Current device readout system

Patent metadata

Field	Value
Publication number	US-10884033-B2
Application number	US-201916277560-A
Country	US
Kind code	B2
Filing date	Feb 15, 2019
Priority date	Feb 15, 2019
Publication date	Jan 5, 2021
Grant date	Jan 5, 2021

Abstract

One example includes a current device readout system. The system includes a tunable resonator having a resonant frequency that is associated with a current state of a current device. The tunable resonator can be configured to receive a tone signal having a predetermined frequency from a feedline to determine the current state of the current device. The system also includes an isolation device inductively interconnecting the tunable resonator and the current device. The isolation device can be tunable to isolate the current device in a first state and to facilitate the determination of the current state of the current device in a second state.

First claim

What is claimed is:

1. A current device readout system comprising:
a tunable resonator having a resonant frequency that is associated with a current state of a current device, the tunable resonator being configured to receive a tone signal having a predetermined frequency from a feedline to determine the current state of the current device; and
an isolation device configured as a quantum flux parametron (QFP) inductively interconnecting the tunable resonator and the current device, the QFP being tunable based on a static flux to set a threshold to facilitate amplification of the current state of the current device, wherein the QFP is configured to isolate the current device in a first state and the tunable resonator and is configured to provide an amplified current state of the current device in a second state to the tunable resonator to facilitate the determination of the current state of the current device in the second state.

2. The system of claim 1 , wherein the current device is configured as a flux qubit, such that the first current state corresponds to a first flux state that is based on a first current direction of a current loop associated with the flux qubit, and such that the second current state corresponds to a second flux state that is based on a second current direction of the current loop associated with the flux qubit.

3. The system of claim 1 , wherein the QFP is configured as a tunable coupler with respect to the current device and with respect to the tunable resonator.

4. The system of claim 3 , wherein the QFP is inductively coupled to the tunable resonator and to the current device, wherein the QFP is tunable to provide flux-isolation in a first QFP state and to amplify the current state of the current device in a second QFP state to store the current state in the QFP in the second QFP state, the amplified current state of the current device in the second state being inductively provided to the tunable resonator via the QFP to facilitate the determination of the current state of the current device in response to the tone signal.

5. The system of claim 4 , wherein the QFP is inductively tuned to provide a mutual inductance between the tunable resonator and the current device to zero in the first QFP state.

6. The system of claim 5 , wherein the QFP is inductively tuned to a flux of Φ 0 /2 to provide the mutual inductance between the tunable resonator and the current device to zero in the QFP first state.

7. The system of claim 4 , wherein the QFP is adiabatically inductively tuned to a flux of Φ 0 to amplify the current state of the current device in the second QFP state to store the current state in the QFP in the second QFP state.

8. The system of claim 3 , wherein the QFP comprises a compound Josephson junction (CJJ) that is configured to be inductively tuned between the first QFP state and the second QFP state.

9. The system of claim 8 , wherein the QFP further comprises an inductor that is tuned by the static flux to set the threshold to facilitate amplifying the current state of the current device as one of the first current state and the second current state in the second state of the QFP, wherein the first current state sets the resonant frequency of the tunable resonator to a first resonant frequency and the second current state sets the resonant frequency of the tunable resonator to a second resonant frequency.

10. The system of claim 1 , wherein the static flux is a first static flux, the tunable resonator being tuned via a second static flux to set the resonant frequency of the tunable resonator to a first predetermined frequency corresponding to an on-resonant frequency associated with the first current state of the current device.

11. The system of claim 1 , wherein the QFP is a first QFP of a plurality of QFPs, each of the plurality of QFPs being arranged in a sequential inductive arrangement between the tunable resonator and the current device.

12. The system of claim 1 , wherein the QFP is a first QFP of a plurality of QFPs, wherein the first QFP is inductively coupled to a first current device of a plurality of current devices, wherein each of the plurality of QFPs inductively interconnects a respective one of the plurality of current devices.

13. A method for reading a current state of a current device, the method comprising:
providing a first flux bias to a quantum flux parametron (QFP) that inductively interconnects a tunable resonator and the current device to set the QFP to a first QFP state to inductively isolate the tunable resonator and the current device, the QFP being tunable based on a static flux to set a threshold to facilitate amplification of the current state of the current device, wherein the current state of the current device corresponds to one of a first current state and a second current state;
providing a second bias flux to the QFP to set the QFP to a second QFP state to set a resonant frequency of the tunable resonator associated with the current state of the current device, the QFP being configured to provide an amplified current state of the current device in the second current state to the tunable resonator based on the second bias flux;
providing to the tunable resonator a tone signal having a predetermined frequency from a feedline; and
monitoring the feedline in response to providing the tone signal to determine the current state of the current device.

14. The method of claim 13 , wherein the current device is configured as a flux qubit, such that the first current state corresponds to a first flux state that is based on a first current direction of a current loop associated with the flux qubit, and such that the second current state corresponds to a second flux state that is based on a second current direction of the current loop associated with the flux qubit.

15. The method of claim 13 , wherein providing the first bias flux comprises providing the first bias flux to the QFP to inductively tune the QFP to a flux of approximately Φ 0 /2 to provide a mutual inductance between the tunable resonator and the current device to approximately zero in the first QFP state, and wherein providing the second bias flux comprises adiabatically increasing from the first bias flux to the second bias flux to adiabatically increase a flux of the QFP to approximately Φ 0 to amplify the current state of the current device in the second QFP state to store the current state in the QFP in the second QFP state.

16. The method of claim 13 , wherein providing the first bias flux and second bias flux to the QFP comprises providing the first bias flux and the second bias flux to a compound Josephson junction (CJJ) that is configured to be inductively tuned between the first QFP state and the second QFP state.

17. A current device readout system comprising:
a tunable resonator having a resonant frequency that is associated with a current state of a flux qubit, the tunable resonator being configured to receive a tone signal having a predetermined frequency from a feedline to determine the current state of the flux qubit; and
a quantum flux parametron (QFP) inductively interconnecting the tunable resonator and the flux qubit, the QFP being tunable to inductively isolate the flux qubit and the tunable resonator in a first QFP state and to amplify the current state of the current device to facilitate the determination of the current state of the current device in a second QFP state, wherein the QFP comprises an inductor that is tuned by a static flux to set a threshold to facilitate amplifying the current state of the current device as one a first cu

Assignees

• Przybysz Anthony Joseph
• Ferguson David George
• Khalil Moe S
• Northrop Grumman Systems Corp

Inventors

• Przybysz Anthony Joseph
• Ferguson David George
• Khalil Moe S

Classifications

• G06N10/40 Primary

  Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control · CPC title

• G01R19/0092 Primary

  Measuring current only · CPC title

• G01R33/035

  using superconductive devices · CPC title

• G11C11/44

  using super-conductive elements, e.g. cryotron · CPC title

• G06N10/00

  Quantum computing, i.e. information processing based on quantum-mechanical phenomena · CPC title