Experimental realization of an approximate transpose operation for qutrit systems using a structural physical approximation

摘要

Although important for detecting entanglement, the transpose operation cannot be directly realized in laboratorynbecause it is a nonphysical operation. It is, however, possible to find an approximate transpose operation usingnthe method known as the structural physical approximation (SPA); recently, SPA-based implementations of thentranspose and partial transpose have been demonstrated for a single-qubit [Phys. Rev. A 83, 020301(R) (2011)]nand an entangled two-qubit system [Phys. Rev. Lett. 107, 160401 (2011)]. In this work, we expand SPA-transposento a three-dimensional quantum system: a qutrit. The photonic qutrit state is encoded in the polarization, and pathndegrees of freedom of a single-photon and the SPA-transpose operation, which is based on measurement andnpreparation of quantum states, is implemented with linear optics. Our work paves the way toward entanglementndetection for higher-dimensional quantum systems.