= Heralded remote preparation of an arbitrary qubit
{title2=$p_{\mathrm{success}}=1/2$}
For a target <pure state> $|\psi\rangle$ of a <qubit>, choose its orthogonal complement so that
$$
|\Psi^-\rangle=\frac{|\psi\rangle|\psi^\perp\rangle-|\psi^\perp\rangle|\psi\rangle}{\sqrt2}.
$$
Measuring the sender's half of this <singlet state> in that basis leaves the receiver in $|\psi\rangle$ when the sender obtains $|\psi^\perp\rangle$. The outcome has <probability> one half. One classical success flag heralds the exact preparation without conveying the target's classical description.
// Target: quantum-theory.bigb
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