Semi-device-independent framework based on natural physical assumptions

Understand

The semi-device-independent approach provides a framework for prepare-and-measure quantum protocols using devices whose behavior must not be characterized nor trusted, except for a single assumption on the dimension of the Hilbert space characterizing the quantum carriers.

• Here, we propose instead to constrain the quantum carriers through a bound on the mean value of a well-chosen observable.
• This modified assumption is physically better motivated than a dimension bound and closer to the description of actual experiments.
• In particular, we consider quantum optical schemes where the source emits quantum states described in an infinite-dimensional Fock space and model our assumption as an upper bound on the average photon number in the emitted states.