Cryogenic thermometer based on a two-level systems (TLS)

Patent metadata

Field	Value
Publication number	US-12123786-B2
Application number	US-202117476832-A
Country	US
Kind code	B2
Filing date	Sep 16, 2021
Priority date	Sep 16, 2020
Publication date	Oct 22, 2024
Grant date	Oct 22, 2024

Abstract

Technology is disclosed herein that the enhances the measurability of on-chip temperature in a cryogenic quantum computing environment. In an implementation, transceiver circuitry sends a probe signal through a target device. A lumped-element resonator device that is proximate to the surface of the target device interacts with the probe signal and modulates the probe signal. Processing circuitry reads the probe signal through the target device, and responsively measures the resonance frequency of the lumped-element resonator device. The processing circuitry correlates the measured resonance frequency with a temperature and responsively determines the temperature of the target device.

First claim

What is claimed is:

1. A method of measuring a temperature of a target device that resides in a cryogenic environment and that comprises resonators that indicate qubit states, the method comprising:
sending a probe signal through the target device and a lumped-element resonator device, wherein the lumped-element resonator device is proximate to a surface of the target device and the lumped-element resonator device is configured to interact with the probe signal;
reading the probe signal transmitted through the target device and the lumped-element resonator device and responsively measuring a resonance frequency of the lumped-element resonator device; and
determining the temperature of the target device by correlating the resonance frequency of the lumped-element resonator device with the temperature of the target device.

2. The method of claim 1 , wherein the lumped-element resonator device is physically coupled to the surface of the target device.

3. The method of claim 1 , wherein the lumped-element resonator device is proximate to the target device without physically contacting the target device.

4. The method of claim 1 , wherein determining the temperature of the target device by correlating the resonance frequency of the lumped-element resonator device with the temperature of the target device comprises applying a calibration curve to the resonance frequency of the lumped-element resonator device and responsively determining the temperature of the target device based on the calibration curve.

5. The method of claim 1 , wherein reading the probe signal transmitted through the target device and the lumped-element resonator device and responsively measuring the resonance frequency of the lumped-element resonator device comprises sweeping the probe signal in a frequency band, measuring the probe signal transmitted through the target device and the lumped-element resonator device, calculating a transmission coefficient for the measured probe signal, and fitting the transmission coefficient to a resonator circuit model to determine the resonance frequency of the lumped-element resonator device.

6. The method of claim 1 , wherein the lumped-element resonator device comprises a meandering inductor, a coupling capacitor, and an interdigitated capacitor; and the meandering inductor, the coupling capacitor, and the interdigitated capacitor are configured to interact with the probe signal.

7. The method of claim 6 , wherein the meandering inductor, the coupling capacitor, and the interdigitated capacitor comprise:
a Silicon substrate, a superconducting Niobium film that is deposited on the Silicon substrate, and an amorphous dielectric that is attached to the Silicon substrate and the superconducting Niobium film; and wherein:
the amorphous dielectric comprises at least one of:
a naturally formed oxide layer on the Silicon substrate and the superconducting Niobium film; or
a deposited silicon oxide and/or silicon nitride layer on the Silicon substrate and the superconducting Niobium film.

8. The method of claim 6 , further comprising:
interacting with the probe signal; and
responsively modulating a phase and an amplitude of the probe signal to carry information that indicates the resonance frequency of the lumped-element resonator device.

9. An apparatus configured to measure a temperature of a target device that resides in a cryogenic environment and that comprises resonators that indicate qubit states, the apparatus comprising:
transceiver circuitry configured to
send a probe signal through the target device;

a lumped-element resonator device configured to:
interact with the probe signal; and
modulate a phase and an amplitude of the probe signal, wherein the lumped-element resonator device is proximate to a surface of the target device; and

processing circuitry configured to:
read the probe signal transmitted through the target device;
responsively measure a resonance frequency of the lumped-element resonator device; and
determine the temperature of the target device by correlating the resonance frequency of the lumped-element resonator device with the temperature of the target device.

10. The apparatus of claim 9 , wherein the lumped-element resonator device is physically coupled to the surface of the target device.

11. The apparatus of claim 9 , wherein the lumped-element resonator device is proximate to the target device without physically contacting the target device.

12. The apparatus of claim 9 , wherein the processing circuitry is configured to:
apply a calibration curve to the resonance frequency of the lumped-element resonator device; and
responsively determine the temperature of the target device based on the calibration curve.

13. The apparatus of claim 9 , wherein the processing circuitry is configured to:
sweep the probe signal in a frequency band;
measure the probe signal transmitted through the target device and the lumped-element resonator device;
calculate a transmission coefficient for the measured probe signal; and
fit the transmission coefficient to a resonator circuit model to determine the resonance frequency of the lumped-element resonator device.

14. The apparatus of claim 9 , wherein the lumped-element resonator device comprises a meandering inductor, a coupling capacitor, and an interdigitated capacitor.

15. The apparatus of claim 14 , wherein the meandering inductor, the coupling capacitor, and the interdigitated capacitor comprise:
a Silicon substrate, a superconducting Niobium film that is deposited on the Silicon substrate, and an amorphous dielectric that is attached to the Silicon substrate and the superconducting Niobium film; and wherein:
the amorphous dielectric comprises at least one of:
a naturally formed oxide layer on the Silicon substrate and the superconducting Niobium film; or
a deposited silicon oxide and/or silicon nitride layer on the Silicon substrate and the superconducting Niobium film.

16. The apparatus of claim 14 , wherein the meandering inductor, the coupling capacitor, and the interdigitated capacitor are configured to:
interact with the probe signal; and
responsively modulate the phase and the amplitude of the probe signal to carry information that indicates the resonance frequency of the lumped-element resonator device.

17. An apparatus configured to measure a temperature of a qubit resonator device that resides in a cryogenic environment, the apparatus comprising:
transceiver circuitry configured to
send a probe signal through the qubit resonator device;

the qubit resonator device being configured to:
interact with the probe signal; and
modulate a phase and an amplitude of the transmitted probe signal,

wherein the qubit resonator device comprises one or more qubit resonators and a temperature resonator that resonates at a different frequency than the one or more qubit resonators; and
processing circuitry configured to:
read the probe signal through the qubit resonator device;
measure a resonance frequency of the temperature resonator; and
responsively determine the temperature of the qubit resonator device by correlating the resonance frequency of the temperature resonator with the temperature of the qubit resonator device.

18. The apparatus of claim 17 , wherein the temperature resonator comprises a lumped-element resonator configured to modulate the phase and amplitude of the probe signal to carry information that indicates the resonance frequency of the temperature resonator.

19. The apparatus of claim 17 , wherein t

Assignees

• Univ Colorado Regents
• Univ Colorado Regents
• National Institute Of Standards And Tech

Inventors

• Gao Jiansong
• Malnou Maxime Bernard Jacques
• Vissers Michael Robert
• Wheeler Jordan

Classifications

• G01K1/14

  Supports; Fastening devices; Arrangements for mounting thermometers in particular locations · CPC title

• G01K13/008

  using microstructures, e.g. made of silicon · CPC title

• G01K7/32

  using change of resonant frequency of a crystal · CPC title

• G01K7/006 Primary

  using superconductive elements · CPC title