Temporal shaping of entangled photons

We experimentally demonstrate shaping of the two-photon wavefunction of entangled photon-pairs, utilizing coherent pulse-shaping techniques. By performing spectral-phase manipulations we tailor the two-photon wavefunction exactly like a coherent ultrashort pulse. To observe the shaping we perform sum-frequency generation (SFG) with an ultrahigh flux of entangled photons. At the appropriate conditions, SFG performs as a coincidence detector with an ultrashort response time (~100 fs), enabling a direct observation of the two-photon wavefunction. This property also enables us to demonstrate background-free, high-visibility two-photon interference oscillations.