12 research outputs found
Strong non-linearity-induced correlations for counter-propagating photons scattering on a two-level emitter
We analytically treat the scattering of two counter-propagating photons on a
two-level emitter embedded in an optical waveguide. We find that the
non-linearity of the emitter can give rise to significant pulse-dependent
directional correlations in the scattered photonic state, which could be
quantified via a reduction in coincident clicks in a Hong-Ou-Mandel measurement
setup, analogous to a linear beam splitter. Changes to the spectra and phase of
the scattered photons, however, would lead to reduced interference with other
photons when implemented in a larger optical circuit. We introduce suitable
fidelity measures which account for these changes, and find that high values
can still be achieved even when accounting for all properties of the scattered
photonic state.Comment: 10 pages, 7 figure
Limitations of two-level emitters as nonlinearities in two-photon controlled-phase gates
We investigate the origin of imperfections in the fidelity of a two-photon
controlled-phase gate based on two-level-emitter non-linearities. We focus on a
passive system that operates without external modulations to enhance its
performance. We demonstrate that the fidelity of the gate is limited by
opposing requirements on the input pulse width for one- and two-photon
scattering events. For one-photon scattering, the spectral pulse width must be
narrow compared to the emitter linewidth, while two-photon scattering processes
require the pulse width and emitter linewidth to be comparable. We find that
these opposing requirements limit the maximum fidelity of the two-photon
controlled-phase gate for Gaussian photon pulses to 84%.Comment: 7 pages, 6 figure