Quantum key distribution with classical Bob
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Updated: Jul 11, 2026

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
Published on: May 30, 2014
Michel Boyer1, Dan Kenigsberg, Tal Mor
1Département IRO, Université de Montréal, Montréal (Québec), Canada.
Abstract:
Secure key distribution among two remote parties is impossible when both are classical, unless some unproven computation-complexity assumptions are made, such as the difficulty of factorizing large numbers. On the other hand, a secure key distribution is possible when both parties are quantum. What is possible when only one party (Alice) is quantum, yet the other (Bob) has only classical capabilities? We present a protocol with this constraint and prove its robustness against attacks: we prove that any attempt of an adversary to obtain information necessarily induces some errors that the legitimate users could notice.
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