Optical-state truncation and teleportation of qudits by conditional eight-port interferometry

Quantum scissors device of Pegg et al. (1998 Phys. Rev. Lett. 81, 1604) enables truncation of the Fock-state expansion of an input optical field to qubit and qutrit (three-dimensional) states only. Here, a generalized scissors device is proposed using an eight-port optical interferometer. Upon post-selection based on photon counting results, the interferometer implements generation and teleportation of qudit (d-dimensional) states by truncation of an input field at the (d-1)th term of its Fock-state expansion up to d=6. Examples of selective truncations, which can be interpreted as a Fock-state filtering and hole burning in the Fock space of an input optical field, are discussed. Deterioration of the truncation due to imperfect photon counting is discussed including inefficiency, dark counts and realistic photon-number resolutions of photodetectors.