fix(quilatom): format complex params with nonzero real and unit imaginary part

[devteamaegis]

What's broken

format_parameter raises ValueError on a complex number whose imaginary part is exactly +1/-1 while the real part is nonzero (e.g. 2+1j). It's reachable through the non-deprecated noise path _create_kraus_pragmas, which serializes Kraus-operator entries into a PRAGMA ADD-KRAUS string — and Kraus operators commonly have entries like 2+1j:

import numpy as np
from pyquil.noise import _create_kraus_pragmas
_create_kraus_pragmas("MYGATE", [0], [np.array([[2+1j, 0],[0, 1]])])
# ValueError: Invalid complex number: (2+1j)

Why it happens

The i == 1 / i == -1 branches assumed the real part must be ~0 and raised otherwise. The np.isclose(r, 0) check is only meant to drop tiny floating residuals; when the real part is genuinely nonzero it should append +i/-i to the real part, like every other complex value.

Fix

When the real part is nonzero, append +i/-i instead of raising. Output round-trips through pyQuil's own parser (2.0+i).

Test

Extended test_format_parameter with 2+1j, 2-1j, -3+1j; the existing 1e-15±1j → ±"i" cases still pass, and test_noise.py (the Kraus path) stays green.

[windsurf-bot]

Looks good to me 🤙

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