“This is a very important fundamental achievement as no one has ever seen a photon a second time,”

says Ferdinand Schmidt-Kaler at the University of Ulm in Germany.

This is pretty impressive. Think about that. No one has ever "seen" a photon a second time.

Photon's life cycle 'watched' in full

• 18:00 14 March 2007
• NewScientist.com news service
• Amarendra Swarup

Enlarge image

Superconducting mirrors made of copper covered by a thin layer of niobium. These mirrors are able to store microwave photons up to one-tenth of a second (Image: Michel Brune)

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.

Trapped and annihilated

To observe the photon, the researchers passed rubidium atoms across the cavity one at a time. A single rubidium atom is unable to absorb a single photon, because the photon is not the correct package of energy to boost the rubidium atom to a different energy state.

However, the photon's electric field slightly shifts the atom’s energy levels by a measurable amount (once the atom has emerged), which the team used to determine whether there were any trapped photons.

“This is not performed at the expense of the photon energy, so if one is detected, it is still there afterwards for successive rubidium atoms, allowing us to track it,” says Haroche. “A typical signal has a sequence of atoms at one energy level, meaning an empty cavity, suddenly interrupted by atoms at another energy level, signalling the photon birth. Later, a jump in the opposite direction signals the photon annihilation.”

Truly, we are living in the future.

Just coincidentally, another current article (about D-mesons spontaneously changing into anti-D-mesons) describes more interactions between "virtual" particles and regular ones:

By observing the rare process of D-meson mixing, BaBar collaborators can test the intricacies of the Standard Model. To switch from matter to antimatter, the D-meson must interact with "virtual particles," which through quantum fluctuations pop into existence for a brief moment before disappearing again. Their momentary existence is enough to spark the D-meson's transformation into an anti-D-meson.

What's mind-blowing to me is that these "virtual" particles were theoretical originally. Someone (Feinman?) figured they must exist. There's an experiment that shows their existence (by measuring the force between two very close plates) but I've never heard of any other effects caused by them.

Harnessing the energy of "virtual particles" is one of the Holy Grails of "free energy" research, which on it's face sounds as wacky as these "virtual particles."

Reminds me of something the Firesign Theater used to say:

"Living in the Future is like having Bees in your head. But there they are!"