[quantum-info] Two theory seminars at IQC next week

[Ashwin Nayak]

Dear colleagues,

We have two theory seminars coming up next week, that may be of interest 
to you:

Monday, June 26, 2017, 2:30--3:30 pm, QNC 0101
Complexity of quantum impurity models
Sergey Bravyi, IBM TJ Watson

Tuesday, June 27, 2017, 2--3 pm, QNC 1201
Constraint Propagation Games
Zhengfeng Ji, University of Technology, Sydney

The abstracts are included below.

Best,
Ashwin
--

Monday, June 26, 2017, QNC 0101
Complexity of quantum impurity models
Sergey Bravyi, IBM TJ Watson

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




Tuesday, June 27, 2017, 2--3 pm, QNC 1201
Constraint Propagation Games
Zhengfeng Ji, University of Technology, Sydney

Constraint propagation games are simple extended nonlocal games that are
motivated by the propagation checking of quantum computation and have
found powerful applications in the study of quantum proof systems
recently. In this talk, we will introduce their definitions and basic
properties, demonstrate their uses in larger games as building blocks,
and illustrate the method that turns them into nonlocal games. Time
permitted, we will briefly discuss their advantage in establishing
rigidity properties and how they play a crucial role in showing that
quantum multi-prover interactive proof systems can be compressed to
nonlocal games with logarithmic message sizes.