Norbert Riepl


A quantum hard to digest

I know I know nothing! This Socrates wisdom applies to most people when it comes to quantum technology. And yet, slowly but surely, we need to turn what we have researched into usefulness. This is what the OPENQKD consortium (Open European Quantum Key Distribution) has set itself the goal. 38 collaboration partners from all over the world want to advance the topic in extensive test environments.

The Bloch sphere is used in quantum mechanics to graphically represent states of qubits.

The Bloch sphere is used in quantum mechanics to graphically represent states of qubits.

A quantum of security

One of the best-known encryption methods, RSA (according to Rivest, Shamir, Adleman) has been used for decades to ensure the greatest possible security when transmitting data. Even high-performance computers would have taken a very long time to crack a 256-bit key. But in today's times this is put into perspective. The keys that cannot be cracked by the common user are approached with the Shor-algorithm and quantum computers, no longer the most secure safe. The door to the message could open in minutes. This is where QKD systems and "Post Quantum Cryptography" should help. The latter is needed above all to be able to include the 5G mobile phone network. This "ether" is too busy for the tiny photon. It is not possible to establish interference-free quantum channels. This is how critical telecommunications infrastructure is to be permanently secured. 

A quantum explanation

The goal of a key exchange is that two parties (in professional circles this is Alice and Bob) agree on a common secret key without a third party (Eve) receiving any information about it. Even if Eve "listens" to the communication channel. So what is it that makes QKD so interesting? The commonly known bit is either a "1" or a "0". It moves in real number space and has the two states mentioned above. No matter in which medium it is transmitted, it can be read out and sent to the receiver without change. A "man in the middle attack" would not be detectable. In contrast, a photon behaves like a Qbit, it can be both "0" and "1" at the same time. Meow! So Alice sends a Qbit to Bob. Eve intercepts the Qbit, reads it out and then sends the measured state to Bob. But Bob can now detect a change in the original Qbit. He registers a much higher error rate in the QKD protocol and can thus conclude an attack. So access to the key is not possible without physics revealing this flaw. 

A quantum of self-interest

In addition to the basic research for the consortium, the scientists also investigate various telecommunication-specific applications. This will help to answer the question to what extent a stable, safe and cost-saving operation of quantum optical communication links in the networks of Deutsche Telekom is possible. Last but not least, a target architecture for the QKD key exchange at a telecommunication provider has to be developed. For this purpose, the researchers in Berlin have an extensive fiber optic network with IT infrastructure at their disposal. All types of QKD systems can be tested on this network and limitations can be sounded out. At present, their range is limited to around 100 km, as no optical amplifiers can be used. The researchers are interested in how individual QKD systems can be interconnected to form an efficient QKD network. 

A quantum of cooperation

Different topics are dealt with at 16 locations throughout Europe. In Vienna, Madrid, Poznan and Berlin in larger test environments, which are intended to make the practical benefits more quickly accessible. Applications in the fields of health care, administration, banking, government, IT and telecommunications networks are being researched. The AIT Austrian Institute of Technology coordinates the research and consolidates the results with all partners. In this way, Europe is to be strengthened and brought to a leading position in the exploration of the use of quantum technology.

A Quantum of Solace ...

... I'd like to express my gratitude to those who didn't understand when things got too academically. This highly complex topic has also demanded a lot from me and I must thank above all our bright minds who immediately recognized and eliminated my mistakes. But stay tuned when it's "a quantum of information" again!

On topicMedia information: Deutsche Telekom builds test environment for quantum technology

The Bloch sphere is used in quantum mechanics to graphically represent states of qubits.

Deutsche Telekom builds test environment for quantum technology

Deutsche Telekom is researching how quantum optical networks can be interconnected and made secure.