Long-distance quantum communication is possible over a 600-kilometer fiber link.
With its new statement, Toshiba announced that it will take some important steps on the way to the quantum internet, and with a new technique, fiber optic transmission of more than 600 km has been achieved. In addition, information was encoded with quantum cryptography for ultimate data privacy protection.
The data was transported and stored in various locations covering a total travel distance of approximately 600 km via fiber optic cables. For this, a new double band stabilization technique called Twin Field, which is a first in the world, was used. This technique helped circumvent the problem of temperature and voltage fluctuations often found in quantum communication.
As data flows across optical cables, highly sensitive qubits used to encode and transmit information can become unstable if care is not taken. It can also cause errors in the data.
Toshiba’s dual-band technique sends two optical reference signals at different wavelengths to minimize phase fluctuations over long distances. The first wavelength is used to cancel rapidly changing fluctuations, while the second is used for fine-tuning the phase. The transmitted data is repeatedly verified at various stages of its journey across the network, and no signs of degradation have been observed due to the new technique.
Dual band stabilization will be used primarily for long-range Quantum Key Distribution (QKD). Commercial QKD systems are limited to around 100-200 km of fiber. Toshiba’s Twin Field QKD protocol was applied to fiber connections and a distance of 600 km was seen for the first time in QKD.
QKD allows users to securely transfer confidential information (such as bank statements, health records, private calls) over an untrusted communication channel (such as the Internet). In other words, it is a very critical development for governments and some organizations, if not for us end consumers.