  A current-biased low-temperature superconducting Josephson junction (JJ) is
dynamically describable by the quantized motion of a fictitious particle in a
"washboard" potential. The long coherence time of tightly-bound states in the
washboard potential of a JJ has prompted the effort to couple JJs and operate
them as entangled qubits, capable of forming building blocks of a scalable
quantum computer. Here we consider a hitherto unexplored quantum aspect of
coupled JJs: the ability to produce Einstein-Podolsky-Rosen (EPR) entanglement
of their continuous variables, namely, their magnetic fluxes and induced
charges. Such entanglement, apart from its conceptual novelty, is the
prerequisite for a far-reaching goal: teleportation of the flux and charge
variables between JJs, implementing the transfer of an unknown quantum state
along a network of such devices.
