title: Entangled quantum states as direction indicators.
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).
authors.affiliation: Department of Physics, Technion-Israel Institute of Technology, 32000 Haifa, Israel.
authors.forename: A
authors.initials: A
authors.lastname: Peres
authors.forename: P F
authors.initials: PF
authors.lastname: Scudo