We present a scheme for a projective measurement of the parity operator Pz=∏i=1Nσz(i) of N-qubits. Our protocol uses a single ancillary qubit, or a probe qubit, and involves manipulations of the total spin of the N qubits without requiring individual addressing. We illustrate our protocol in terms of an experimental implementation with atomic ions in a two-zone linear Paul trap, and further discuss its extensions to several more general cases.
@article{arxiv.quant-ph/0508048,
title = {Measuring the parity of an $N$-qubit state},
author = {B. Zeng and D. L. Zhou and L. You},
journal= {arXiv preprint arXiv:quant-ph/0508048},
year = {2009}
}