SPOC DPTS Nature Communications 2016

First 2D Distributed-Phase-Reference QKD protocol (DPTS)

Friday 23 Dec 16


Davide Bacco
Assistant Professor
DTU Fotonik
+45 45 25 38 77


Leif Katsuo Oxenløwe
Professor, Group Leader
DTU Fotonik
+45 45 25 37 84


Karsten Rottwitt
Professor, Group Leader
DTU Fotonik
+45 45 25 63 84
In a recent publication in Scientific Reports, researchers from SPOC at DTU Photonics have introduced the first two-dimensional protocol for distributed-phase-reference quantum key distribution. The protocol offers a simple, practical, and fully integrable solution for achieving higher secret key rates in specific realistic network scenarios.

In a society based on the continuous exchange of sensitive data and information, the importance of secure and trustable information is essential. The classical encryption and decryption methods, will be no longer secure when a quantum computer becomes available, posing a serious threat to cryptosystems.


Quantum Key Distribution (QKD), a branch of quantum communications has opened a new era in the security of our information. Exploiting quantum physics, it is possible to share data in an unconditionally secure way, no longer based on mathematical assumptions, but founded on the basic principles of quantum mechanics. 

The quantum keys, combined with theOne Time Pad (OTP)encryption, permit an unconditionally secure data exchange between two or more remote parties.

Most of QKD protocols use a polarization encoding scheme, where the logical bits are encoded into the polarization state of photons. In case of the use of an optical fiber link, other degrees of freedom, like time, space and phase, since these are more robust in a long transmission link.

This work proposes a new type of QKD protocol, called DPTS, belonging to the distributed-phase reference family. In this protocol, the bit information is not more encoded into a single pulse, but by using the coherence between consecutive weak pulses, a secure quantum key can be extracted. Furthermore, the idea of combining two different degrees of freedom, like phase and time, forms the first two-dimensional distributed-phase protocol; robust to a noisy channel and less dependent on  device imperfections. By exploiting high-dimensional DPTS protocol, is possible to increase the channel capacity, and consequently the final secret key rate, that is the most important parameter a QKD system.

The next step is a real implementation of the protocol on a trial link and realization of an entire QKD system.


Davide Bacco, Jesper Bjerge Christensen, Mario A. Usuga Castaneda, Yunhong Ding, Søren Forchhammer, Karsten Rottwitt, and Leif Katsuo Oxenløwe


Link: http://www.nature.com/articles/srep36756

24 OCTOBER 2020