  We experimentally demonstrate, using qubits encoded in photon polarization,
that if two parties share a single reference direction and use locally
orthogonal measurements they will always violate a Bell inequality, up to
experimental deficiencies. This contrasts with the standard view of Bell
inequalities in which the parties need to share a complete reference frame for
their measurements. Furthermore, we experimentally demonstrate that as the
reference direction degrades the probability of violating a Bell inequality
decreases smoothly to (39.7 +/- 0.1) % in the limiting case that the observers
do not share a reference direction. This result promises simplified
distribution of entanglement between separated parties, with applications in
fundamental investigations of quantum physics and tasks such as quantum
communication.
