  We derive exceedingly simple practical procedures revealing the quantum
nature of states and measurements by the violation of classical upper bounds on
the statistics of arbitrary measurements. Data analysis is minimum and definite
conclusions are obtained without evaluation of moments, or any other more
sophisticated procedures. These nonclassical tests are independent of other
typical quantum signatures such as sub-Poissonian statistics, quadrature
squeezing, or oscillatory statistics. This approach can be equally well applied
to very diverse situations such as single- and two-mode fields, observables
with continuous and discrete spectra, finite- and infinite-dimensional systems,
and ideal and noisy measurements.
