Complete product-state contact set and optimality of the canonical three-qubit Shifts witness

Bing-Dong Wan, Yu-Chen Guo

For the three-qubit Shifts unextendible product basis (UPB), the minimum product-state expectation value ${\lambda }_{\mathrm{Shifts}}=1-3\sqrt{6}/8$ of the UPB projector is known, and four a…