Master

.gitignore

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-.DS_Store
+.DS_Store

.vscode/settings.json

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+{
+    "python-envs.defaultEnvManager": "ms-python.python:conda",
+    "python-envs.defaultPackageManager": "ms-python.python:conda"
+}

Comparison.py

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+from qiskit import QuantumCircuit, transpile
+from qiskit.transpiler import CouplingMap
+from qiskit.quantum_info import Statevector, state_fidelity
+from qiskit_aer import AerSimulator
+from qiskit_aer.noise import NoiseModel, depolarizing_error
+
+# -------------------------------------------------
+# 1. Build GHZ
+# -------------------------------------------------
+def build_ghz_circuit(n_qubits: int = 6) -> QuantumCircuit:
+    qc = QuantumCircuit(n_qubits)
+    qc.h(0)
+    for i in range(n_qubits - 1):
+        qc.cx(i, i + 1)
+    return qc
+
+
+# -------------------------------------------------
+# 2. Same "platform style": fixed basis + fixed coupling map
+#    Use a 6-qubit connected chain, so memory stays small.
+# -------------------------------------------------
+def get_platform_spec(n_qubits: int):
+    basis_gates = ["rz", "sx", "x", "ecr"]
+
+    edges = []
+    for i in range(n_qubits - 1):
+        edges.append([i, i + 1])
+        edges.append([i + 1, i])
+
+    coupling = CouplingMap(edges)
+    return basis_gates, coupling
+
+
+# -------------------------------------------------
+# 3. Build two noise models: low / high
+# -------------------------------------------------
+def make_noise_model(p1: float, p2: float) -> NoiseModel:
+    noise_model = NoiseModel()
+
+    err_1q = depolarizing_error(p1, 1)
+    err_2q = depolarizing_error(p2, 2)
+
+    for gate in ["rz", "sx", "x"]:
+        noise_model.add_all_qubit_quantum_error(err_1q, gate)
+
+    noise_model.add_all_qubit_quantum_error(err_2q, ["ecr"])
+
+    return noise_model
+
+
+# -------------------------------------------------
+# 4. Noisy density-matrix simulation
+# -------------------------------------------------
+def simulate_density_matrix(circuit: QuantumCircuit, noise_model: NoiseModel):
+    sim = AerSimulator(method="density_matrix", noise_model=noise_model)
+
+    circ = circuit.copy()
+    circ.save_density_matrix()
+
+    result = sim.run(circ).result()
+    rho = result.data(0)["density_matrix"]
+    return rho
+
+
+# -------------------------------------------------
+# 5. Main
+# -------------------------------------------------
+def main():
+    n_qubits = 10
+    ghz = build_ghz_circuit(n_qubits)
+
+    basis_gates, coupling = get_platform_spec(n_qubits)
+
+    ghz_t = transpile(
+        ghz,
+        basis_gates=basis_gates,
+        coupling_map=coupling,
+        optimization_level=3,
+        seed_transpiler=42,
+    )
+
+    # Ideal target
+    ideal_state = Statevector.from_instruction(ghz_t)
+
+    # Low-noise version
+    noise_low = make_noise_model(
+        p1=0.0020,
+        p2=0.020,
+    )
+
+    # High-noise version
+    noise_high = make_noise_model(
+        p1=0.0035,
+        p2=0.020,
+    )
+
+    rho_low = simulate_density_matrix(ghz_t, noise_low)
+    rho_high = simulate_density_matrix(ghz_t, noise_high)
+
+    fid_low = state_fidelity(ideal_state, rho_low)
+    fid_high = state_fidelity(ideal_state, rho_high)
+
+    print("=== Transpiled GHZ circuit ===")
+    print(ghz_t)
+    print()
+
+    ops = ghz_t.count_ops()
+
+    total_gates = sum(ops.values())
+    two_q_gates = sum(v for k, v in ops.items() if k in ["cx", "cz", "swap", "ecr"])
+    one_q_gates = total_gates - two_q_gates
+
+    print("num_qubits :", ghz_t.num_qubits)
+    print("depth      :", ghz_t.depth())
+    print("1Q gates   :", one_q_gates)
+    print("2Q gates   :", two_q_gates)
+    print("total gates:", total_gates)
+    print()
+
+    print("=== Fidelity comparison ===")
+    print(f"Low-noise fidelity  : {fid_low:.6f}")
+    print(f"High-noise fidelity : {fid_high:.6f}")
+    print(f"Δ Fidelity          : {fid_low - fid_high:.6f}")
+
+
+if __name__ == "__main__":
+    main()