|q⟩ Bad Qubits

← Question Bank

Multiple choice
A pure qubit ∣ψ⟩=cos⁡(θ/2)∣0⟩+sin⁡(θ/2)∣1⟩|\psi\rangle = \cos(\theta/2)|0\rangle + \sin(\theta/2)|1\rangle with θ=π/3\theta = \pi/3. Its density operator is ρ=∣ψ⟩⟨ψ∣\rho = |\psi\rangle\langle\psi|. What is the diagonal element ρ[0][0]=⟨0∣ρ∣0⟩\rho[0][0] = \langle 0|\rho|0\rangle?