# Condensed Matter Seminar "Universal photonic quantum computation via time-delayed feedback"

#### Monday, May 7, 2018 - 11:30am

Speaker(s):

Hannes Pichler (Harvard University)

We propose and analyze a deterministic protocol to generate two-dimensionally entangled photonic states using a single quantum emitter coupled to a 1D waveguide. I will show that delayed quantum feedback dramatically expands the class of achievable quantum states in such settings and in particular allows to generate universal resources for measurement based quantum computation. As a physical implementation, we consider a nanophotonic setting where delayed feedback is introduced by terminating the waveguide on one side with a mirror. We identify the class of many-body quantum states that can be produced using this approach, characterize them in terms of 2D tensor network states and give an explicit protocol to generate the 2D cluster state.