Versatile engineering of multimode squeezed states by optimizing the pump spectral profile in spontaneous parametric down-conversion

We study the quantum correlations induced by spontaneous parametric down-conversion (SPDC) of a frequency comb. We derive a theoretical method to find the output state corresponding to a pump with an arbitrary spectral profile. After applying it to the relevant example of a spectrally chirped pump, we run an optimization algorithm to numerically find the pump profiles maximizing some target functions. These include the number of independently squeezed modes and the variances of nullifiers defining cluster states used in many continuous-variable quantum information protocols. To assess the advantages of pump-shaping in real experiments we take into account the physical limitations of the pulse shaper.Comment: Updated title, improved presentation and figures, added references, corrected typos. Closer to the version accepted for publicatio

A time/frequency quantum analysis of the light generated by synchronously pumped optical parametric oscillators

We present in this paper a general model for determining the quantum properties of the light generated by a synchronously pumped optical parametric oscillator (SPOPO) operating below threshold. This model considers time and frequency on an equal footing, which allows us to find new quantum properties, related for example to the carrier envelope offset (CEO) phase, and to consider situations that are close to real experiments. We show that, in addition to multimode squeezing in the so-called 'supermodes', the system exhibits quadrature entanglement between frequency combs of opposite CEO phases. We have also determined the quantum properties of the individual pulses and their quantum correlations with the neighboring pulses. Finally, we determine the quantum Cramer-Rao limit for an ultra-short time delay measurement using a given number of pulses generated by the SPOPO.Comment: This is an author-created, un-copyedited version of an article accepted for publication in New Journal of Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher-authenticated version is available online at http://stacks.iop.org/1367-2630/14/04300