Using linear optical elements we have demonstrated a deterministic Controlled-NOT gate for a quantum logic protocol that uses the polarization and momentum degrees of freedom of a single photon as the control and target qubits.
We demonstrate a robust implementation of a deterministic linear-optical controlled-not gate for single-photon two-qubit quantum logic. A polarization Sagnac interferometer with an embedded 45 degrees -oriented dove prism is used to enable the polarization control qubit to act on the momentum (spatial) target qubit of the same photon. The optical controlled-not gate requires no active stabilization because the two spatial modes share a common path, and it is used to entangle the polarization and momentum qubits.
Quantum controlled-logic gates, including controlled not gate and Toffoli gate, play critical roles in lots of quantum information processing schemes. We design and experimentally demonstrate deterministic Toffoli gate by utilizing orbital-angular-momentum and polarization degrees of freedom of a single photon. In addition, we generate Bell states by using the controlled not gate. The effective conversion rate of the Toffoli gate in our experiment is $(95.1\ifmmode\pm\else\textpm\fi{}3.2)%$. Furthermore, our experimental setup does not require any auxiliary photons and probabilistic postselections.