Research Progress

NTSC Researchers Developed All-fiber Telecom Band Energy-time Entangled Biphoton Source

Author:XIONG Tiantian; LIU Yuting       ArticleSource:       Update time:2023/05/11

Recently, a research group led by Prof.ZHANG Shougang and Prof. DONG Ruifang from the National Time Service Center(NTSC) of the Chinese Academy of Sciences (CAS) developed a device for All-fiber telecom band energy-time entangled biphoton source. The research is published in Chinese Optics Letters and has been selected as Editor' pick.

Quantum entangled photon source is an important resource in quantum optical system and plays an indispensable role in the development of quantum information technology. Energy-time entanglement has attracted growing attention due to its strong temporal correlation and robustness to loss and decoherence when propagating through long-distance fiber links, and energy-time entangled biphoton source at the telecom bands has been applied as the resource in numerous fiber-based quantum communication and metrology experiments. The energy-time entangled photon source with high compactness and high stable performance instrument is crucial for extending quantum information technologies from proof-of-principle demonstration to realistic applications over long-haul field fiber links or networks.

Benefiting from the advantages of compact and lightweight designs, simple production, and high stability, the entangled source developed by researchers will provide a convenient and valuable resource for various field turnkey quantum communication and metrology applications. The research group integrated all the physical elements into a cabinet of 12-liter and reducing weight to 5kg by using an all-fiber structure and photo-electric integration design. At a pump power of 800 μW, the generated photon pairs reach a rate as high as 6.9 MHz with the coincidence-to-accidental ratio (CAR) better than 1150. By measuring the long-term performances of Hong–Ou–Mandel (HOM) interference visibility and CAR at a pump power of 60 μW, the stability of the biphoton source has also been tested. Within 10 h of continuous operation, the directly measured HOM visibility without any noise subtracting maintains at 91.8 ± 0.8%, and the CAR is consistently at the level of 10,528.8 ± 604.2.

"Such an all-fiber biphoton source has already been successfully applied in their quantum clock synchronization experiments over 100 km urban fiber links, quantum nonlocality test and quantum microwave photonics research," said Prof. Dong.

Fig. 1 (a) Schematic diagram and (b) Physical image of the all-fiber telecom-band energy-time entangled biphoton source. Measurement results of (c) the CAR and photon pair generation rate as a function of the pump power, (d) the Hong–Ou–Mandel (HOM) interference visibility in the period of more than 10 h at the pump power of 60 μW.

XIONG Tiantian
National Time Service Center, Chinese Academy of Sciences