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(萌妹社区Org.com) -- "One of the most exciting things about this is that it gives us nice, clean control over the interaction between light and matter," William Kelly tells 萌妹社区Org.com. "Our technique has the potential to give delicate and precise control over how artificial atoms interact with photons."

Kelly is with Raytheon BBN Technologies in Cambridge, Massachusetts. Along with a group of others in BBN鈥檚 Disruptive Information Processing Technologies division, and with scientists from the National Institute of Standards and Technology in Boulder, Colorado, Kelly took part in an experiment designed to observe superposition of states in a superconducting artificial atom. The group鈥檚 results are described in 萌妹社区ical Review Letters: 鈥淒irect Observation of Coherent Population Trapping in a Superconducting Artificial Atom.鈥�

鈥淚n a classical physics, an atom is in only one energy level at a time, referred to as 0, 1, or 2. In quantum mechanics, though, you get superposition states, in which the exact energy of the atom is not well defined,鈥� Kelly explains. 鈥淚n similar experiments, you see a lot of two-state interference. Our experiment, though, showed three-state interference. This is a new effect in these kinds of systems.鈥�

To get this effect, Kelly and his colleagues worked with microwaves. 鈥淚n atomic experiments, this type of thing is done with optical frequencies,鈥� he says. 鈥淎t room temperature it wouldn鈥檛 be feasible to use microwaves because of thermal noise, however at the temperatures we work at thermal noise is not a problem.鈥�

The experiment involved super-cooling a tiny superconducting device, which acts as an artificial atom, to less than one tenth of a degree above absolute zero. 鈥淵ou apply microwaves to this system, coupling an electromagnetic field to the device, and use that to control the state the artificial atom is in. By sending in photons with energies that match the energy gap of the artificial atom, it is possible to get the artificial atom to transition states,鈥� Kelly says.

One of the potential applications of this technique is in quantum information processing. 鈥淭here are different possible platforms for realizing quantum information systems. Superconducting artificial atoms and photons are both candidates with their own advantages and disadvantages,鈥� Kelly points out. 鈥淲ith this technique, we could potentially use the best of both worlds for quantum information processing.鈥� He also points out that there has been a great deal of work done with optical switching, and that down the road this technique could lead to similar work with switching done with microwave frequencies. 鈥淲e could use this as a sort of microwave transistor.鈥�

On a fundamental level, this work could lead to increased knowledge of quantum systems, and the use of artificial atoms. 鈥淭his is the first time we鈥檝e seen coherence in three states in a manmade system,鈥� Kelly says. 鈥淎dditionally, there are interesting possibilities for using this to slow microwaves down, or even stop them.鈥�

Further development is some while down the road, Kelly acknowledges, but there are some interesting opportunities available now. 鈥淲e鈥檙e probably close to using this to demonstrate slow light,鈥� he says. 鈥淗owever, there are a bunch of possible applications. With more study of this system, we should be able to figure out some new ways to advance technology.鈥�

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