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EncryptionPolarization modulationQKDQuantum key distributionSecure communication


This patent describes a method and apparatus for the high speed modulation of the polarization of photonic impulses, for the purpose of Quantum Key Distribution (QKD) creation. This method improves the encryption of secret keys that allow secure communication between key holders.

Technical features

Quantum key distribution (QKD) is an emerging quantum technology that uses the quantum mechanic properties of light to create a secret encryption key that can be shared by two sides. Several implementations of QKD systems have been developed in recent years that exploit photonic degrees of freedom, such as polarization, time-bin, and orbital angular momentum, in free-space, optical fiber, or even satellite links.

These patented cryptographic keys can be exploited to communicate encrypted messages using secure cryptographic algorithms.  This technology is completely automated in generating perfectly known polarization states that do not vary over time. It also offers the possibility to change configuration (polarization or time-bin coding) automatically. Finally, it includes a polarization maintenance fibre at the input for greater stability.

A prototype of the modulator has already been tested within the University network. Current TRL is 6 but it will increase thanks to further trials on other public networks that will optimize the technology.

Possible Applications

  • Communication security for government, military, civil and academic applications.


  • Completely automated apparatus;
  • Generates perfectly known and invariable polarization states;
  • Automatic configuration change (polarization or time-bin coding);
  • Great stability;
  • Quantum Bit error Rate < 0,1%;
  • Low power, simple driving system.