Optical quantum fingerprinting

Fingerprinting is an information protocol for comparing messages when communication resources are limited: the fingerprint is shorter than the message, and a referee decides whether messages are equal by comparing received fingerprints. Fingerprinting has applications to protection of software. Quantum fingerprinting has been shown to be exponentially cheaper,in terms of communication resources, than classical fingerprinting with no shared resources between transmitters, and this exponential savings makes fingerprinting a particularly exciting quantum information protocol. We propose an experimental realization of one-qubit quantum fingerprinting,which is demonstrably superior to one-bit fingerprinting, and is feasible with existing technology.Whereas a quantum fingerprinting protocol employs a controlled-SWAP gate, the referee can succeed with a simple beam splitter to compare quantum fingerprints. Scaling to more qubits presents a challenge, which will be discussed.