  An all-superconductor charge qubit enabling a radio-frequency readout of its
quantum state is described. The core element of the setup is a superconducting
loop which includes the single-Cooper-pair (Bloch) transistor. This circuit has
two functions: First, it operates as a charge qubit with magnetic control of
Josephson coupling and electrostatic control of the charge on the transistor
island. Secondly, it acts as the transducer of the rf electrometer, which
probes the qubit state by measuring the Josephson inductance of the transistor.
The evaluation of the basic parameters of this device shows its superiority
over the rf-SET-based qubit setup.
