Ascertaining the values of sigma x, sigma y, and sigma z of a polarization qubit.
In the 1987 spin-retrodiction puzzle of Vaidman, Aharonov, and Albert one is challenged to ascertain the values of sigma(x), sigma(y), and sigma(z) of a spin-1/2 particle by utilizing entanglement. We report the experimental realization of a quantum-optical version in which the outcome of an intermediate polarization projection is inferred by exploiting single-photon two-qubit quantum gates. The experimental success probability is consistently above the 90.2% threshold of the optimal one-qubit strategy, with an average success probability of 95.6%.
Schulz
Oliver
O
Sektion Physik, Universität München, Schellingstrasse 4, 80799 München, Germany.
Steinhübl
Ruprecht
R
Weber
Markus
M
Englert
Berthold-Georg
BG
Kurtsiefer
Christian
C
Weinfurter
Harald
H