A Single-Photon Switch and Transistor based on Rydberg Blockade
Simon Baur
Abstract
This thesis reports the experimental realisation of a single-photon switch and transistor.To this end, Rydberg blockade in electromagnetically induced transparency (EIT) is used to create an interaction between two light pulses at the single photon level.In the experiment, a gate pulse containing one incoming photon on average is stored as a Rydberg excitation in an ultracold atomic gas using EIT.Subsequently a target light pulse is sent through the atomic ensemble.Without the gate pulse, the medium would be transparent due to EIT and the transmission would be high.If a gate excitation has been stored, however, Rydberg blockade suppresses the transmission of the target light pulse.The stored gate photon can be retrieved after the transmission of the target light.A retrieved photon heralds successful storage.In the corresponding postselected subensemble the transmission of the target light is reduced by an extinction factor of 0.05.This reduction is robust if the number of incoming gate photons or target photons is varied.In a conceptually improved version of the experiment, a single-photon transistor is realised that shows a gain above unity.The gain quantifies the change in the transmitted target photon number per incoming gate photon.For one incoming gate photon on average, a gain of 20 is observed.The improved experiment uses a Förster resonance, the benefit of which becomes directly evident in an improved gain and extinction.If a Rydberg excitation is created during the gate pulse, then the transmission of the target light pulse drops substantially.By setting a discrimination threshold for the number of detected target photons, it is possible to detect in a single shot with a fidelity of 86% whether a Rydberg excitation was created during the gate pulse.Since the gate excitation is not retrieved by the target light, this detection method is nondestructive.i iii 6.2.Experimental Sequence . . . . . . .