Physicists from the Universities of Sydney and Basel have demonstrated for the first time the ability to manipulate
Stimulated emission - generation of a new photonduring the transition of a quantum system from one state to another - was described by Albert Einstein and is used to operate lasers. Traditionally, it is observed for many photons. In a new study, physicists have observed stimulated emission of single photons. They measured the direct time delay between a single photon and a pair of bound photons scattered by a single quantum dot.
The device we built induced such strong interactions between photons that we were able to observe the difference between one photon interacting with it versus two.
We noticed that one photon is delayed bylonger time compared to two photons. In this really strong photon-photon interaction, two photons become entangled in the form of what is called a two-photon bound state.
Natasha Tomm, co-author of the study from the University of Basel
Experimental (left) and theoretical (right) observation of one-photon and two-photon dispersion of the bound state delay. Image: Natasha Tomm et al., Nature Physics
The "quantum light" that scientists have observedallows for more accurate measurements with better resolution using fewer photons, the scientists say. This may be important for applications in biological microscopy, where high light intensity can damage specimens and when observed objects and phenomena are especially small.
Light is often used to measure smalldistances using instruments called interferometers. The laws of quantum mechanics set limits on the sensitivity of such devices. This limit is related to how sensitive the measurement can be and the average number of photons in the measurement device. "Quantum light" in these aspects is superior to the laser beam.
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