Flux-tunable qubit device with multiple Josephson junctions

Patent metadata

Field	Value
Publication number	US-10050630-B2
Application number	US-201615241783-A
Country	US
Kind code	B2
Filing date	Aug 19, 2016
Priority date	Aug 19, 2016
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

In a general aspect, a qubit device includes two circuit loops. In some aspects, a first circuit loop includes a first Josephson junction, a second circuit loop includes a second Josephson junction, and the first and second loops are configured to receive a magnetic flux that defines a transition frequency of a qubit device. In some aspects, a quantum integrated circuit includes an inductor connected between a first circuit node and a second circuit node; the first Josephson junction connected in parallel with the inductor between the first circuit node and the second circuit node; and the second Josephson junction connected in parallel with the inductor between the first circuit node and the second circuit node.

First claim

What is claimed is:

1. A qubit device comprising:
an inductor connected between a first circuit node and a second circuit node;
a first Josephson junction connected in parallel with the inductor between the first circuit node and the second circuit node, wherein the first Josephson junction has a first Josephson energy;
a second Josephson junction connected in parallel with the inductor between the first circuit node and the second circuit node, wherein the second Josephson junction has a second Josephson energy;
a first circuit loop that includes the first Josephson junction; and
a second circuit loop that includes the second Josephson junction, wherein the first and second circuit loops are configured to receive, during operation of the qubit device, a magnetic flux that controls a qubit frequency of the qubit device, wherein:
the first circuit loop defines a first magnetic flux area to receive a first portion of the magnetic flux;
the second circuit loop defines a second magnetic flux area to receive a second portion of the magnetic flux; and
the qubit device is configured such that a Josephson energy ratio of the qubit device substantially equals a magnetic flux ratio of the qubit device minus one, the magnetic flux ratio being the ratio of the first portion of the magnetic flux to the second portion of the magnetic flux, the Josephson energy ratio being the ratio of the first Josephson energy to the second Josephson energy.

2. The qubit device of claim 1 , wherein:
the first circuit loop includes the first Josephson junction and the second Josephson junction; and
the second circuit loop includes the inductor and the second Josephson junction.

3. The qubit device of claim 1 , wherein:
the first circuit loop includes the first Josephson junction and the inductor; and
the second circuit loop includes the second Josephson junction and the inductor.

4. The qubit device of claim 1 ,
wherein the Josephson energy ratio is substantially an integer value.

5. The qubit device of claim 1 ,
wherein the first and second Josephson energies are unequal.

6. The qubit device of claim 1 ,
wherein the magnetic flux ratio is substantially an integer value.

7. The qubit device of claim 1 , wherein the qubit frequency as a function of the magnetic flux comprises a minimum, a maximum, and a flux sweet spot between the minimum and maximum.

8. The qubit device of claim 1 , wherein the first Josephson junction and the second Josephson junction each comprise a respective parasitic capacitance in parallel with the inductor.

9. The qubit device of claim 1 , wherein the inductor comprises a superinductor that includes a serial array of Josephson junctions.

10. The qubit device of claim 1 , wherein the inductor comprises a superinductor that includes a superconducting wire.

11. A qubit device comprising:
an inductor connected between a first circuit node and a second circuit node;
a first Josephson junction connected in parallel with the inductor between the first circuit node and the second circuit node, wherein the first Josephson junction has a first Josephson energy;
a second Josephson junction connected in parallel with the inductor between the first circuit node and the second circuit node, wherein the second Josephson junction has a second Josephson energy;
a first circuit loop that includes the first Josephson junction; and
a second circuit loop that includes the second Josephson junction, wherein the first and second circuit loops are configured to receive, during operation of the qubit device, a magnetic flux that controls a qubit frequency of the qubit device, wherein:
the first circuit loop defines a first magnetic flux area to receive a first portion of the magnetic flux;
the second circuit loop defines a second magnetic flux area to receive a second portion of the magnetic flux; and
the qubit device is configured such that a Josephson energy ratio of the qubit device substantially equals a magnetic flux ratio of the qubit device minus one, the magnetic flux ratio being the ratio of the second portion of the magnetic flux to the first portion of the magnetic flux, the Josephson energy ratio being the ratio of the first Josephson energy to the second Josephson energy.

12. The qubit device of claim 11 , wherein:
the first circuit loop includes the first Josephson junction and the second Josephson junction; and
the second circuit loop includes the inductor and the second Josephson junction.

13. The qubit device of claim 11 , wherein:
the first circuit loop includes the first Josephson junction and the inductor; and
the second circuit loop includes the second Josephson junction and the inductor.

14. The qubit device of claim 11 , wherein the Josephson energy ratio is substantially an integer value.

15. The qubit device of claim 11 , wherein the first and second Josephson energies are unequal.

16. The qubit device of claim 11 , wherein the magnetic flux ratio is substantially an integer value.

17. The qubit device of claim 11 , wherein the qubit frequency as a function of the magnetic flux comprises a minimum, a maximum, and a flux sweet spot between the minimum and maximum.

18. The qubit device of claim 11 , wherein the first Josephson junction and the second Josephson junction each comprise a respective parasitic capacitance in parallel with the inductor.

19. The qubit device of claim 11 , wherein the inductor comprises a superinductor that includes a serial array of Josephson junctions.

20. The qubit device of claim 11 , wherein the inductor comprises a superinductor that includes a superconducting wire.

21. A quantum integrated circuit comprising:
a first circuit loop defining a first magnetic flux area configured to receive a first magnetic flux during operation of the quantum integrated circuit, the first circuit loop comprising a first Josephson junction having a first Josephson energy; and
a second circuit loop defining a second magnetic flux area configured to receive a second magnetic flux during operation of the quantum integrated circuit, the second circuit loop comprising a second Josephson junction having a second Josephson energy, the second Josephson junction being connected in parallel with the first Josephson junction;
wherein at least one of the first circuit loop or the second circuit loop comprises an additional circuit element connected in parallel with the first Josephson junction and the second Josephson junction;
wherein a Josephson energy ratio of the first and second circuit loops substantially equals a magnetic flux ratio of the first and second circuit loops minus one, the Josephson energy ratio being the ratio of the first Josephson energy to the second Josephson energy, the magnetic flux ratio being either the ratio of the first magnetic flux to the second magnetic flux or the ratio of the second magnetic flux to the first magnetic flux.

22. The quantum integrated circuit of claim 21 , wherein the first and second magnetic fluxes control a transition frequency between quantum energy states in the quantum integrated circuit.

23. The quantum integrated circuit of claim 21 , wherein:
the first circuit loop includes the first Josephson junction and the second Josephson junction; and
the second circuit loop includes the additional circuit element and the second Josephson junction.

24. The quantum integrated circuit of claim 21 , wherein:
the first circuit loop includes the firs

Assignees

• Rigetti & Co Inc
• Rigetti & Co Inc

Inventors

• Reagor Matthew J
• Sete Eyob A
• Rigetti Chad T

Classifications

• H03K19/195 Primary

  using superconductive devices · CPC title

• G06N99/002

  Physics · mapped topic

• G06N10/40

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

• G06N10/20

  Models of quantum computing, e.g. quantum circuits or universal quantum computers · CPC title