Systems that lack this property may have eigenmode crossings at exceptional points, which have been observed in microwave cavities. Bender and Boettcher proved that PT-symmetric systems have a “pseudo” form of this property, a fact used to create “cloaking” gratings and invisible sensors. Many open quantum systems with controlled dissipation can be described by an effective Hamiltonian that lacks this property, breaking probability conservation. (-5[1])Any two-level Hamiltonian with this property can be expressed as a superposition of the identity matrix and the (*) Pauli matrices. If an operator (10[1])A has this property, then the exponential of i times A is unitary. Observables in quantum mechanics (10[1])are assumed to have this (-5[1])property, (10[1])which implies that eigenvalues are real (10[1])and eigenvectors are orthogonal. (-5[1])For 10 points, name this property possessed by a matrix that equals its conjugate (10[1])transpose. ■END■ (10[3]0[1])