We report an experimental demonstration of entangling two separable photonic ququarts using linear optical elements. Each ququart is implemented by using the dichotomic spatial and polarization modes of a single photon. By interfering two independent ququarts at a polarizing beam splitter, we experimentally generate entangled ququarts.
DOI:https://doi.org/10.1103/PhysRevA.90.063830
©2014 American Physical Society
Scheme for (a) preparation and (b) measurement of a single-photon ququart. and ( and ) are spatial modes in preparation (measurement). () refers to the relative phase between and ( and ). HWP: half-wave plate, PBS: polarizing beam splitter, M: mirror, WPs: half- and quarter-wave plates, BS: beam splitter, Pol.: polarizer, and D: single-photon detector. (c) The entangling operation of two single-photon ququarts using a PBS. The PBS has input ports and , each subdividing into and , and output ports and , each into and . Two separable ququarts enter the PBS via different input ports. When each ququart exits through different output ports, the resultant ququarts become entangled.
Reuse & PermissionsExperiment setup. (a) SPDC process for a photon pair generation, (b) preparation of two independent single-photon ququarts, (c) entangling operation, and (d) analysis of the generated state using quantum state tomography. FPC: fiber polarization controller.
Reuse & Permissions(a) The theoretically expected and (b) the experimentally reconstructed density matrices of Eq. (9). The calculated fidelity is , negativity is , and the purity is . The axis represents 16 orthonormal basis states of two ququarts in an increasing order: , , .
Reuse & Permissions(a) The theoretically expected and (b) the experimentally reconstructed density matrices of Eq. (11). The calculated fidelity is , negativity is , and the purity is .
Reuse & Permissions
