Quantum communication is based on the exchange of entangled quantum states and enables secure data transmission over both short and long distances of up to several hundred kilometers. This technology is becoming increasingly important, especially with the development of powerful quantum computers which could potentially compromise conventional encryption methods. To protect future communication systems from such threats, scientists are researching tap-proof quantum keys based on the principles of quantum mechanics.

The team of Prof. Marquardt, who also holds the chair for “Optical Quantum Technologies” at the Friedrich-Alexander Universität Erlangen-Nürnberg, is investigating methods for the reliable distribution of quantum keys (Quantum Key Distribution, QKD) between sender and receiver. “What is really interesting is that we are actually using a laser, something that is used very often. But we modulate the laser very, very little, actually in the quantum range. That’s enough to exchange such quantum keys,” explains Prof. Marquardt.

The security of quantum keys is based on fundamental quantum mechanical principles: measurement induced distortions and the no-cloning theorem prevent undetected manipulation. Quantum states are exchanged between two different receivers, which can determine whether external interference – i.e. an eavesdropping attempt – has taken place by measuring certain quantum properties. Any access by a third party inevitably leads to measurable disturbances in the quantum state, since unknown quantum states can neither be copied exactly nor measured without disturbance. These disturbances manifest themselves as errors in the transmission and signal possible eavesdropping.

Research in quantum communication is therefore a significant step towards the development of future tap-proof communication networks, resistant even to attacks by powerful quantum computers.

The full report is available here in the media centre.