Characterization and measurement of superconducting structures
View Patent ↗A structure comprising a tank circuit inductively coupled to a flux qubit or a phase qubit. In some embodiments, a low temperature preamplifier is in electrical communication with the tank circuit. The tank circuit comprises an effective capacitance and an effective inductance that are in parallel or in series. In some embodiments, the effective inductance comprises a multiple winding coil of wire. A method that includes the steps of (i) providing a tank circuit and a phase qubit that are inductively coupled, (ii) reading out a state of the phase qubit, (iii) applying a flux to the phase qubit that approaches a net zero flux, (iv) increasing a level of flux applied to the phase qubit, and (v) observing a response of the tank circuit in a readout device.
1. A method comprising:
reading out a state of a phase qubit that is inductively coupled to a tank circuit;
applying a first flux to said phase qubit, wherein said first flux approaches a net zero flux;
applying a second flux to said phase qubit, wherein said second flux has an increased level of flux relative to said first flux; and
observing a response of said tank circuit in a readout device to said second flux, wherein said observing comprises monitoring an existence of a metastable state of said phase qubit or a disappearance of a metastable state of said phase qubit.
2. A method comprising:
reading out a state of a phase qubit that is inductively coupled to a tank circuit;
applying a first flux to said phase qubit, wherein said first flux approaches a net zero flux;
applying a second flux to said phase qubit, wherein said second flux has an increased level of flux relative to said first flux; and
observing a response of said tank circuit in a readout device to said second flux, wherein said observing comprises monitoring a hysteretic behavior of the tank circuit.
3. A method comprising:
reading out a state of a phase qubit that is inductively coupled to a tank circuit;
applying a first flux to said phase qubit, wherein said first flux approaches a net zero flux;
applying a second flux to said phase qubit, wherein said second flux has an increased level of flux relative to said first flux; and
observing a response of said tank circuit in a readout device to said second flux, wherein said observing comprises determining a magnitude of a tunneling rate of the phase qubit.