Calendar of Events
Colloquium - Quantum electrodynamics with a unity fine-structure constant and its applications to simulating the many-body physics of quantum impurity problems
Vladimir Manucharyan, University of Maryland
Quantum electrodynamics with a unity fine-structure constant and its applications to simulating the many-body physics of quantum impurity problems.
There are many reasons why we should be grateful to nature for setting the fine structure constant to alpha = 1/137.0. However, one can explore some intriguing consequences of light-matter coupling in the extreme case alpha ~ 1 using synthetic systems. We will describe the realization of such a system consisting of a single atom placed in a one-dimensional electromagnetic vacuum. The vacuum is a nearly insulating chain of Josephson tunnel junctions, which effectively acts as an on-chip telegraph transmission line with an exceptionally high wave-impedance. The atom is a properly designed superconducting qubit circuit terminating the line. The key manifestation of the alpha ~ 1 regime is that a single photon acquires a finite lifetime due to the decay into multiple lower-energy photons. Interestingly, calculating such an interaction-induced lifetime presents a significant challenge to theory. In fact, the observed many-body photon decay processes are fundamentally linked to the non-perturbative dynamics of quantum impurity problems. The two examples relevant for our experiment are the scattering of electrons on a spin-1/2 impurity (the Kondo model) or backscattering of electrons in a one-dimensional quantum wire (the boundary sine-Gordon model). Both models played a crucial role in developing theoretical tools to handle strongly-correlated phenomena. Thus, our experimental setup realizes an analog quantum computer for an important class of 1D many-body problems, and it can help benchmarking the computational methods of theoretical physics.