  Quantum states of light having a Wigner function with negative values
represent a key resource in quantum communication and quantum information
processing. Here, we present the generation of such a state at the
telecommunication wavelength of 1550nm. The state is generated by means of
photon subtraction from a weakly squeezed vacuum state and is heralded by the
`click' of a single photon counter. Balanced homodyne detection is applied to
reconstruct the Wigner function, also yielding the state's photon number
distribution. The heralding photons are frequency up-converted to 532nm to
allow for the use of a room-temperature (silicon) avalanche photo diode. The
Wigner function reads W(0,0)=-0.063 +/- 0.004 at the origin of phase space,
which certifies negativity with more than 15 standard deviations.
