In a study published in Science Advances, a research group led by Prof. ZHANG Wenfu from Xi’an Institute of Optics and Precision Mechanics(XIOPM) of the Chinese Academy of Sciences proposed a novel platform to overcome the challenges of aligning independent arrayed laser pairs in current Hong-Ou-Mandel (HOM) interference systems, which is of great significant for large-scale quantum communication.
As one of the most important characteristics of quantum optics, HOM interference with bunching effect has demonstrated tempting prospects in modern photonic quantum information processing. Although optical frequency combs can offer a useful scheme to resolve the challenge for massively parallel quantum communication by conventional wavelength division multiplexing (WDM) methods, the combs still confront with the difficulties in aligning independent soliton microcombs (SMCs).
In this study, researchers employed two independent on-chip SMCs to verify the feasibility of HOM interference with 50 comb-teeth pairs. In specific, two micro-ring resonators (MRRs) with identical parameters were responsible for the generation of SMCs. And the pump frequency and repetition rates were independently adjusted and locked to align optical frequencies.
Moreover, an erbium-doped fiber amplifier was employed to amplify the tapped pump laser and a periodically poled lithium niobate waveguide was adopted to achieve doubled frequency. The tests of the proposed microcombs showed that the beat frequency drifts and the average frequency fluctuation are only about 1.29 MHz and 0.912 MHz, respectively, indicating the negligible overlapping for HOM.
Experiment results of HOM interference demonstrated that the soliton existence range was over 3 GHz corresponding to the repetition rate tuning range over 100 kHz. And its average fringe visibility can reach up to 46%, indicating the potential of MRRs-based Kerr comb in large-scale quantum communication.
"This cost-effective approach is facilitated by the advancements in photonic integrated circuit technology, which allows for the creation of more efficient and scalable quantum communication systems,” said Prof. ZHANG Wenfu.
Principle of massively parallel channel HOM interference. (Image by XIOPM)
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