Equation 98 · A Reference Frame Becomes Classical by Publishing Its Orientation
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Classical limit. As j grows, a spin-coherent direction becomes sharper. As N grows, more probes become available. It is tempting to write “therefore redundancy diverges,” but back-action, finite coupling, loss, and fragment-size requirements decide the rate. The required limit is more modest: under a scaling that keeps the physical interaction and total disturbance controlled, the quantum calculation should approach the corresponding classical direction-estimation model. Bartlett and colleagues’ finite-frame results and Poulin and Yard’s dynamical analysis provide benchmarks for how use and degradation can scale [ 4 , 3 ] .
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