Quantum Repeaters and Quantum Networks

Quantum networks open up functions far beyond those of the classical internet, but transmitting quantum information over long distances is notably more complex. While classical networks rely on fiber optics, the no-cloning theorem prevents direct signal amplification in quantum communication, complicating data relay. To overcome these issues, our group explores various types of quantum repeaters designed to enhance signal strength without violating quantum principles.

Quantum Repeaters Using Bosonic Error Correcting Codes

One promising approach leverages quantum error correction codes specifically tailored for optical channels. Bosonic codes, like the Gottesman-Kitaev-Preskill (GKP) code, encode information in the quadratures of the light field. The GKP code is especially effective at mitigating losses by structuring information in the optical phase space. Our research aims to integrate this with discrete variable codes for robust, multi-level encoding that improves communication fidelity.

Entanglement Distillation

Efficient entanglement distribution is crucial for quantum networking, and our group focuses on optimizing this through entanglement distillation. Distillation involves refining high-quality entanglement from a noisier source by using local operations and classical communication to isolate the best entangled states. By developing and testing new distillation schemes, we work to push the limits of practical entanglement, enhancing the reliability of quantum communication networks.

Quantum Key Distribution (QKD)

QKD is one of the most mature applications of quantum networks, enabling the secure distribution of cryptographic keys. This security is grounded in quantum mechanics through the uncertainty principle and the monogamy of entanglement. In our lab, we focus on creating practical QKD protocols and refining post-processing techniques to ensure robust, secure communication—even with realistic noise factors in experimental settings.