Quantum Correlations for Secret Key Distribution

Quantum mechanics allows secure communication against eavesdropping. The security relies on fundamental laws of physics and, therefore, it cannot be broken by any advance in computational power of potential adversaries. The reason for this is that any att empt to eavesdrop on the signals will have a quantum mechanical back-reaction on the signals that will change them on average. This change manifests itself in certain occurrence of errors of the signal transmission. In real implementations, however, such errors will occur also because of technical problems in the realization, e.g. channel and detection noise. Still, it is possible to regain the security against eavesdropping by adding auxiliary classical communication protocols that correct the errors an d that allow decoupling an eavesdropper from the secret information. The security claim can in this way be restored without any residual security loopholes. However, there are limitations about how much noise can be tolerated in these implementations. Th ese limitations translate in upper bounds on transmission distance and transmission rate. It is an active topic of research to push these limits as far out as possible. In this research project we will contribute to the ongoing research. We start with a specific observation that has been published recently. Based on this, we will exploit the underlying idea to generate new auxiliary classical communication protocols, involving new steps in combination with known and explored tools. The result of this re search will be an increased application range of quantum secured communication.