Ultrabright narrow-band telecom two-photon source for long-distance quantum communication
Kazuya Niizeki, Kohei Ikeda, Ming-Yang Zheng, Xiu-Ping Xie, Kotaro Okamura, Nobuyuki Takei, Naoto Namekata, Shuichiro Inoue, Hideo Kosaka, Tomoyuki Horikiri · Applied Physics Express · 2018
We demonstrate an ultrabright narrow-band two-photon source at the 1.5 µm telecom wavelength for long-distance quantum communication. By utilizing a bow-tie cavity, we obtain a cavity enhancement factor of 4.06 × 10 4 . Our measurement of the second-order correlation function G (2) (τ) reveals that the linewidth of 2.4 MHz has been hitherto unachieved in the 1.5 µm telecom band. This two-photon source is useful for obtaining a high absorption probability close to unity by quantum memories set inside quantum repeater nodes. Furthermore, to the best of our knowledge, the observed spectral brightness of 3.94 × 10 5 pairs/(s·MHz·mW) is also the highest reported over all wavelengths.