Quantum Communication


Research Unit D: Quantum Communication

Communication is at the heart of our daily life. Enor­mous progress has been achieved in recent years in modern telecom technologies that are now ca­pable of literally providing information at our fin­gertips, at virtually any place on earth. Quantum information methods can improve and extend the capabilities of state-of-the-art communication sys­tems – but the user cannot be expected to care about quantum physics. Significant improvements and technological developments are required to provide seamless integration of quantum com­munication methods to make their application fully transparent for the everyday user.


The security and confidentiality of information transfer are threatened. A future, large-scale quan­tum computer will break the most widely used encryption systems and already now security agencies worldwide advise to search for so-called post quantum security systems.

Quantum key distribu­tion employs quantum states of light and is the only solution known today which will withstand the attack of any quantum computer. Even better, it is the only method for which the user can quantify the security of the key distribution, i.e. measure the knowledge the eavesdropper can possess about the key. For the first time in secure communication, the communicating par­ties do not have to rely on the inabilities of the attacker.

First commercial systems are available but significant improve­ments are required to enable secure com­munication to a widespread community. Crucial issues here are the usability and reliability of the quantum key exchange devices, and of course also the possibility to communicate securely over long dis­tances. Trusted node network components for quantum key distribution have to be developed and integrated together with industrial partners into standard network components.

The current develop­ment of optical communication to satellites offers the unique opportunity to add quantum security to these systems from an early stage on, thereby enabling secure communication on a global scale. Conversely, the technological advance of space-proven quantum communication components will foster the development of highly robust real-world solutions for quantum communication and their integration with conventional communication systems.

Extending today’s communication network structure into the quantum domain will bring the ultimate solution enabling full quantum communication possibilities - the often-referred-to quantum internet. In addition to point-to-point quantum key distribution, the quantum internet will be able to distribute quantum states between the quantum memories of functional quantum processors. It will thus pro­vide unconditional communication security and will enhance quantum computing and quantum sim­ulation capabilities. The main challenge arising in the realization of such a quantum network con­cerns the efficient, high-fidelity transfer of quantum states over large distances, over noisy and lousy communication channels, and to a network of many users. The quantum repeater network is the answer to these challenges. So far, first demonstrations of basic functionalities of quantum repeater components have been achieved. However, a series of crucial developments, ranging from sources of quantum states of light to quantum interfaces between stationary and flying quantum bits to net­work-compatible photonic quantum gates are still required in order to go beyond these first steps and to realize scalable solutions for quantum networks.

RU-D Coordinators

Harald Weinfurter

Experimental Quantum Physics

Group Webpage

Gerhard Rempe

Quantum Dynamics

Group Webpage

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