Quantum computing from a disordered-systems perspective (Groupe de travail Quantique) 
			 Chris Baldwin
				University of Maryland
			
			Mardi 04/04/2023, 11:00-12:00
			Salle Claude Itzykson, Bât. 774, Orme des Merisiers
			Quenched disorder, in the sense of random imperfections in a system, is 
both a blessing and a curse for scientists — it can give rise to a host 
of novel phenomena, but it also tends to impede transport and 
communication. Here we cover examples of both from our work on quantum 
dynamics, motivated primarily by proposals for quantum computing and 
quantum information protocols.
In the first part, we discuss tunneling processes in “rugged energy 
landscapes”, of which the classic optimization problems from computer 
science (such as Traveling Salesman and Satisfiability) are examples. 
After describing how many such problems share essential features with 
mean-field spin glasses — long-range interactions, disorder, frustration 
— we summarize our understanding of the quantum dynamical phases in the 
latter.
In the second part, we consider the opposite extreme of 1D 
nearest-neighbor spin chains. We describe how “Lieb-Robinson bounds” 
have proven to be an invaluable tool for studying both many-body 
dynamics and constraints on quantum information protocols. We then cover 
our recent work developing Lieb-Robinson bounds tailored to disordered 
spin chains.