Quantifying spin-momentum correlation in single-particle quantum states using non-linear entanglement witnesses

We present a unifying approach to the quantification of spin-momentum correlation of single spin half and one particle by using the Non-Linear entanglement witnesses (NLEWs) which have been constructed based on convex optimization method. Likewise, we show that for quantum mixed states which are made by means of two types of degrees of freedom spin and momentum, the effect of the Lorentz transformation is to decrease both the amount and the region of entanglement.