Total spin eigenstates can be used to intrinsically encode a direction, which can later be decoded by means of a quantum measurement. We study the optimal strategy that can be adopted if, as is likely in practical applications, only product states of N spins are available. We obtain the asymptotic behavior of the average fidelity, which provides a proof that the optimal states must be entangled. We also give a prescription for constructing finite measurements for general encoding eigenstates. © 2001 The American Physical Society.
|Journal||Physical Review A - Atomic, Molecular, and Optical Physics|
|Publication status||Published - 1 Jan 2001|