Physics · Quantum Mechanics

A spin-1/2 system is prepared in the initial state |φ⟩ = √32|↑⟩ + 12|↓⟩, where |↑⟩ and |↓⟩ are eigenstates of Sz with eigenvalues +ℏ2 and -&span style='display:inline-block;vertical-align:middle;text-align:center;line-height:1.1'>ℏ2 respectively. A measurement of Sz is performed first, followed by a measurement of Sx on the system. What is the probability that the measurement of Sx yields a value of +ℏ2?