Abstract: Modulator side channels threaten the security of quantum key distribution systems. Here, I first review a newly discovered modulator side channel for any practical bandwidth-limited modulator. After that, I present an overview of the recent development of the general theory and experiment on fully passive quantum key distribution, which removes modulator side channels completely by eliminating any modulators that carry secret information. Such a general theory is applied to different use cases: continuous variable, BB84, twin-field (TF), and measurement-device-independent (MDI)-QKD. Proof-of-principle experimental demonstrations are also discussed.
Bio: Hoi-Kwong Lo is a Professor of Physics and ECE (Electrical and Computer Engineering) at the U. of Toronto and a co-founder and CTO of Quantum Bridge Technologies, Inc. (“Quantum Bridge”). He was awarded a Ph.D. in Physics from Caltech in 1994. He has published over 100 papers. He is a Fellow of American Physical Society, an Optica Fellow and an IEEE Fellow with various awards including CAP-INO Medal for Outstanding Achievement in Applied Photonics (2022) and IEEE Photonics Society Quantum Electronics Award (2023).