Balthazar Bauer

We present complementary theoretical and experimental contributions bridging quantum cryptography and communication complexity. In our theory paper, we introduce a hybrid key distribution protocol achieving everlasting security while transmitting multiple photons per channel use, potentially surpassing fundamental QKD rate limits. The security proof for this protocol is based on a reduction that leverages the quantum advantage in communication cost between classical and quantum one-way communication complexity problems. Building on this theoretical foundation, our experimental work investigates the feasibility of demonstrating such quantum advantages in communication complexity using a reconfigurable and scalable optical platform based on wavefront shaping techniques.

We introduce an explicit construction for a key distribution protocol in the Quantum Computational Timelock (QCT) security model, where one assumes that computationally secure encryption may only be broken after a time much longer than the coherence time of available quantum memories. Taking advantage of the QCT assumptions, we build a key distribution protocol called HM-QCT from the Hidden Matching problem for which there exists an exponential gap in one-way communication complexity between classical and quantum strategies.