Let B₁ := { |H⟩ := |H⟩, |V⟩ := |V⟩ } denote an orthonormal basis in the Hilbert space ℂ². The states |H⟩ and |V⟩ can be identified with the horizontal and vertical polarization of a photon. Let B₂ := { |0⟩ := (|H⟩ + |V⟩)/√2, |1⟩ := (|H⟩ - |V⟩)/√2 } denote a second orthonormal basis in ℂ². These states are identified with the 45° and -45° polarization of a photon. Alice sends photons randomly prepared in one of the four states |H⟩, |V⟩, |0⟩, and |1⟩ to Bob. Bob then randomly chooses a basis B₁ or B₂ to measure the polarization of the photon. All random decisions follow the uniform distribution. Alice and Bob interpret |0⟩ as binary 0 and |1⟩ as binary 1 in the basis B₁. They interpret |0⟩ as binary 0 and |1⟩ as binary 1 in the basis B₂. (i) What is the probability that Bob measures the photon in the state prepared by Alice, i.e., what is the probability that the binary interpretation is identical for Alice and Bob?

Relax