  Concurrent remote entanglement of distant, non-interacting quantum entities
is a crucial function for quantum information processing. In contrast with the
existing protocols which employ addition of signals to generate entanglement
between two remote qubits, the protocol we present is based on multiplication
of signals. This protocol can be straightforwardly implemented by a novel
Josephson junction mixing circuit. Our scheme would be able to generate
provable entanglement even in presence of practical imperfections: finite
quantum efficiency of detectors and undesired photon loss in current
state-of-the-art devices.
