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Register a new userUltrabright narrow-band telecom two-photon source for long-distance quantum communication
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We demonstrate an ultrabright narrow-band two-photon source at the 1.5 -mu m telecom wavelength for long-distance quantum communication. By utilizing a bow-tie cavity, we obtain a cavity enhancement factor of $4.06times 10^4$. Our measurement of the second-order correlation function $G^{(2)} ({tau})$ reveals that the linewidth of $2.4$ MHz has been hitherto unachieved in the 1.5 -mu m 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 $3.94times 10^5$ pairs/(s$cdot$MHz$cdot$mW) is also the highest reported over all wavelengths.
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Heralded single photon source (HSPS) is an important way in generating genuine single photon, having advantages of experimental simplicity and versatility. However, HSPS intrinsically suffers from the trade-off between the heralded single photon rate and the single photon purity. To overcome this, one can apply multiplexing technology in different degrees of freedom to enhance the performance of HSPS. Here, by employing spectral multiplexing and active feed-forward spectral manipulating, we demonstrate a HSPS at 1.5 {mu}m telecom-band. Our experimental results show that the spectral multiplexing effectively erases the frequency correlation of pair source and significantly improves the heralded single photon rate while keeping the g{^(^2^)}(0) as low as 0.0006{pm}0.0001. The Hong-Ou-Mandel interference between the heralded single photons and photons from an independent weak coherent source indicates a high indistinguishability. Our results pave a way for scalable HSPS by spectral multiplexing towards deterministic single photon emission.
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