Possible realization of Josephson charge qubits in two coupled Bose-Einstein condensates

We demonstrate that two coupled Bose-Einstein condensates (BECs) at zero temperature can be used to realize a qubit which is the counterpart of Josephson charge qubits. The two BECs are weakly coupled and confined in an asymmetric double-well trap. When the "charging energy" of the system is much larger than the Josephson energy and the system is biased near a degeneracy point, the two BECs represent a qubit with two states differing only by one atom. The realization of the BEC qubits in realistic BEC experiments is briefly discussed.