Entangled quantum states as direction indicators
arXiv:quant-ph/0010085 · doi:10.1103/PhysRevLett.86.4160
Abstract
We consider the use of N spin-1/2 particles for indicating a direction in space. If N>2, their optimal state is entangled. For large N, the mean square error decreases as N^{-2} (rather than N^{-1} for parallel spins).
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