  We search a simplest and minimal way to determine whether a given quantum
system is entangled or separable. For this end, we propose binary correlation
measurements in which restricted knowledge of only zero or non-zero
correlations is available. We consider the concrete investigation on a pure
state for two particles, each particle having two basis states (the 2x2
system). We show that, even with this limited information from the binary
correlation measurements, we can still reach the known minimum of three
measurements for entanglement detection. We next consider the comparable
problem applied to the mixed density matrix. The mixed quantum case appears to
require more detailed information, which we illustrate by studying the concrete
example of the Werner density matrix.
