Quantum Communications - Dual band stabilization

https://www.zdnet.com/article/researchers-created-an-un-hackable-quantum-network-over-hundreds-of-kilometers-using-optical-fiber/ 

Excerpt:

To tackle the instable conditions inside optical fibers, Toshiba's researchers developed a new technique called "dual band stabilization". The method sends two signals down the optical fiber at different wavelengths. The first wavelength is used to cancel out rapidly varying fluctuations, while the second wavelength, which is at the same wavelength as the qubits, is used for finer adjustments of the phase. 

Put simply, the two wavelengths combine to cancel environmental fluctuations inside the fiber in real time, which according to Toshiba's researchers, enabled qubits to travel safely over 600 kilometers. 

Already, the company's team has used the technology to trial one of the most well-known applications of quantum networks: quantum-based encryption. 

Known as Quantum Key Distribution (QKD), the protocol leverages quantum networks to create security keys that are impossible to hack, meaning that users can securely exchange confidential information, like bank statements or health records, over an untrusted communication channel such as the internet.