Add tests for toqito/channel_metrics/channel_fidelity.py : 82-97, 79->82

[purva-thakre]

• L82-97: Fixed by 523bf11
• L79-82: Fixed by 9679322

Failing tests (if commented out)

FAILED test_channel_fidelity.py::test_channel_fidelity_same_channel - TypeError: Failed to convert argument 'x' of partial_trace to a PICOS constant.
FAILED test_channel_fidelity.py::test_channel_fidelity_different_channel - TypeError: Failed to convert argument 'x' of partial_trace to a PICOS constant.

toqito/tests/test_channel_metrics/test_channel_fidelity.py

Lines 7 to 18 in a929bb0

	# def test_channel_fidelity_same_channel():
	# """The fidelity of identical channels should yield 1."""
	# choi_1 = dephasing(4)
	# choi_2 = dephasing(4)
	# np.testing.assert_equal(np.isclose(channel_fidelity(choi_1, choi_2), 1, atol=1e-3), True)
	# def test_channel_fidelity_different_channel():
	# """Calculate the channel fidelity of different channels."""
	# choi_1 = dephasing(4)
	# choi_2 = depolarizing(4)
	# np.testing.assert_equal(np.isclose(channel_fidelity(choi_1, choi_2), 1 / 2, atol=1e-3), True)