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| Source: Photonics.com |
Quantum physicist Stephan Ritter and his colleagues at the Max Planck Institute of Quantum Optics in Garching, Germany, wanted to follow up on a 2004 proposal of a nondestructive method for detecting photons. Instead of capturing photons, this instrument would sense their presence, taking advantage of the eccentric realm of quantum mechanics in which particles can exist in multiple states and roam in multiple places simultaneously.
The trick was manipulating the rubidium so that it was in a so-called quantum superposition of these two states, allowing one atom to be an overachiever and a slacker at the same time. Consequently, each incoming photon took multiple paths simultaneously, both slipping into the cavity undetected and being stopped at the door and reflected away. Each time the attentive state of the rubidium turned away a photon, a measurable property of the atom called its phase changed. If the phases of the two states of the rubidium atom differed, the researchers knew that the atom had encountered a photon.
Science News: Single photon detected but not destroyed
Quantum Dynamics Homepage: Dr. Stephan Ritter
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