We discuss a novel method of efficiently producing multi-photon states using repeated spontaneous parametric downconversion. By attempting downconversion several times, we can pseudo-deterministically add photons to a mode, producing various several-photon states.
We discuss a novel method of efficiently producing multiphoton states using repeated spontaneous parametric down-conversion. Specifically, by attempting down-conversion several times, we can pseudodeterministically add photons to a mode, producing various several-photon states, e.g., Fock states and N00N states (number-path entangled states of the form |N(A), 0(B)>+|0(A), N(B)>). This scheme is exponentially more efficient than previous proposals; we discuss expected performance and experimental limitations.
Efficiently creating optical quantum states, both simple (e.g., pure single-photon states) and complex (e.g., polarization-entangled but spectrally unentangled photon pairs), remains an experimental challenge. We report on a novel method that allows for efficiently preparing certain classes of states: by weakly driving repeated downconversion in a cavity, we can pseudo-deterministically add photons to a state, preparing Fock states of definite photon number. We discuss expected performance and experimental limitations, including the difficulty of creating pure photons at a high rate. Additionally, we report on our progress in engineering high-rate spatio-spectrally unentangled downconversion, a key technology for optical quantum information processing, and propose a novel 4-photon experimental scheme to test the intrinsic indistinguishability of the photons from this source.