Postulates of Quantum Mechanics Postulates 2:The evolution of a closed quantum system is described by a unitary transformation.That is,if the state of the system at time t ist),there exists a unitary Utt's.t.=U) Postulates 2':The evolution of a closed quantum system is described by a unitary transformation.That is,if the state of the system at time t is pt,there exists a uitary Us.t.P=UPUPostulates of Quantum Mechanics • Postulates 2: The evolution of a closed quantum system is described by a unitary transformation. That is, if the state of the system at time 𝑡 is |𝜓𝑡 ⟩, there exists a unitary 𝑈𝑡,𝑡 ′ s.t. 𝜓𝑡 ′ = 𝑈𝑡,𝑡 ′ 𝜓𝑡 • Postulates 2’: The evolution of a closed quantum system is described by a unitary transformation. That is, if the state of the system at time 𝑡 is 𝜌𝑡 , there exists a unitary 𝑈𝑡,𝑡 ′ s.t. 𝜌𝑡 ′ = 𝑈𝑡,𝑡 ′𝜌𝑡𝑈𝑡,𝑡 ′ †