Researchers resolve a long-standing challenge in quantum optics: optimal
Bell-state measurement of time-bin encoded qubits, to enhance the key rate
of secure quantum communication.
Integrated quantum photonics (IQP) is a promising platform for realizing
scalable and practical quantum information processing. Up to now, most of
the demonstrations with IQP focus on improving the stability, quality, and
complexity of experiments for traditional platforms based on bulk and fiber
optical elements. A more demanding question is: “Are there experiments
possible with IQP that are impossible with traditional technology?”
This question is answered affirmatively by a team led jointly by Xiao-Song
Ma and Labao Zhang from Nanjing University, and Xinlun Cai from Sun Yat-sen
University, China. As reported in Advanced Photonics, the team realizes
quantum communication using a chip based on silicon photonics with a
superconducting nanowire single-photon detector (SNSPD). The excellent
performance of this chip allows them to realize optimal time-bin Bell state
measurement and to significantly enhance the key rate in quantum
communication.
The single photon detector is a key element for quantum key distribution
(QKD) and highly desirable for photonic chip integration to realize
practical and scalable quantum networks. By harnessing the unique high-speed
feature of the optical waveguide-integrated SNSPD, the dead time of
single-photon detection is reduced by more than an order of magnitude
compared to the traditional normal-incidence SNSPD. This in turn allows the
team to resolve one of the long-standing challenges in quantum optics:
optimal Bell-state measurement of time-bin encoded qubits.
This advance is important not only to the field of quantum optics from a
fundamental perspective, but also to quantum communications from the
application perspective. The team employs the unique advantages of the
heterogeneously integrated, superconducting silicon-photonic platform to
realize a server for measurement-device-independent quantum key distribution
(MDI-QKD). This effectively removes all possible detector side-channel
attacks and thus significantly enhances the security of quantum
cryptography. Combined with a time multiplex technique, the method obtains
an order-of-magnitude increase in MDI-QKD key rate.
By harnessing the advantages of this heterogeneously integrated system, the
team obtains a high secure key rate with a 125 MHz clock rate, which is
comparable to the state-of-the-art MDI-QKD experimental results with GHz
clock rate. “In contrast with GHz clock rate MDI-QKD experiments, our system
doesn’t require a complicated injection locking technique, which
significantly reduces the complexity of the transmitter,” says Xiaodong
Zheng, a PhD student in Ma’s group and first author of the Advanced
Photonics paper.
“This work shows that integrated quantum-photonic chips provide not only a
route to miniaturization, but also significantly enhance the system
performance compared to traditional platforms. Combined with integrated QKD
transmitters, a fully chip-based, scalable, and high-key-rate metropolitan
quantum network should be realized in the near future,” says Ma.
Reference:
Heterogeneously integrated, superconducting silicon-photonic platform for
measurement-device-independent quantum key distribution” by Xiaodong Zheng,
Peiyu Zhang, Renyou Ge, Liangliang Lu, Guanglong He, Qi Chen, Fangchao Qu,
LaBao Zhang, Xinlun Cai, Yanqing Lu, Shining N. Zhu, Peiheng Wu, Xiaosong
Ma, 30 October 2021, Advanced Photonics.
DOI: 10.1117/1.AP.3.5.055002
Tags:
Physics