Imagine a communication network that is impervious to eavesdropping. This is the promise of quantum communications. By leveraging the principles of quantum mechanics, any attempt to intercept transmitted qubits will inevitably alter their state, leading to immediate detection of the eavesdropping.
Chinese researchers at Tsinghua University have achieved a significant scientific breakthrough in quantum communications. They have accomplished, for the first time, secure and direct data transmission at a speed of 2.38 kilobits per second over optical fibers spanning a distance of 104.8 kilometers. This is a record-breaking achievement, far surpassing the team’s previous record from 2022, which was 0.54 bits per second over a distance of 100 kilometers using the Quantum Secure Direct Communication (QSDC) protocol.
The team developed an enhanced version of the QSDC protocol, named quasi-QSDC, designed to overcome the limitations of its predecessor. The original QSDC protocol relied on bidirectional photon exchange between the sender and receiver for transferring quantum states, resulting in information loss and constrained communication performance. The new protocol, however, is unidirectional and utilizes single photons, transmitting data in one direction using a single photon to represent the quantum state.
The protocol was also tested over shorter distances, achieving higher speeds of 4.08 kilobits per second at 50 kilometers, approaching the speeds of dial-up internet in the 1990s. These speeds are considered adequate for transmitting text, image, and audio files.
The research team is confident that they will soon be able to double or more the data transfer speed and extend the transmission distance to 150 kilometers or beyond.
This protocol paves the way for the development of a global secure communication network (a quantum internet) that relies on the transfer of quantum states, or qubits, instead of the bits used in current communications, enabling the detection of all eavesdropping and network intrusion attempts.
The researchers published their achievement in the journal Science Advances on February 21st.
