystem called an impurity. Hamiltonians of this form were famously studied by Anderson, Kondo, Wilson and others in 1960s.

More recently, impurity models found applications in DMFT simulations of strongly correlated fermionic systems. In this talk I will show that under very mild technical conditions ground states of impurity models can be efficiently prepared on a quantum computer. I will also describe a classical algorithm for approximating the ground energy of impurity models. The running time of our algorithm is polynomial in the system size and quasi-polynomial in the inverse approximation error. To arrive at these results we prove a general theorem characterizing correlations in the ground states of impurity models.

Based on a joint work with David Gosset