Here we analyze the practical implications of using Bell states produced through optical down-conversion in a quantum-data-hiding protocol. We show that the uncertainty in the production of Bell states through spontaneous parametric down-conversion should be taken into account, because it will cause difficulties for the encoding procedure. A set of extended Bell states and a generalized Bell-state analyzer are proposed to describe and analyze the possible states of two photons distributed in two paths. Then we present a method to integrate the above uncertainty of Bell-state preparation into the data-hiding procedure, when we encode the secret with the set of extended Bell states. These modifications greatly simplify the hider’s encoding operations, and thus pave the way for the implementation of quantum data hiding with present-day quantum optics.

• Received 11 March 2003

DOI:https://doi.org/10.1103/PhysRevA.68.044303