  Heisenberg uncertainty relation in quantum mechanics sets the limit on the
measurement precision of non-commuting observables, which prevents us from
measuring them accurately at the same time. In some applications, however, the
information are embedded in two or more non-commuting observables. On the other
hand, quantum entanglement allows us to infer through Einstein-Podolsky-Rosen
correlations two conjugate observables with precision better than what is
allowed by Heisenberg uncertainty relation. With the help of the newly
developed SU(1,1) interferometer, we implement a scheme to measure jointly
information encoded in multiple non-commuting observables of an optical field
with a signal-to-noise ratio improvement of about 20 % over the standard
quantum limit on all measured quantities simultaneously. This scheme can be
generalized to the joint measurement of information in arbitrary number of
non-commuting observables.
