Quantum coin flipping which cannot be biased by dishonest parties exploiting information loss is reported in Nature Communications this week. This could lead to its use in quantum cryptography, for procedures such as mail certification and remote contract signing where communicating parties do not trust each other. Quantum cryptography — which uses the quantum states of light particles called photons to encode information for transmission — exploits the fact that measurements cannot be made of a quantum system without disturbing it. However, practical systems are subject to loss of quantum data, and this means that a dishonest party can completely bias the outcome of a quantum coin flip. Felix Bussieres and colleagues show a way to overcome this problem, so that the information loss cannot be used to cheat more effectively.
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