Boson Sampling Private-Key Quantum Cryptography

Submitted to *Physical Review Letters* , (2019)

We introduce a quantum private-key encryption protocol based on multi-photon interference in linear optics networks. The scheme builds upon Boson Sampling, and we show that it is hard to break, even for a quantum computer. We present an information-theoretic proof of the security of our protocol against an eavesdropper with unlimited (quantum) computational power but time-limited quantum storage. This protocol is shown to be optimal in the sense that it asymptotically encrypts all the information that passes through the interferometer using an exponentially smaller private key. This is the first practical application of Boson Sampling in quantum communication. Our scheme requires only moderate photon numbers and is experimentally feasible with current technology.