Reducing parasitic interactions in a qubit grid for surface code error correction

Patent metadata

Field	Value
Publication number	US-11562280-B2
Application number	US-201716636522-A
Country	US
Kind code	B2
Filing date	Aug 9, 2017
Priority date	Aug 9, 2017
Publication date	Jan 24, 2023
Grant date	Jan 24, 2023

Abstract

Methods and systems for performing a surface code error detection cycle. In one aspect, a method includes initializing and applying Hadamard gates to multiple measurement qubits; performing entangling operations on a first set of paired qubits, wherein each pair comprises a measurement qubit coupled to a neighboring data qubit in a first direction; performing entangling operations on a second set of paired qubits, wherein each pair comprises a measurement qubit coupled to a neighboring data qubit in a second or third direction, the second and third direction being perpendicular to the first direction, the second direction being opposite to the third direction; performing entangling operations on a third set of paired qubits, wherein each pair comprises a measurement qubit coupled to a neighboring data qubit in a fourth direction, the fourth direction being opposite to the first direction; applying Hadamard gates to the measurement qubits; and measuring the measurement qubits.

First claim

The invention claimed is:

1. A method for performing a surface code error detection cycle, the method comprising:
initializing multiple measurement qubits from a system comprising a plurality of data qubits and a plurality of measurement qubits arranged as a two-dimensional grid, wherein each data qubit of the plurality of data qubits within the grid is coupled to neighboring measurement qubits through respective qubit couplers;
applying Hadamard quantum logic gates to the initialized measurement qubits;
performing multiple entangling operations on a first set of paired measurement and data qubits, wherein each pair in the first set of paired measurement and data qubits comprises a measurement qubit coupled to a neighboring data qubit in a first direction and wherein performing multiple entangling operations on the first set of paired measurement and data qubits comprises separating the pairs into multiple subsets of paired qubits, the multiple subsets comprising non-overlapping and non-adjacent pairs;
performing multiple entangling operations to a second set of paired measurement and data qubits, wherein each pair in the second set of paired measurement and data qubits comprises a measurement qubit coupled to a neighboring data qubit in a second or third direction, the second and third direction being perpendicular to the first direction, the second direction being opposite to the third direction;
performing multiple entangling operations to a third set of paired measurement and data qubits, wherein each pair in the third set of paired measurement and data qubits comprises a measurement qubit coupled to a neighboring data qubit in a fourth direction, the fourth direction being opposite to the first direction;
applying Hadamard quantum logic gates to the multiple measurement qubits; and
measuring the multiple measurement qubits to detect errors.

2. The method of claim 1 , further comprising applying Hadamard quantum logic gates to data qubits in the second set of paired measurement and data qubits that are paired with measurement qubits in the second direction.

3. The method of claim 1 , further comprising:
applying Hadamard quantum logic gates to data qubits in the second set of paired measurement and data qubits that are paired with measurement qubits in the second direction; and
applying Hadamard quantum logic gates to data qubits in the second set of paired measurement and data qubits that are paired with measurement qubits in the third direction.

4. The method of claim 1 , further comprising:
applying Hadamard quantum logic gates to data qubits in the second set of paired measurement and data qubits that are paired with measurement qubits in the third direction.

5. The method of claim 1 , wherein the entangling operations comprise controlled-Z quantum logic gates.

6. The method of claim 1 , wherein the multiple subsets comprise three subsets.

7. The method of claim 1 , wherein performing multiple entangling operations to the first set of paired measurement and data qubits comprises performing entangling operations on pairs of qubits in each of the multiple subsets in parallel.

8. The method of claim 7 , wherein performing entangling operations on pairs of qubits in each of the multiple subsets in parallel comprises detuning each measurement qubit in each subset in parallel.

9. The method of claim 1 , further comprising performing a leakage removal process on the measurement and data qubits.

10. The method of claim 9 , wherein performing leakage removal comprises swapping measurement and data qubits.

11. The method of claim 10 , wherein swapping measurement and data qubits comprises applying a controlled-Z plus swap quantum gate.

12. The method of claim 1 , further comprising performing a subsequent surface code error detection cycle, comprising:
initializing the multiple measurement qubits;
applying Hadamard quantum logic gates to the initialized measurement qubits;
performing entangling operations on the third set of paired data and measurement qubits in parallel;
performing entangling operations on the second set of paired data and measurement qubits in parallel;
performing entangling operations on the first set of paired data and measurement qubits in parallel;
applying Hadamard quantum logic gates to the multiple measurement qubits; and
measuring the multiple measurement qubits to detect errors.

13. A method for performing a surface code error detection cycle, the method comprising:
initializing multiple measurement qubits from a system comprising a plurality of data qubits and a plurality of measurement qubits arranged as a two-dimensional grid, wherein each data qubit of the plurality of data qubits within the grid is coupled to neighboring measurement qubits through respective qubit couplers;
applying Hadamard quantum logic gates to the initialized measurement qubits;
performing multiple entangling operations on a first set of paired measurement and data qubits, wherein each pair in the first set of paired measurement and data qubits comprises a measurement qubit coupled to a neighboring data qubit in a first direction;
performing multiple entangling operations to a second set of paired measurement and data qubits, wherein each pair in the second set of paired measurement and data qubits comprises a measurement qubit coupled to a neighboring data qubit in a second or third direction, the second and third direction being perpendicular to the first direction, the second direction being opposite to the third direction and wherein performing multiple entangling operations on the second set of paired measurement and data qubits comprises=separating the pairs into multiple subsets of paired qubits, the multiple subsets comprising overlapping and diagonally adjacent pairs;
performing multiple entangling operations to a third set of paired measurement and data qubits, wherein each pair in the third set of paired measurement and data qubits comprises a measurement qubit coupled to a neighboring data qubit in a fourth direction, the fourth direction being opposite to the first direction;
applying Hadamard quantum logic gates to the multiple measurement qubits; and
measuring the multiple measurement qubits to detect errors.

14. The method of claim 13 , wherein the multiple subsets comprise four subsets.

15. The method of claim 14 , wherein performing multiple entangling operations on the second set of paired measurement and data qubits comprises performing entangling operations on pairs of qubits in each of the multiple subsets in parallel.

16. The method of claim 15 , wherein performing entangling operations on pairs of qubits in each of the multiple subsets in parallel comprises detuning each measurement qubit in each subset in parallel.

17. A method, for performing a surface code error detection cycle, the method comprising:
initializing multiple measurement qubits from a system comprising a plurality of data qubits and a plurality of measurement qubits arranged as a two-dimensional grid, wherein each data qubit of the plurality of data qubits within the grid is coupled to neighboring measurement qubits through respective qubit couplers;
applying Hadamard quantum logic gates to the initialized measurement qubits;
performing multiple entangling operations on a first set of paired measurement and data qubits, wherein each pair in the first set of paired measurement and data qubits comprises a measurement qubit coupled to a neighboring data qubit in a first direction;
performing multiple entangling operations to a second set of paired measurement

Assignees

• Google Llc

Inventors

• Martinis John
• Barends Rami
• Fowler Austin Greig

Classifications

• H03K19/177

  arranged in matrix form · CPC title

• G06N10/00 Primary

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

• G06N10/20

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

• G06N10/40

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

• G06N10/70 Primary

  Quantum error correction, detection or prevention, e.g. surface codes or magic state distillation · CPC title