Methods and devices for decoding quantum states

Patent metadata

Field	Value
Publication number	US-11263076-B2
Application number	US-201916728952-A
Country	US
Kind code	B2
Filing date	Dec 27, 2019
Priority date	Jun 30, 2017
Publication date	Mar 1, 2022
Grant date	Mar 1, 2022

Abstract

A method and a device for correcting quantum state information are disclosed. A decoder receives information identifying syndrome values for a plurality of entangled qubit states represented by a graph state with a respective edge of the graph state corresponding to a respective qubit state of the plurality of entangled qubit states. The decoder repeats identifying one or more clusters of qubit states and/or syndrome states in the graph state until all of the one or more identified clusters are determined to be valid while increasing a size of a respective cluster each time the identifying operation is performed. The decoder reconstructs one or more qubit states and/or syndrome states for respective clusters; and stores information identifying the one or more reconstructed qubit states and/or syndrome states.

First claim

What is claimed is:

1. A method, comprising:
at a decoder of a quantum computing system:
receiving information identifying syndrome values for a plurality of entangled qubit states represented by a graph state with a respective edge of the graph state corresponding to a respective qubit state of the plurality of entangled qubit states, the graph state having at least one boundary with open edges;
identifying one or more clusters of at least one of: qubit states and syndrome states in the graph state;
repeating the identifying operation until all of the one or more identified clusters are determined to be valid, at least one cluster of the one or more clusters identified at n+1 generation including a corresponding cluster of the one or more clusters identified at n generation and at least a portion of qubit states or syndrome states adjacent, in the graph state, to the corresponding cluster of the one or more clusters, including:
determining, based on a parity of a respective cluster that is not adjacent to a boundary with open edges, whether the respective cluster is valid; and
determining that a respective cluster that is adjacent to a boundary with open edges is valid regardless of a parity of the respective cluster;

reconstructing one or more qubit states or syndrome states for respective clusters of the one or more identified clusters based on qubit states or syndrome states adjacent to the respective clusters of the one or more identified clusters; and
storing information identifying the one or more reconstructed qubit states or syndrome states.

2. The method of claim 1 , wherein:
identifying the one or more clusters in the graph state includes at least one of:
identifying one or more clusters associated with qubit loss; and
identifying one or more clusters with one or more Pauli errors.

3. The method of claim 1 , wherein:
determining, based on the parity of the respective cluster that is not adjacent to a boundary with open edges, whether the respective cluster is valid includes determining that the respective cluster is valid in accordance with a determination that the parity of the respective cluster that is not adjacent to a boundary with open edges is even and determining that the respective cluster is invalid in accordance with a determination that the parity of the respective cluster that is not adjacent to a boundary with open edges is odd.

4. The method of claim 1 , wherein:
a particular cluster of the one or more clusters identified at n+1 generation consist of a corresponding cluster of the one or more clusters identified at n generation and at least a portion of qubit states or syndrome states directly connected, in the graph state, to the corresponding cluster of the one or more clusters identified at n generation.

5. The method of claim 1 , further comprising:
generating a data structure that includes a cluster identifier for a respective vertex or a respective edge of the graph state.

6. The method of claim 1 , further comprising:
in accordance with a determination that two or more clusters have one or more connecting qubit states or syndrome states, merging the two or more clusters.

7. The method of claim 1 , further comprising:
at a quantum state detector, detecting quantum states of a second plurality of entangled qubit states that is distinct and separate from the first plurality of entangled qubit states based on the information identifying the one or more reconstructed qubit states or syndrome states.

8. An electronic decoder of a quantum computing system, the electronic decoder comprising:
one or more processors; and
memory storing one or more programs for execution by the one or more processors, the one or more programs including instructions for performing the method of claim 1 .

9. A non-transitory computer readable storage medium storing one or more programs, the one or more programs including instructions, which, when executed by a decoder of a quantum computing system having one or more processors and memory, cause the decoder to perform the method of claim 1 .

10. A method, comprising:
at a decoder of a quantum computing system:
receiving information identifying syndrome values for a first plurality of entangled qubit states represented by a first graph state with a respective edge of the first graph state corresponding to a respective qubit state of the plurality of entangled qubit states;
repeating, for N generations, identifying one or more clusters of at least one of: qubit states and syndrome states in the first graph state until all of the one or more identified clusters are determined to be valid, including increasing a size of a respective cluster each time the identifying operation is performed so that the respective cluster at n+1 generation includes the respective cluster at n generation and at least a portion of qubit states or syndrome states adjacent, in the first graph state, to the respective cluster at n generation;
combining at least a portion of the information identifying the syndrome values for the first plurality of entangled qubit states and information identifying syndrome values for a second plurality of entangled qubit states that are adjacent to the first plurality of entangled qubit states, at least the portion of the first plurality of entangled qubit states and the second plurality of entangled qubit states being collectively represented by a second graph state, the second graph state including at least a portion of the first boundary within a non-boundary region of the second graph state;
repeating identifying one or more clusters of at least one of: qubit states and syndrome states, in the second graph state, until all of the one or more identified clusters are determined to be valid, including identifying, initially, at least a subset of the one or more clusters, in the first graph state, identified at a generation prior to the N generation as at least a subset of the one or more clusters in the second graph state, and increasing a size of a respective cluster each time the identifying operation is performed;
reconstructing one or more qubit states or syndrome states for a respective cluster of the one or more identified clusters based on qubit states or syndrome states adjacent to the respective cluster of the one or more identified clusters; and
storing information identifying the one or more reconstructed qubit states or syndrome states.

11. The method of claim 10 , wherein:
the second graph state has a second boundary that is not included in the first graph state;
the second boundary is away from the first boundary by m vertices; and
repeating identifying one or more clusters in the second graph state includes identifying, initially, the one or more clusters, in the first graph state, identified at N−k generation, k being equal to, or greater than, m.

12. The method of claim 11 , wherein m equals 1.

13. The method of claim 10 , wherein:
the second graph state includes either (i) the first graph state and (ii) the information identifying syndrome values for the second plurality of entangled qubit states, or (iii) a subset, less than all, of the first graph state and (iv) the information identifying syndrome values for the second plurality of entangled qubit states.

14. A method, comprising:
at a decoder of a quantum computing system:
receiving information identifying syndrome values for a plurality of entangled qubit states represented by a graph state with a respective edge of the graph state corresponding to a respective qubit state of the plurality of entangled qubit states;
identifying a first set of multiple clusters of

Assignees

• Psiquantum Corp

Inventors

• Nickerson Naomi
• Delfosse Nicolas

Classifications

• G06N10/00

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

• G06N10/70 Primary

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

• G06F11/10 Primary

  Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's · CPC title