Document matrices for parity gates #3199
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vtomole
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Fixes quantumlib#2806. This is covered by tests, but I ran these checks to be sure: ``` In [1]: import cirq, numpy as np In [2]: def mxx(t): ...: f = np.e**(1j*np.pi*t/2) ...: c = f * np.cos(np.pi*t/2) ...: s = -1j * f * np.sin(np.pi*t/2) ...: return np.array([[c, 0, 0, s], [0, c, s, 0], [0, s, c, 0], [s, 0, 0, c]]) ...: In [3]: def myy(t): ...: f = np.e**(1j*np.pi*t/2) ...: c = f * np.cos(np.pi*t/2) ...: s = -1j * f * np.sin(np.pi*t/2) ...: return np.array([[c, 0, 0, -s], [0, c, s, 0], [0, s, c, 0], [-s, 0, 0, c]]) ...: In [4]: np.allclose(cirq.unitary(cirq.XX**0.1), mxx(0.1)) Out[4]: True In [5]: np.allclose(cirq.unitary(cirq.YY**0.1), myy(0.1)) Out[5]: True ``` NB: Global phase factors complicate documentation. I think we should prefer SU(n) gates (over trying to force one eigenvalue onto the real axis).
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Fixes #2806.
This is covered by tests, but I ran these checks to be sure:
NB: Global phase factors complicate documentation. I think we should prefer SU(n) gates (over trying to force one eigenvalue onto the real axis).