  In the field of continuous-variable quantum information processing,
non-Gaussian states with negative values of the Wigner function are crucial for
the development of a fault-tolerant universal quantum computer. While several
non-Gaussian states have been generated experimentally, none have been created
using ultrashort optical wave packets, which are necessary for high-speed
quantum computation, in the telecommunication wavelength band where mature
optical communication technology is available. In this paper, we present the
generation of non-Gaussian states on wave packets with a short 8-ps duration in
the 1545.32 nm telecommunication wavelength band using photon subtraction up to
three photons. We used a low-loss, quasi-single spatial mode waveguide optical
parametric amplifier, a superconducting transition edge sensor, and a
phase-locked pulsed homodyne measurement system to observe negative values of
the Wigner function without loss correction up to three-photon subtraction.
These results can be extended to the generation of more complicated
non-Gaussian states and are a key technology in the pursuit of high-speed
optical quantum computation.
