| PhD Seminar

Name of the Speaker: Ms. Anagha Gayathri (EE20D031)
Guide: Dr. Anil Prabhakar
Venue: ESB-234 (Malaviya Hall)
Date/Time: 30th July 2025(Wednesday), 2 PM
Title: Plug and Play Twin Field Quantum Key Distribution

Abstract :

Quantum Key Distribution (QKD) enables secure communication by leveraging the principles of quantum mechanics, moving beyond the computational assumptions that underlie classical cryptographic systems. Measurement-Device-Independent QKD (MDI-QKD) enhances security by addressing detector-side vulnerabilities, while Twin-Field QKD (TF-QKD) further extends secure communication distances without the need for quantum repeaters.

In this work, we present the design and experimental realisation of a plug-and-play, three-time-bin-based TF-QKD system implemented using a Sagnac-based star-topology architecture. Self-compensation of phase and polarisation drifts is achieved through the Sagnac loop, enabling stable system operation under environmental fluctuations. We demonstrate secure key generation over a 50 km optical fibre link, achieving high interference visibility around 90% and a quantum bit error rate of 8%. We have also introduced a recirculating loop-based characterisation method for single-photon detectors and validated its performance against conventional techniques, highlighting its potential as a tool for detector evaluation.