Spectrally multimode squeezed states generation at telecom wavelengths

We report on the experimental demonstration of a source that generates spectrally multimode squeezed states of light over the infrared C-Band. This is achieved using a single-pass Spontaneous Parametric Down Conversion (SPDC) process in a periodically-poled KTP waveguide that is pumped with the second harmonic of a femtosecond laser. Our measurements show significant squeezing in more than 21 frequency modes, with a maximum squeezing value over 2.5 dB. Moreover, we demonstrate multiparty entanglement across 8 individual frequency bands by measuring the covariance matrix of their quadratures. Finally, we use reconfigurable mode-selective homodyne detection to mold the output into cluster states of various shapes. This result paves the way for the implementation of continuous variable quantum information protocols at telecommunication wavelengths, with applications in multiparty, entanglement-based quantum communication and computation.