Tobias Gehring

Project title

Quantum cryptography with squeezed light for telecom networks

What is your project about?

The security of the internet is threatened by quantum computers which will be able to decipher today's encrypted messages within a short period of time. When classified data from security critical infrastructure, from the government or military, from banks or companies can fall into the wrong hands, the dangerous consequences for our society would be devastating. Quantum key distribution (QKD) offers a solution based on properties of quantum mechanics. In QKD two parties exchange quantum states of light to distribute a key which can be mathematically proven to be only known by them and nobody else. Any eavesdropping on the fiber cable used for sending light between the two parties can be detected. To enable widespread deployment of QKD in telecom networks the QKD signal has to be multiplexed with telecommunication signals for data transmission. However, powerful telecommunication signals produce noise which cannot be destinguished from an attacking eavesdropper. The amount of acceptable noise level in QKD systems today is not sufficient for integration into the existing telecom infrastructure. In this project I will develop a new technique for QKD using so-called squeezed quantum states, which increases the noise tolerance dramatically and will make telecom network integration possible. The new technique will furthermore reduce the power consumption of the system.

How did you become interested in your particular field of research?

During my undergraduates in Physics I did an internship at a German company selling optical vibration sensors. There I learned that quantum optics has means to improve the sensitivity of optical sensors. I continued this route and explored the generation of squeezed quantum states and their application in sensors. I discovered the related field of quantum cryptography in which I then did my PhD and got hooked because it combined my interests not only in quantum optics but also in computer science.

What are the scientific challenges and perspectives in your project?

Using squeezed states for quantum cryptography requires scientific progress in several research fields: quantum optics (quantum state generation and detection), theoretical quantum information (security proofs) and computer science (error correction codes). Attempts to integrate quantum cryptography into telecommunication networks are rather new and squeezed light has not yet been tested outside of lab environments. It will be exciting to see the challenges ahead of us when field testing quantum technology.

What is your estimate of the impact, which your project may have to society in the long term?

Data security is of utmost importance to society. Our digitilized world would not work without it. In contrast to conventional cryptography used at the moment it is not possible to break security of quantum cryptography with quantum computers. Quantum cryptography is therefore an essential tool in the future toolbox for data encryption. My project will help to make quantum cryptography ready for integration of quantum cryptography into existing infrastructure.

Which impact do you expect the Sapere Aude programme will have on your career as a researcher?

The Sapere Aude starting grant allows me to strengthen my research in quantum cryptography and to pursue new ideas. It has a significant impact as it will allow me to consolidate and expand my research team and it will strengthen my international network.

Background and personal life

I am originally from Germany and moved to Denmark in 2013. I have two kids (4 and 6) which I enjoy very much. I love making things work with the newest available technology and dedicated solutions perfectly tailored to a problem. In my free time I go roller skating.