Subtraction and Addition of Propagating Photons by Two-Level Emitters.

Coherent manipulation of quantum states of light is key to photonic quantum information processing. In this Letter, we show that a passive two-level nonlinearity suffices to implement non-Gaussian quantum operations on propagating field modes. In particular, the collective light-matter interaction can efficiently extract a single photon from a multiphoton input wave packet to an orthogonal temporal mode.

Precision Measurement of Trident Production in Strong Electromagnetic Fields.

We demonstrate experimentally that the trident process e^{-}→e^{-}e^{+}e^{-} in a strong external field, with a spatial extension comparable to the effective radiation length, is well understood theoretically. The experiment, conducted at CERN, probes values for the strong field parameter χ up to 2.4.

Deterministic Photon Sorting in Waveguide QED Systems.

Sorting quantum fields into different modes according to their Fock-space quantum numbers is a highly desirable quantum operation. In this Letter, we show that a pair of two-level emitters, chirally coupled to a waveguide, may scatter single- and two-photon components of an input pulse into orthogonal temporal modes with a fidelity ≳0.9997.