Let the component of the Hamiltonian that represent the measurement device for an entangled two level system (e.g. Photon polarisation) be H_m and let the set $S=\{++,+-,-+,++\}$. Then $$ H_m=\sum_{\lambda \in S}a_{\lambda++}\lvert\lambda\rangle\langle++\rvert+a_{\lambda+-}\lvert\lambda\rangle\langle+-\rvert+a_{\lambda-+}\lvert\lambda\rangle\langle-+\rvert+a_{\lambda--}\lvert\lambda \rangle \langle--\rvert$$

Now consider an entangled state $\lvert\Psi\rangle=\frac{1}{\sqrt{2}}(\lvert++\rangle+\lvert--\rangle)$. When the measurement is made, the state evolved as follows $$H_m\lvert\Psi\ran…