= Entanglement-assisted nondemolition parity measurement
{title2=$K_{uv}=2^{-1/2}P_{u\oplus v}$}
Share a <Bell state> meter pair, apply local system-to-meter <CNOT gates>, and measure each meter in the computational basis. The parity of the local meter records measures system $Z_AZ_B$ while preserving all coherence within either parity sector. The complete tuple of local records has <Kraus operator> $P_{u\oplus v}/\sqrt2$. Each local record is uniform, and the nonlocal result requires <local operations and classical communication> to compare records. A local <Hadamard gate> conjugation supplies the corresponding $X_AX_B$ measurement.
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