For the first time the birth, life and death of a single photon – a particle of light – has been “watched” in real time.Previously, scientists were restricted to momentary glances because the mere act of measurement absorbed and destroyed the delicate quantum particles.
Now, Serge Haroche and colleagues at the École Normale Supérieure in Paris, France, have succeeded in tracking photons over an average lifetime of 0.13 seconds – long enough for a photon to travel one-tenth of the way to the Moon.
At the heart of their remarkable achievement lies a small box-like cavity, walled with ultra-reflective, superconducting mirrors, which is cooled to just 0.5° above absolute zero (-273.15°C). Photons appear and disappear randomly within the cavity due to tiny energy fluctuations in space that cause quantum particles to blink in and out of existence. However, once there, the photon is trapped, bouncing billions of times between the mirrored walls before it decays.
Posts Tagged ‘photons’
The Birth (and Death) of Light
Friday, March 16th, 2007Single Photon Computing
Monday, March 12th, 2007A team of physicists in the group of Professor Gerhard Rempe at the Max Planck Institute of Quantum Optics in Garching near Munich, Germany, have now built a single-photon server based on a single trapped neutral atom. The high quality of the single photons and their ready availability are important for future quantum information processing experiments with single photons. In the relatively new field of quantum information processing the goal is to make use of quantum mechanics to compute certain tasks much more efficiently than with a classical computer. (Nature Physics online, March 11th, 2007)A single atom, by its nature, can only emit one photon at a time. A single photon can be generated at will by applying a laser pulse to a trapped atom. By putting a single atom between two highly reflective mirrors, a so called cavity, all of these photons are sent in the same direction. Compared with other methods of single-photon generation the photons are of a very high quality, i.e. their energy varies very little, and the properties of the photons can be controlled. They can for instance be made indistinguishable, a property necessary for quantum computation. On the other hand, up to now, it was not possible to trap a neutral atom in a cavity and at the same time generate single photons for a sufficiently long time to make practical usage of the photons.
