= Equatorial qubit measurement
{title2=$|\alpha_s\rangle=(|0\rangle+(-1)^s e^{-i\alpha}|1\rangle)/\sqrt2$}
The orthonormal <quantum states> $|\alpha_s\rangle=(|0\rangle+(-1)^se^{-i\alpha}|1\rangle)/\sqrt2$, $s=0,1$, define an equatorial <projective measurement>. The measured <observable> is $\cos\alpha\,X-\sin\alpha\,Y$, with <eigenvalue> $(-1)^s$. Thus $\alpha=0$ measures $X$, and $\alpha=\pi/2$ measures $-Y$ with these outcome labels. The sign convention matters when comparing different definitions of equatorial bases.
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