High-Rate and Computationally-Efficient Seedless Extractors

Title: High-Rate and Computationally-Efficient Seedless Extractors for Device-Independent Quantum Cryptography

Date: Oct 12 2026 Monday (US holiday) 10:00 am - Noon EDT

Summary: Device-independent (DI) quantum cryptography provides secure cryptography with minimal trust in, or characterisation of, the used quantum devices. An essential component of DI protocols is the use of randomness extractors for privacy amplification, but these typically require an initial seed of randomness that introduces a potential vulnerability. To solve this problem, the security of seedless extractors was proven in Quantum 9, 1654 (2025). The core idea was to use the Bell violation of the raw data, rather than its min-entropy, as the extractor promise. However, the large fluctuations in the Bell inequality used required many rounds to precisely estimate the Bell violation, consuming substantial randomness and making the protocol very inefficient. In this work, we present a new proof technique based on a truncation method that allows the user to estimate the protocol parameters with an asymptotically vanishing fraction of rounds and, as a consequence, achieves the optimal rate of one key bit per singlet. Notably, we prove this result using seedless extractors that can be implemented efficiently.

Speaker:

Simone Lin is a PhD student at University College London, supervised by Professor Lluís Masanes. She became interested in quantum information during her master’s degree at the University of Bristol, where she studied tripartite nonlocality. Her research interests span several areas of quantum information theory and cryptography, including the classical simulation of quantum correlations. She is currently developing non-modular security proofs for device-independent quantum cryptographic protocols.