Sacha Schwarz, Jean-Philippe MacLean and Kevin Resch The generation of ultrafast laser pulses and their reconstruction is essential for many applications in modern optics. Quantum optical fields can also be generated on ultrafast time scales, however, the methods available for strong laser pulses are not appropriate for measuring the properties of weak, possibly entangled pulses. Here, we demonstrate a method to reconstruct the joint-spectral amplitude and phase of a two-photon energy-time entangled state from joint measurements in frequency and time. Our reconstruction method is based on a modified Gerchberg-Saxton algorithm. Such techniques are essential to measure and control the shape of ultrafast entangled photon pulses.
