Explicit product ensembles for separable quantum states
Rüdiger Schack, Carlton M. Caves · Journal of Modern Optics · 2000
We present a general method for constructing pure-product-state representations for density operators of N quantum bits. If such a representation has non-negative expansion coefficients, it provides an explicit separable ensemble for the density operator. We derive the condition for separability of a mixture of the Greenberger—Horne—Zeilinger state with the maximally mixed state.