Granted Patent B2

US 12,536,462 · App. 18/525,914 · Granted Jan 27, 2026

Inventors: Jeongseok Ha (Daejeon, KR); Hyunwoo Jung (Daejeon, KR)

Assignee: Korea Advanced Institute of Science and Technology

G06N10/70

Abstract

Claims (36)

1 . A method for determining a recovery operator using a topological structure of a rotated surface code, the method comprising:

determining a reliability of n qubits included in the rotated surface code using a belief propagation decoding algorithm, wherein n is an integer of 2 or more;

setting at least one subset for the n qubits based on the reliability of the n qubits; and

determining the recovery operator using the at least one subset,

wherein the setting of the at least one subset includes:

setting a fix set containing k qubits in an ascending order of values derived through computations on the reliability of the n qubits, wherein k is an integer greater than or equal to 1 and less than n, the k qubits being selected among the n qubits and having a lowest reliability based on a log-likelihood ratio; and

setting a reset set containing n−k qubits, the n−k qubits being selected among the n qubits and not included in the fix set.

2 . The method of claim 1 , wherein the determining of the reliability of the n qubits includes determining the reliability based on the log-likelihood ratio derived through the belief propagation decoding algorithm.

3 . The method of claim 1 , wherein the setting of the fix set includes setting the fix set such that the recovery operator determined from the n-k qubits included in the reset set has a same logical state with reference to the topological structure of the surface code.

4 . The method of claim 1 , wherein the determining of the recovery operator includes determining the recovery operator based on the log-likelihood ratio derived for the k qubits in the case of the fix set.

5 . The method of claim 1 , wherein the determining of the recovery operator includes determining the recovery operator corresponding to a syndrome using a pure error determined for the n-k qubits in the case of the reset set.

6 . An apparatus for determining a recovery operator using a topological structure of a rotated surface code, the apparatus comprising:

a memory in which a recovery operator determination program is stored; and

a processor configured to load the recovery operator determination program from the memory and to execute the recovery operator determination program,

wherein the processor is configured to:

determine a reliability of n qubits included in the rotated surface code using a belief propagation decoding algorithm, wherein n is an integer of 2 or more:

set at least one subset for the n qubits based on the reliability of the n qubits; and

determine the recovery operator using the at least one subset,

wherein the processor is configured to:

set a fix set containing k qubits in an ascending order of values derived through computations on the reliability of the n qubits, wherein k is an integer greater than or equal to 1 and less than n, the k qubits being selected among the n qubits and having a lowest reliability based on a log-likelihood ratio; and

set a reset set containing n−k qubits, the n−k qubits being selected among the n qubits and not included in the fix set.

7 . The apparatus of claim 6 , wherein the processor is configured to determine the reliability based on the log-likelihood ratio derived through the belief propagation decoding algorithm.

8 . The apparatus of claim 6 , wherein the processor is configured to set the fix set such that the recovery operator determined from the n−k qubits included in the reset set has a same logical state with reference to the topological structure of the surface code.

9 . The apparatus of claim 6 , wherein the processor is configured to determine the recovery operator based on the log-likelihood ratio derived for the k qubits in the case of the fix set.

10 . The apparatus of claim 6 , wherein the processor is configured to determine the recovery operator corresponding to a syndrome using a pure error determined for the n−k qubits in the case of the reset set.

11 . A non-transitory computer-readable storage medium storing a computer program, the computer program including instructions causing a processor to perform, when executed by the processor, a method of determining a recovery operator using a topological structure of a rotated surface code, the method comprising:

determining a reliability of n qubits included in the rotated surface code using a belief propagation decoding algorithm, wherein n is an integer of 2 or more;

setting at least one subset for the n qubits based on the reliability of the n qubits; and

determining the recovery operator using the at least one subset,

wherein the setting of the at least one subset includes:

setting a fix set containing k qubits in an ascending order of values derived through computations on the reliability of the n qubits, wherein k is an integer greater than or equal to 1 and less than n, the k qubits being selected among the n qubits and having a lowest reliability based on a log-likelihood ratio; and

setting a reset set containing n−k qubits, the n−k qubits being selected among the n qubits and not included in the fix set.

12 . The non-transitory computer-readable storage medium of claim 11 , wherein the determining of the reliability of the n qubits includes determining the reliability based on the log-likelihood ratio derived through the belief propagation decoding algorithm.

13 . The non-transitory computer-readable storage medium of claim 11 , wherein the setting of the fix set includes setting the fix set such that the recovery operator determined from the n−k qubits included in the reset set has a same logical state with reference to the topological structure of the surface code.

14 . The non-transitory computer-readable storage medium of claim 11 , wherein the determining of the recovery operator includes determining the recovery operator based on the log-likelihood ratio derived for the k qubits in the case of the fix set.

15 . The non-transitory computer-readable storage medium of claim 11 , wherein the determining of the recovery operator includes determining the recovery operator corresponding to a syndrome using a pure error determined for the n−k qubits in the case of the reset set.

Assignments (1)

Priority Claims (1)

Continuity (1)

References Cited (9)