Figure 1
(a) Conceptual representation of the experiment. A single photon is injected into the upper (signal) input port, where it is prepared in the state of Eq. (
1) using a polarizing beam splitter (PBS) and half waveplate (
;
). A weak measurement of the polarization is made by interacting the photon with another (meter) photon in a weak measurement device, which operates via measurement-induced nonlinearity [
25]. The interaction of the two photons can be controlled using
. The signal photon is then postselected in the state
using
, a PBS and a photon counter. A coincidence count flags successful postselection of the signal photon, and weak measurement with an outcome corresponding to the final meter waveplate (
) setting. The signal and meter photons are produced in pairs by spontaneous parametric downconversion from a beta-barium borate (BBO) crystal, pumped at 1.2 W at 351.1 nm by an
laser. The mean coincidence rate without postselection on
was
in 0.36 nm bandwidth; the postselection reduced this to
across the measurement outcomes. Photon counting occurred over 100 s when making measurements in the absence of postselection on
. This was increased to 1000 s when postselection on
was included. The coincidence window was 1 ns. We delivered the photons to the experiment through single mode optical fibers to provide Gaussian spatial modes for improved mode matching. (b) Conceptual representation of the weak measurement device [
25,
26]. The entangling operation occurs because of the nonclassical interference at the
beam splitter, and conditional on obtaining one and only one photon at the meter output.
Reuse & Permissions