| CPC H04L 9/0852 (2013.01) [G06N 10/70 (2022.01); H04L 9/30 (2013.01)] | 9 Claims |

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1. A classical computer comprising:
processing circuitry:
to, using a first measurement result and a second measurement result, compute a state space probability that is a probability that a quantum computer has not correctly prepared a state space having a first quantum state stored therein, the first quantum state being a quantum state generated by the quantum computer, wherein the first measurement result is a result of measuring the first quantum state by the quantum computer, and the second measurement result is a result of measuring a second quantum state by the quantum computer, the second quantum state being a quantum state after change of the first quantum state caused by the measurement of the first quantum state;
to, using a third measurement result, a fourth measurement result, and the first measurement result, compute a Pauli measurement probability that is a probability that the quantum computer has not correctly performed Pauli Z measurement and Pauli X measurement on a fourth quantum state, wherein the third measurement result is a result of measuring a third quantum state by the quantum computer, the third quantum state being a quantum state after change of the first quantum state caused by the measurement of the first quantum state and different from the second quantum state, and the fourth measurement result is a result of measuring the fourth quantum state by the quantum computer, the fourth quantum state being a quantum state after change of the third quantum state caused by the measurement of the third quantum state;
to, using the first measurement result, the third measurement result, and the fourth measurement result, compute a magic state probability that is a probability that the quantum computer has not generated a magic state of CCZ (Controlled Controlled-Z); and
to, using the state space probability, the Pauli measurement probability, and the magic state probability, compute a degree of approximation between the fourth quantum state and the magic state of CCZ, and measurement accuracies of the Pauli Z measurement and the Pauli X measurement on the fourth quantum state, wherein
the processing circuitry generates a public key and a trapdoor from initial data,
the quantum computer generates the first quantum state based on the public key,
the processing circuitry computes the state space probability, using the first measurement result, the second measurement result, and the public key,
the processing circuitry computes the Pauli measurement probability, using the first measurement result, the third measurement result, the fourth measurement result, the public key, and the trapdoor, and
the processing circuitry computes the magic state probability, using the first measurement result, the third measurement result, the fourth measurement result, the public key, and the trapdoor.
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