Speaker: Dr. Ravikumar Chinnarasu, National Tsing Hua University

Place: Room 124, Physics Department, NTHU

TIme: 1:20PM, 3/15, 2021

Title: Efficient generation of subnatural-linewidth biphotons by controlled quantum 
interference 

Abstract:
Biphotons of narrow bandwidth and long temporal length play a crucial role in 
long-distance quantum communication (LDQC) and linear optical quantum computing 
(LOQC). However, generation of these photons usually requires atomic ensembles with 
high optical depth or spontaneous parametric down-conversion with sophisticated 
optical cavity. By manipulating the two-component biphoton wave function generated 
from a low-optical-depth (low-OD) atomic ensemble, we demonstrate biphotons with 
subnatural linewidth in the sub-MHz regime. The potential to shape and manipulate 
the quantum wave packets of these temporally long photons is also demonstrated and 
discussed. Our work has potential applications in realizing quantum repeaters and 
large cluster states for LDQC and LOQC, respectively. The possibility to generate 
and manipulate subnatural-linewidth biphotons with low OD also opens up the 
opportunity to miniaturize the biphoton source for implementing quantum technologies 
on chip-scale quantum devices.