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US 7,443,720 B2Granted
Method and circuit for reading quantum state
AssigneesRiken, NEC Corporation
InventorsOleg Astafiev, Yuri Pashkin, Jaw-Shen Tsai
Life of this patent
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Abstract
A single electron-transistor is used to read out charge states of two coupled qubits formed by two Cooper pair boxes. Detection is made about a gate voltage shift of the peak of the current that flows in the single electron transistor in accordance with the charge states. Since the current peak position varies depending on the particular charge state, all four charge states can be independently measured, or read out.
Claims7
A quantum-state readout circuit comprising:
- two Cooper pair boxes;
- two capacitors that are coupled to the two Cooper pair boxes, respectively;
- and
- reading means that is coupled to the capacitors and that comprises a single-electron transistor,
- wherein the two capacitors coupled to the two Cooper pair boxes have capacitances that are different from each other.
2 more elements
A quantum-state readout method comprising:
- preparing two Cooper-pair boxes coupled to each other through a capacitor or an inductor, two capacitors that have different capacitances, and a single-electron transistor that is coupled to the two Cooper-pair boxes through the respective capacitors and that has an island electrode and a gate electrode adjacent to the island electrode, each of the two Cooper-pair boxes involving two charge states;
- detecting a peak of an electrical current flowing from each of the Cooper-pair boxes to the island electrode of the single electron transistor through each of the two capacitors;
- and
- converting the peak of the electrical current into a shift in a gate voltage at the gate electrode of the single electron transistor to read out the charge states of the two Cooper-pair boxes.
1 more element
Dependencies are inferred from the claim text.