An Example of Non - Attainability of Expected Quantum
نویسنده
چکیده
Braunstein and Caves showed how quantum information can be used to deene a metric for quantum states, relying on attainability of a quantum information bound. We show that the bound is not generally attainable, but that a two-stage procedure of repeated measurements achieves the bound in the limit. We connect to the question of`non-locality without entanglement': can a joint measurement on n independent copies of a quantum system yield more information than separate measurements. Though for small n generalized measurements are more informative, the gain is asymptotically negligible in the pure state, spin-half, examples studied.
منابع مشابه
ua nt - p h / 98 08 00 9 v 1 5 A ug 1 99 8 An Example of Non - Attainability of Expected Quantum Information
Braunstein and Caves showed how quantum information can be used to define a metric for quantum states, relying on attainability of a quantum information bound. We show that the bound is not generally attainable. But a two-stage procedure of repeated measurements achieves the bound in the limit. We connect to the question of whether a generalised measurement on n independent copies of a quantum ...
متن کاملar X iv : q ua nt - p h / 98 08 00 9 v 2 9 F eb 1 99 9 An Example of Non - Attainability of Expected Quantum Information
Braunstein and Caves showed how quantum information can be used to define a metric for quantum states, relying on attainability of a quantum information bound. We show that the bound is not generally attainable, but that a two-stage procedure of repeated measurements achieves the bound in the limit. We connect to the question of 'non-locality without entanglement': can a joint measurement on n ...
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