How to count one photon and get a(n average) result of 1000...

          @misc{ scivideos_PIRSA:16060034,
            doi = {10.48660/16060034},
            url = {https://pirsa.org/16060034},
            author = {Steinberg, Aephraim},
            keywords = {Quantum Foundations},
            language = {en},
            title = {How to count one photon and get a(n average) result of 1000...},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2016},
            month = {jun},
            note = {PIRSA:16060034 see, \url{https://scivideos.org/index.php/pirsa/16060034}}
          }
          

Abstract

I will present our recent experimental work using electromagnetically induced transparency in laser-cooled atoms to measure the nonlinear phase shift created by a single post-selected photon, and its enhancement through "weak-value amplification." Put simply, due to the striking effects of "post-selective" quantum measurements, a (very uncertain) measurement of photon number can yield an average value much larger than one, even when it is carried out on a single photon. I will say a few words about possible practical applications of this "weak value amplification" scheme, and their limitations. Time permitting, I will also describe other future and past work using "weak measurement," such as our studies quantifying the disturbance due to a measurement and what happens when it destroys interference; and our project to measure "where a particle has been" as it tunnels through a classically forbidden region – our prediction being that it will make it from one side of the barrier to the other without spending any significant time in the middle.