Linear optical CNOT gate with orbital angular momentum and polarization

It is well established in the theory of quantum computation that the controlled-NOT (CNOT) gate is a fundamental element in the construction of a quantum computer. Here, we propose and experimentally demonstrate within a classical light framework that a Mach–Zehnder interferometer composed of polarized beam splitters and a pentaprism in the place of one of the mirrors works as a linear optical quantum CNOT gate. To perform the information processing, the polarization and orbital angular momentum of light act as the control and target qubits, respectively. The readout process is simple, requiring only a linear polarizer and a triangular diffractive aperture prior to detection. The viability and stability of our experiment suggest that the present proposal is a valuable candidate for future implementations in optical quantum computation protocols.