Silicon Photonic Chip Boosts Quantum Security

Researchers from Nanjing University and Sun Yat-sen University developed a quantum communications platform based on a silicon photonic chip with a superconducting nanowire single-photon detector (SNSPD). The chip’s performance enabled the team to realize optimal time-bin Bell-state measurement, and to significantly enhance the key rate in quantum communication.

By harnessing the unique high-speed property 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 therefore allowed the team to resolve one of the long-standing challenges in quantum optics: optimal Bell-state measurement of time-bin encoded qubits.

The advancement is important not just for quantum optics, but also for quantum communications, from an applications perspective. The team employed the advantages of the heterogeneously integrated, superconducting silicon-photonic platform to realize a server for measurement-device-independent quantum key distribution (MDI-QKD).

This effectively removed all possible detector side-channel attacks, which in turn 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.

A superconducting silicon chip is used as an untrusted relay server for secure quantum communication. By harnessing the unique low-dead-time feature of the waveguide integrated superconducting single-photon detectors (red wires with hairpin shape in the middle), optimal time-bin encoded Bell-state measurements (shown in blue and grey wave-like curves between four photons, indicated as red balls) are realized. These in turn enhance secure key rate of quantum communication. Courtesy of MaLab, Nanjing University

Researchers from two universities in China developed a quantum communications platform based on a silicon photonic chip with a superconducting nanowire single-photon detector (SNSPD). A superconducting silicon chip is used as an untrusted relay server for secure quantum communication. By harnessing the low-dead-time feature of the waveguide integrated superconducting single-photon detectors (red wires with hairpin shape in the middle), optimal time-bin encoded Bell-state measurements (in blue and gray wave-like curves between four photons, indicated as red balls) are realized. These in turn enhance secure key rate of quantum communication. Courtesy of MaLab, Nanjing University.

BAE Systems Sensor Solutions - Fairchild - FS Sensor Solutions 4/24 MR

In harnessing the advantages of this heterogeneously integrated system, the team obtained a high secure key rate with a 125-MHz clock rate.

“In contrast with GHz clock rate MDI-QKD experiments, our system does not require a complicated injection locking technique, which significantly reduces the complexity of the transmitter,” said Xiaodong Zheng, from the group of Xiao-Song Ma of Nanjing University and first author of the 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,” Ma said. “Combined with integrated QKD transmitters, a fully chip-based, scalable, and high-key-rate metropolitan quantum network should be realized in the near future.”

The research was published in Advanced Photonics (www.doi.org/10.1117/1.AP.3.5.055002).

Published: November 2021

Glossary

chip: 1. A localized fracture at the end of a cleaved optical fiber or on a glass surface. 2. An integrated circuit.
quantum: The term quantum refers to the fundamental unit or discrete amount of a physical quantity involved in interactions at the atomic and subatomic scales. It originates from quantum theory, a branch of physics that emerged in the early 20th century to explain phenomena observed on very small scales, where classical physics fails to provide accurate explanations. In the context of quantum theory, several key concepts are associated with the term quantum: Quantum mechanics: This is the branch of...
quantum key distribution: Quantum key distribution (QKD) is a method of secure communication that utilizes principles from quantum mechanics to establish a shared secret key between two parties, typically referred to as Alice and Bob, while detecting any potential eavesdropping attempts by a third party, commonly known as Eve. The fundamental principle behind QKD is the use of quantum properties, such as the superposition principle and the no-cloning theorem, to enable the distribution of cryptographic keys in a...
integrated photonics: Integrated photonics is a field of study and technology that involves the integration of optical components, such as lasers, modulators, detectors, and waveguides, on a single chip or substrate. The goal of integrated photonics is to miniaturize and consolidate optical elements in a manner similar to the integration of electronic components on a microchip in traditional integrated circuits. Key aspects of integrated photonics include: Miniaturization: Integrated photonics aims to reduce the...

Browse Cameras & Imaging, Lasers, Optical Components, Test & Measurement, and more.