The set of these states allowed by consistent theories is measure zero within a larger set that Cumrun Vafa called the “swampland.” This state is Poincaré-invariant, cyclic, (10[1])and unique as a consequence of the Wightman axioms. Sidney Coleman proposed a mechanism in Kaluza–Klein theories where the decay of a metastable one of these states is caused by bubble nucleation. In the Fock space construction, repeatedly applying the creation operator to this state generates an n-particle Fock state. The Casimir effect arises from a (10[1])non-zero value (10[1])of this state’s expectation value. (10[1])The self-energy of the photon causes this state’s namesake “polarization.” Virtual particles spontaneously emerge and annihilate from this state. (-5[1])For 10 points, name this lowest quantum state consisting of empty space. ■END■ (10[2])