Generalized measurements by linear elements
Abstract
I give a first characterization of the class of generalized measurements that can be exactly realized on a pair of qudits encoded in indistinguishable particles, by using only linear elements and particle detectors. Two immediate results follow from this characterization. (i) The Schmidt number of each element in the positive operator valued measure cannot exceed the number of initial particles. This rules out any possibility of performing perfect Bell measurements for qudits. (ii) The maximum probability of performing a generalized incomplete Bell measurement is onehalf.
 Publication:

Physical Review A
 Pub Date:
 March 2002
 DOI:
 10.1103/PhysRevA.65.030301
 arXiv:
 arXiv:quantph/0108108
 Bibcode:
 2002PhRvA..65c0301C
 Keywords:

 03.67.a;
 03.67.Hk;
 42.50.p;
 42.25.Hz;
 Quantum information;
 Quantum communication;
 Quantum optics;
 Interference;
 Quantum Physics
 EPrint:
 4 pages. Submitted to Phys. Rev. A