Error mitigation techniques

Patent metadata

Field	Value
Publication number	US-12165012-B2
Application number	US-202117926147-A
Country	US
Kind code	B2
Filing date	Jul 1, 2021
Priority date	Jul 2, 2020
Publication date	Dec 10, 2024
Grant date	Dec 10, 2024

Abstract

A method of mitigating errors in quantum computing, wherein the method comprises: performing (S101) an operation on the state of a qubit in a group of qubits a plurality of times, wherein the operation has a first error rate, and wherein each performance of the operation comprises: performing a first operation comprising: a gate operation, a symmetry operation, and a first basis operation; or performing a second operation comprising: the gate operation, the symmetry operation, and a second basis operation; wherein the first and second basis operations are different basis operations selected from a set of basis operations; and measuring the state of the qubit; wherein the probability of performing the first operation is a first probability, and the probability of performing the second operation is a second probability; obtaining (S102) a symmetry measurement for the group of qubits after each performance of the operation using the symmetry operation, wherein the group of qubits comprises a plurality of qubits; wherein the symmetry measurement is a first symmetry outcome if the number of errors is even or a second symmetry outcome if the number of errors is odd; obtaining (S103) a first state measurement by determining the average state of the qubit for the first symmetry outcome; obtaining (S104) a second state measurement by determining the average state of the qubit for the second symmetry outcome; fitting (S105) the first state measurement to a first curve having the form (I); fitting the second state measurement to a second curve having the form (II); wherein n is an error rate and A and γ are fitting parameters; and extrapolating (S106) the average state of the qubit at a second error rate using the first and second fitted curves; wherein the second error rate is lower than the first error rate.A⁢cosh⁡((1-γ)⁢n)cosh⁡(n)(I)A⁢sinh⁡((1-γ)⁢n)sinh⁡(n)(II)

First claim

The invention claimed is:

1. A method of mitigating errors in quantum computing, wherein the method comprises:
performing an operation on the state of a qubit in a group of qubits a plurality of times, wherein the operation has a first error rate, and wherein each performance of the operation comprises:
performing a first operation comprising: a gate operation, a symmetry operation, and a first basis operation; or
performing a second operation comprising: the gate operation, the symmetry operation, and a second basis operation;
wherein the first and second basis operations are different basis operations selected from a set of basis operations; and

measuring the state of the qubit;
wherein the probability of performing the first operation is a first probability, and the probability of performing the second operation is a second probability;

obtaining a symmetry measurement for the group of qubits after each performance of the operation using the symmetry operation, wherein the group of qubits comprises a plurality of qubits;
wherein the symmetry measurement is a first symmetry outcome if the number of errors is even or a second symmetry outcome if the number of errors is odd;

obtaining a first state measurement by determining the average state of the qubit for the first symmetry outcome;
obtaining a second state measurement by determining the average state of the qubit for the second symmetry outcome;
fitting the first state measurement to a first curve having the form

A
⁢

cosh
⁡
(

(

1
-
γ

)

⁢
n

)

cosh
⁡
(
n
)

;

fitting the second state measurement to a second curve having the form

A
⁢

sinh
⁡
(

(

1
-
γ

)

⁢
n

)

sinh
⁡
(
n
)

;

wherein n is an error rate and A and γ are fitting parameters; and

extrapolating the average state of the qubit at a second error rate using the first and second fitted curves;
wherein the second error rate is lower than the first error rate.

2. The method of mitigating errors according to claim 1 , wherein the first and second basis operations are selected from a set of basis operations comprising Pauli basis operations.

3. The method of mitigating errors according to claim 1 , wherein the first symmetry outcome is a pass and wherein the second symmetry outcome is a fail.

4. The method of mitigating errors according to claim 1 , wherein the qubit is a first qubit and wherein the method further comprises: performing the operation on the state of a second qubit in the group of qubits a plurality of times;
obtaining a third state measurement by determining the average state of the second qubit for the first symmetry outcome;
obtaining a fourth state measurement by determining the average state of the second qubit for the second symmetry outcome;
fitting the third state measurement to a third curve and the fourth state measurement to a fourth curve; and
extrapolating the average state of the second qubit at the second error rate using the third and fourth fitted curves.

5. A device for performing quantum computing calculations, comprising:
a selection module implemented on a computer readable memory medium comprising instructions which when executed by a computer cause the computer to preform steps comprising:
selecting a first basis operation from a set of basis operations with a first probability; and
selecting a second basis operation from a set of basis operations with a second probability;
wherein the first and second basis operations are different;

a quantum processor configured to perform an operation on the state of a qubit in a group of qubits a plurality of times, wherein the operation has a first error rate, and wherein each performance of the operation comprises:
performing a gate operation, a symmetry operation, and the selected basis operation;

a quantum measurement device configured to measure the state of the qubit;
a symmetry measurement device configured to measure the symmetry of the group of qubits after each performance of the operation using the symmetry operation, wherein the group of qubits comprises a plurality of qubits;
wherein the symmetry measurement is a first symmetry outcome if the number of errors is even or a second symmetry outcome if the number of errors is odd; and

a classical processor configured to:
obtain a first state measurement by determining the average state of the qubit for the first symmetry outcome and to obtain a second state measurement by determining the average state of the qubit for the second symmetry outcome;
fit the first state measurement to a first curve having the form

A
⁢

cosh
⁡
(

(

1
-
γ

)

⁢
n

)

cosh
⁡
(
n
)

;

fit the second state measurement to a second curve having the form

A
⁢

sinh
⁡
(

(

1
-
γ

)

Assignees

• Univ Oxford Innovation Ltd

Inventors

• Cai Zhenyu
• Benjamin simon

Classifications

• G06F17/18

  for evaluating statistical data {, e.g. average values, frequency distributions, probability functions, regression analysis (forecasting specially adapted for a specific administrative, business or logistic context G06Q10/04)} · CPC title

• G06F11/079

  Root cause analysis, i.e. error or fault diagnosis (in a hardware test environment G06F11/22; in a software test environment G06F11/36) · CPC title

• G06F11/0721

  within a central processing unit [CPU] · CPC title

• B82Y10/00

  Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic · CPC title

• G06F17/17 Primary

  Function evaluation by approximation methods, e.g. inter- or extrapolation, smoothing, least mean square method ({G06F17/18 takes precedence } ; interpolation for numerical control G05B19/18) · CPC title