```
import json
import pennylane as qml
import pennylane.numpy as np
dev = qml.device('default.qubit', wires=2)
@qml.qnode(dev)
def circuit1(angles):
"""
A Qnode implementing the circuit shown in the top part of the image
Args:
angles (np.ndarray(float)): A list [theta_1, theta_2] of angle
parameters for the RX and RY gates respectively
Returns:
(np.tensor): The expectation value of the PauliX observable
"""
# Put your code here #
qml.RX(angles[0], wires = 0)
qml.RY(angles[1], wires = 1)
# Return the expectation value
return qml.probs(wires=[0, 1])
@qml.qnode(dev)
def circuit2(angles):
"""
A Qnode implementing the circuit shown in the bottom part of the image
Args:
angles (np.ndarray(float)): A list [theta_1, theta_2] of angle
parameters for the RX and RY gates respectively
Returns:
(np.tensor): The expectation value of the PauliX observable
"""
# Put your code here #
qml.RY(angles[0], wires = 0)
qml.RX(angles[1], wires = 1)
# Return the expectation value
return qml.probs(wires=[0, 1])
def compare_circuits(angles):
"""
Given two angles, compare two circuit outputs that have their order of
operations flipped: RX then RY VERSUS RY then RX.
Args:
angles (np.ndarray(float)): An array of two angles [theta_1, theta_2]
Returns:
(float): The absolute value of the difference between the expectation
values of the circuits.
"""
# Put your code here #
return abs(circuit1(angles) - circuit2(angles))
# Return the required difference in expectation values
# These functions are responsible for testing the solution.
def run(test_case_input: str) -> str:
ins = json.loads(test_case_input)
output = compare_circuits(ins)
return str(output)
def check(solution_output: str, expected_output: str) -> None:
solution_output = json.loads(solution_output)
expected_output = json.loads(expected_output)
assert np.isclose(solution_output, expected_output, rtol=1e-4)
# These are the public test cases
test_cases = [
('[3.79894785, 0.71678115]', '1.177019'),
('[5.88344281, 0.30672784]', '0.023805')
]
# This will run the public test cases locally
for i, (input_, expected_output) in enumerate(test_cases):
print(f"Running test case {i} with input '{input_}'...")
try:
output = run(input_)
except Exception as exc:
print(f"Runtime Error. {exc}")
else:
if message := check(output, expected_output):
print(f"Wrong Answer. Have: '{output}'. Want: '{expected_output}'.")
else:
print("Correct!")
```

```
Test 1 of 2 failed! 🚫
Input: [3.79894785, 0.71678115]
Expected output: 1.177019
Solution output: [0. 0. 0. 0.]
Failure message: Runtime Error: Failed to execute check() function: Expecting ',' delimiter: line 1 column 3 (char 2).
```

I’m facing this error in all challenges.I tried with a different browser, it remains the same. And every challenge shows the same error even if I don’t change anything in the code.