  In this article we describe the characteristics of a large integrated linear
optical device containing Mach-Zehnder interferometers and describe its
potential use as a physically unclonable function. We propose that any tunable
interferometric device of practical scale will be intrinsically unclonable and
will possess an inherent randomness that can be useful for many practical
applications. The device under test has the additional use-case as a
general-purpose photonic manipulation tool, with various applications based on
the experimental results of our prototype. Once our tunable interferometric
device is set to work as a physically unclonable function, we find that there
are approximately 6.85x10E35 challenge-response pairs, where each challenge can
be quickly reconfigured by tuning the interferometer array for subsequent
challenges.
