The position of a device or agent is an important security credential in
today’s society, both online and in the real world. Unless in direct proximity,
however, the secure verification of a position is impossible without further
assumptions. This is true classically, but also in any future quantum-equipped
communications infrastructure. We show in this work that minimal quantum
resources, in the form of a single qubit, combined with classical communication
are sufficient to thwart quantum adversaries that pretend to be at a specific
position and have the ability to coordinate their action with entanglement.
More precisely, we show that the adversaries using an increasing amount of
entanglement can be combatted solely by increasing the number of classical bits
used in the protocol. The presented protocols are noise-robust and within reach
of current quantum technology.
