A photon with no area




The recent results from the Italian-Brazilian collaboration on the generation of zero-area single-photon pulses have just appeared on PRL and have been highlighted in Physics.

The interaction between atoms and single particles of light, the photons, is a quantum mechanics textbook exercise and lies at the core of novel schemes for the manipulation and storage of quantum information.

An efficient coupling is generally thought to require photons with a well-defined color, corresponding to that absorbed by the atoms. While many efforts are currently aimed at producing light quanta with these characteristics, here we go against the common intuition and show that a single photon of extremely short duration, which thus possesses a wide range of different color hues, can still strongly interact with very monochromatic atoms. The interaction provokes a deep modulation of the photon temporal shape, with positive and negative lobes that result in a null area. However, almost no absorption takes place, so that energy is conserved, and a single, heavily deformed, photon is still present at the end.

The ability to reliably produce and detect such zero-area single photon pulses is not only intriguing from a fundamental point of view, but it also offers exciting new opportunities for quantum information technologies.