Modulation leakage vulnerability in continuous-variable quantum key distribution

Nitin Jain*, Ivan Derkach, Hou Man Chin, Radim Filip, Ulrik L. Andersen, Vladyslav C. Usenko, Tobias Gehring

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Flaws in the process of modulation, or encoding of key bits in the quadratures of the electromagnetic light field, can make continuous-variable quantum key distribution systems susceptible to leakage of secret information. Here, we report such a modulation leakage vulnerability in a system that uses an optical in-phase and quadrature modulator to implement a single sideband encoding scheme. The leakage arises from the limited suppression of a quantum-information-carrying sideband during modulation. Based on the results from a proof-of-concept experiment, we theoretically analyze the impact of this vulnerability and show that the leakage reduces the range over which secret key can be obtained, and can even lead to a security breach, if disregarded. We also study the efficacy of additional trusted noise to counter this vulnerability.

Original languageEnglish
Article number045001
JournalQuantum Science and Technology
Issue number4
Number of pages12
Publication statusPublished - Oct 2021

Bibliographical note

Publisher Copyright:
© 2021 IOP Publishing Ltd.


  • Continuous variables
  • Quadrature
  • Quantum cryptography
  • Quantum hacking
  • Quantum key distribution
  • Sideband


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