Certifying the building blocks of quantum computers from Bell's theorem. (arXiv:1802.02170v1 [quant-ph])

The power of quantum computers relies on the capability of their components
to maintain faithfully and process accurately quantum information. Since this
property eludes classical certification methods, fundamentally new protocols
are required to guarantee that elementary components are suitable for quantum
computation. These protocols must be device-independent, that is, they cannot
rely on a particular physical description of the actual implementation if one
is to qualify a block for all possible usages. Bell's theorem has been proposed
to certify, in a device-independent way, blocks either producing or measuring
quantum states. In this manuscript, we provide the missing piece: a method
based on Bell's theorem to certify coherent operations such as storage,
processing and transfer of quantum information. This completes the set of tools
needed to certify all building blocks of a quantum computer. Our method is
robust to experimental imperfections, and so can be readily used to certify
that today's quantum devices are qualified for usage in future quantum
computers.

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