By Andy Choi
OKI has developed a quantum entangled light source, based on its proprietary technology. It is the first, unique light source to produce high-purity, entangled photon pairs that operate at room temperature.
A team of researchers led by Professor Shuichiro Inoue at Institute of Quantum Science, Nihon University, determined a signal-to-noise ratio that was 100 times better than optical fiber light sources. Using this light source, transmission tests were conducted with standard optical fibers. The quantum entangled photon-pairs were successfully transmitted over a distance of 140 km, representing the possibility of using next-generation quantum cryptography communication systems in the metropolitan area.
The team at Institute of Quantum Science, Nihon University developed a semiconductor-based single-photon detector that is capable of detecting photons with low noise and high efficiency at high repetition rates of 1 GHz. This detector evaluates the performance of the quantum entangled light source, where the generation of signal-to-noise ratio for the photon pairs is greater than that of conventional light source. Based on the newly developed quantum entangled light source and the single-photon detector, the possibility of quantum cryptography communications have been clearly demonstrated.
The various tests conducted on the transmission of quantum entangled photon pairs show that the quantum entanglement state can be efficiently maintained under long distance transmission up to 140 km over standard optical fibers. This performance contributes to excellent quantum cryptography communications over metropolitan area.
This new quantum entangled light source is being upgraded by OKI to achieve an efficient real-time quantum cryptography communications system.