Optical Quantum Manipulations and Applications Based on Electromagnetically Induced Transparency

Abstract

Photons are suitable carriers in quantum information technologies because of their fast propagation speed and weak interaction with the environment The manipulation of the quantum states of individual photons is hence an essential however a challenging task in quantum information technologies because of the fragility of the quantum states To date various issues for optical-quantum manipulation have been proposed in a variety of schemes Among them electromagnetically induced transparency (EIT) paves a potential way in manipulation of photons Owing to the resonant process EIT largely increases the interaction strength and allows the narrowband interaction In this dissertation we focus on several tasks in quantum information science and propose the schemes based on EIT in the medium of the cold atomic ensemble In the first work we propose an all-optical cross-phase modulation scheme based on EIT In the experiment we have observed the pi phase shift of one light pulse induced by the other with both containing eight photons in each pulse According to the theoretical model it is possible to reach the goal of $pi$ phase modulation per photon if one can prepare two phase-coherent single-photon pulses In the second work we demonstrate an efficient frequency conversion scheme using resonant four-wave mixing (FWM) based on EIT by arranging the applied laser beams in a backward configuration both theoretically and experimentally In the experiment we observe 63% conversion efficiency (CE) with optical depth (OD) of 48 under the phase-mismatch value of 0 273pi Moreover we show that the phase mismatch can be compensated by the two-photon-detuning induced phase shift in EIT and we observe the CE of 76 % using an optical depth (OD) of 52 after compensation To our knowledge this is not only the first time ever that observes the CE exceeding 25% in resonant the FWM but also the highest record of CE under the resonant condition Moreover we also demonstrate that the scheme is indeed a quantum frequency conversion process if the CE reaches 100% and discuss the generation of the narrowband bi-photon source based on EIT using the fully-quantum approach in the last work According to the model it is possible to generate the paired photons with kHz-order bandwidth if the dephasing rate of a system is small enough

Date of Award	2020
Original language	English
Supervisor	Yong-Fan Chen (Supervisor)