CoQuS-Talk by Aephraim Steinberg; University of Toronto

08.10.2018 17:00 - 19:00

on "Counting photons as they fly and timing atoms as they tunnel"

The Vienna Doctoral Programme on Complex Quantum Systems invites you to a


Seminar Talk



Aephraim Steinberg

Dept of Physics and Centre for Quantum Information & Quantum Control

University of Toronto     


Counting photons as they fly and timing atoms as they tunnel

How much can one photon affect another?  How long does a particle spend in the forbidden region of a tunnel barrier?  These longstanding questions are of both fundamental and potentially practical importance.  I will present two experiments in which we used ultracold atoms to address them.


In the first, we used an atomic coherence effect to generate such strong photon-photon interactions that we could measure the nonlinear optical phase imprinted on a probe beam by a separate, single-photon-level, pulse.  We also found that when the right post-selection is performed on this latter photon, it can “act like” many more than 1 photon, writing a larger phase shift, in accordance with the surprising predictions of the “weak measurement” formalism of Yakir Aharonov et al.  Most recently, we have started to use Rydberg atoms to generate even larger interactions.  I will say a few words about the philosophical implications of this “weak value amplification” result.

In the second, we are measuring the traversal time for ultracold (~900 pK) atoms traversing an isolated tunnel barrier, and preliminary results confirm our predictions that particles traverse a barrier faster when they have to tunnel through it than when they have enough energy to travel over it.  I will place this in the context of the century-old debate over how long tunneling takes.


Monday, 8 October 2018,

16:30h get-together with coffee and snacks!


Lise Meitner Hörsaal, Strudlhofgasse 4, 1st floor, Vienna


The seminar talk will be preceded by a CoQuS Student talk at 17:00h by

Lorenzo Magrini

University of Vienna

Nanophotonic near-field levitated optomechanics
by: Markus Aspelmeyer

Lise Meitner Hörsaal, Strudlhofgasse 4, 1st floor, Vienna