Characterization and measurement of superconducting structures

• US 7,002,174 B2
• Filed: 12/16/2002
• Issued: 02/21/2006
• Est. Priority Date: 12/18/2001
• Status: Active Grant

• Current Assignee: D-Wave Systems Inc. (D-Wave Quantum, Inc.)
• Original Assignee: D-Wave Systems Inc. (D-Wave Quantum, Inc.)
• Inventors: Steininger, Miles F. H., Grajcar, Miroslav, Il'ichev, Evgeni, Zagoskin, Alexandre M.
• Primary Examiner(s): Flynn, Nathan J.
• Assistant Examiner(s): Wilson, Scott R.
• Application Number:
  US10/321,065
• Publication Number:
  US 20030224944A1
• Time in Patent Office: 1,163 Days
• Field of Search: 257/14, 257/9, 257 31- 36
• US Class Current: 257/14
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G01R 33/0358 coupling the flux to the SQUID gradiometer coils G01R33/022; coils with superconductive winding H01F6/06
• CPC Class Codes: G06N 10/00 Quantum computing, i.e. information processing based on quantum-mechanical phenomena
• CPC Class Codes: H10N 69/00 Integrated devices, or assemblies of multiple devices, comprising at least one superconducting element covered by group H10N60/00
• CPC Class Codes: Y10S 977/933 Spintronics or quantum computing

Abstract

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.

Claims

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.