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French Researchers Suggest “Continuous Variable” QKD Could Be Made Absolutely Secure

By IQT News posted 27 Jun 2019

(Physics.aps.org) Anthony Leverrier at Inria in France and colleagues have provided theoretical arguments for the security of continuous-variable (CV) QKD, a version that relies on interferometric detection schemes widely used in high-speed telecom networks. The result suggests that CVQKD holds potential for large-scale deployment in such networks.
Most protocols for quantum key distribution (QKD)—a quantum cryptography technique—encode an encryption key in discrete quantum states, such as the two orthogonal polarizations of a photon. Instead of discrete polarization states, CVQKD uses coherent quantum states that can be encoded in continuous variables like the amplitude and phase of an optical signal traveling through a fiber.
Leverrier and his team analyzed a CVQKD protocol that uses only four quantum states, which can be reliably prepared with available optical technology. Their analysis shows that this protocol could securely transmit a secret key over distances ranging from 50 to 150 km, depending on the noise in the transmission channel.

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