Patent ID: 7268576

Claim:
A method of reading out a quantum state of a qubit in a device, wherein said device comprises: the qubit, wherein the qubit comprises: a superconducting loop; a plurality of Josephson junctions, wherein each Josephson junction in said plurality of Josephson junctions interrupts a different portion of said superconducting loop; and a plurality of islands, said plurality of islands comprising a first island and a second island, wherein each island in the plurality of islands is defined by a different portion of the superconducting loop and wherein each island in the plurality of islands is bound by a different adjacent pair of Josephson junctions in said plurality of Josephson junctions; a first mechanism configured to tune a first gate charge of said first island; and a second mechanism configured to tune a second gate charge of said second island; the method comprising: (A) tuning said first gate charge of said first island with said first mechanism and said second gate charge of said second island with said second mechanism so that the first gate charge and the second gate charge are exactly or substantially equal; and (B) reading out the quantum state of said qubit using a readout mechanism capacitively coupled to said first island and said second island.