Quantum simulation device and operating method of quantum simulation device

1 . An operating method of a surface code-based quantum simulation device that includes physical qubit storage, the method comprising:

storing initialized entanglement states of logical qubits corresponding to different distances;

receiving a surface code-based initialization request corresponding to a specific distance; and

storing an initialized entanglement state of a logical qubit corresponding to the specific distance from among the initialized entanglement states of the logical qubits corresponding to the different distances in the physical qubit storage,

wherein the storing of the initialized entanglement state of the logical qubit corresponding to the specific distance in the physical qubit storage includes:

storing states indicating the initialized entanglement state of the logical qubit in the physical qubit storage,

wherein the states are 2 R , and

wherein the “R” corresponds to a value obtained by dividing a value, which is obtained by subtracting 1 from the number of physical qubits indicating the logical qubit, by 4.

2 . The method of claim 1 , wherein the physical qubits include physical qubits corresponding to X stabilizers, physical qubits corresponding to Z stabilizers, and physical qubits corresponding to data qubits.

3 . The method of claim 1 , wherein the storing of the initialized entanglement state of the logical qubit corresponding to the specific distance in the physical qubit storage includes:

storing one state among states indicating the initialized entanglement state of the logical qubit in the physical qubit storage.

4 . The method of claim 1 , further comprising:

measuring a syndrome for a state of a logical qubit stored in the physical qubit storage,

wherein addition of states indicating the state of the logical qubit is prevented in a process of measuring the syndrome.

5 . The method of claim 4 , wherein the measuring of the syndrome includes:

determining a product of eigenvalues of neighboring data qubits, for each of 4 neighbor X stabilizers; and

determining whether a measurement value of each of the 4 neighbor X stabilizers is |0>, in response to that the product of the eigenvalues of the neighboring data qubits is 1.

6 . The method of claim 5 , wherein the measuring of the syndrome further includes:

determining whether the measurement value of each of the 4 neighbor X stabilizers is |1>, in response to that the product of the eigenvalues of the neighboring data qubits is −1.

7 . The method of claim 5 , wherein the eigenvalues of the neighboring data qubits are measured on a Z-axis basis.

8 . The method of claim 4 , wherein the measuring of the syndrome further includes:

determining a product of eigenvalues of neighboring data qubits, for each of 2 neighbor X stabilizers; and

determining whether a measurement value of each of the 2 neighbor X stabilizers is |0>, in response to that the product of the eigenvalues of the neighboring data qubits is 1.

9 . The method of claim 8 , wherein the measuring of the syndrome further includes:

determining whether the measurement value of each of the 2 neighbor X stabilizers is |1>, in response to that the product of the eigenvalues of the neighboring data qubits is −1.

10 . The method of claim 4 , wherein the measuring of the syndrome includes:

determining a product of eigenvalues of neighboring data qubits, for each of 4 neighbor Z stabilizers; and

determining whether a measurement value of each of the 4 neighbor Z stabilizers is |0>, in response to that the product of the eigenvalues of the neighboring data qubits is 1.

11 . The method of claim 10 , wherein the measuring of the syndrome further includes:

determining whether the measurement value of each of the 4 neighbor Z stabilizers is |1>, in response to that the product of the eigenvalues of the neighboring data qubits is −1.

12 . The method of claim 10 , wherein the eigenvalues of the neighboring data qubits are measured on an X-axis basis.

13 . The method of claim 4 , wherein the measuring of the syndrome includes:

determining a product of eigenvalues of neighboring data qubits, for each of 2 neighbor Z stabilizers; and

determining whether a measurement value of each of the 2 neighbor Z stabilizers is |0>, in response to that the product of the eigenvalues of the neighboring data qubits is 1.

14 . The method of claim 13 , wherein the measuring of the syndrome further includes:

determining whether the measurement value of each of the 2 neighbor Z stabilizers is |1>, in response to that the product of the eigenvalues of the neighboring data qubits is −1.

15 . An operating method of a quantum simulation device which simulates a logical qubit including data qubits and stabilizers, the method comprising:

measuring, by the quantum simulation device, eigenvalues of 4 neighboring data qubits, for each of 4 neighbor stabilizers among the stabilizers;

determining, by the quantum simulation device, a measurement value of each of the 4 neighbor stabilizers depending on a product of the eigenvalues of the 4 neighboring data qubits;

measuring, by the quantum simulation device, eigenvalues of 2 neighboring data qubits, for each of 2 neighbor stabilizers among the stabilizers; and

determining, by the quantum simulation device, a measurement value of each of the 2 neighbor stabilizers depending on a product of the eigenvalues of the 2 neighboring data qubits,

wherein the measurement value of each of the 4 neighbor stabilizers and the measurement value of each of the 2 neighbor stabilizers are a syndrome of the logical qubit, and wherein states indicating the logical qubit are prevented from being added during generating the syndrome of the logical qubit, and

wherein the operating method further comprises:

determining the product of the eigenvalues of the 4 neighboring data qubits; and

determining whether the measurement value of each of the 4 neighbor stabilizers is |0>, in response to that the product of the eigenvalues of the 4 neighboring data qubits is 1.