qiskitで量子もつれ その3

概要

量子もつれが、分からないので、copilotに聞いてみた。
chshの不等式の破れを実験したい。

参考にしたページ

サンプルコード

from qiskit import QuantumCircuit
from qiskit_aer import AerSimulator
import numpy as np

def make_bell_state(qubits, n = 16):
	qc = QuantumCircuit(n, 2)
	qc.x(qubits[0])
	qc.h(qubits[0])
	qc.x(qubits[1])
	qc.cx(qubits[0], qubits[1])
	qc.z(qubits[1])
	return qc

def E(shots, count):
	cs = [count[i + j] if i + j in count else 0 for i in ["0", "1"] for j in ["0", "1"]]
	return (cs[0] + cs[3] - cs[1] - cs[2]) / shots

def real_chsh(theta, qubits, shots = 1024, n = 20):
	qcs = [make_bell_state(qubits, n) for _ in range(4)]
	counts = []
	for i in range(4):
		if i >= 2:
			qcs[i].h(qubits[0])
		qcs[i].ry(-theta, qubits[1]) if i % 2 else qcs[i].ry(-theta - np.pi / 2, qubits[1])
		qcs[i].measure(qubits, [0, 1])
		backend = AerSimulator()
		job = backend.run([qcs[i]], shots = shots)
		counts.append(job.result().get_counts())
	return E(shots, counts[2]) + E(shots, counts[3]) + E(shots, counts[0]) - E(shots, counts[1])

theta = np.pi / 4
shots = 1024
n = 20
print("correlation of [0, 1] by simulation:", real_chsh(theta, [0, 1], shots, n))
print("correlation of [0,12] by simulation:", real_chsh(theta, [0, 12], shots, n))
print("correlation of [0,19] by simulation:", real_chsh(theta, [0, 19], shots, n))

実行結果

$ python3 test8.py
correlation of [0, 1] by simulation: 2.865234375
correlation of [0,12] by simulation: 2.841796875
correlation of [0,19] by simulation: 2.76953125

$ python3 test8.py
correlation of [0, 1] by simulation: 2.857421875
correlation of [0,12] by simulation: 2.833984375
correlation of [0,19] by simulation: 2.82421875

以上。