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Oscillating circuits are the workhorses of many electronic devices. In particular, oscillating electrons emit electromagnetic waves, a mechanism that has lead to one or two applications that readers may have come across.

Now Seth Caliga and pals at the University of Colorado and National Institute for Standards and Technology in Boulder have built a version of this kind of circuit that works with atoms rather than electrons. 

Their atomtronic circuit generates an oscillating atom current that emits matter waves in which atoms carry energy through space. 

The heart of their device is an atomtronic transistor–an optomagnetic trap with three compartments that can hold a Bose Einstein Condensate of rubidium atoms cooled almost to absolute zero. 

In an analogy with electronic transistors, Caliga and co call these compartments the source, gate and drain (with the gate sandwiched between the source and drain). The optical barrier between the compartments prevents atoms from moving freely between them.

Caliga and co initiate their atomtronic transistor by filling the source compartment with rubidium atoms. This process is like charging a capacitor: it produces a chemical potential that pushes atoms through the device, just as electric potential drives electrons. 

They then lower the barriers to allow atoms to tunnel into the gate. Of course, the atoms can tunnel back again, which leads to the oscillation.  

The atoms are also able to tunnel from the gate to the drain and out of the device. This is the matter wave emission. 

To prevent the atoms tunnelling back again from the drain, Caliga and co zap this region with a laser beam. This excites the atoms, sending the matter wave out into space. That’s why the device is analogous to an electronic oscillator generating electromagnetic waves in a radio. 

Together, this laser and the input of rubidium atoms to the source are like a battery that powers the device. 

There are one or two limitations, of course. The device stops working when it runs out of atoms, a number that is limited by the number of atoms in a Bose Einstein Condensate, in this case a few tens of thousands. 

The only way to fix this is to generate a continuous source of these atoms, something nobody has yet worked out. But Caliga and co believe it’s a problem that will be cracked in the near future. 

Beyond that, the question is what to do with such a device. Electronic oscillators (and mechanical ones such as grandfather clocks) sit at the heart of some of the greatest revolutions in human history. 

Caliga and co have similarly high hopes for their device: “The matterwave oscillator may likewise have a significant role to play in the development of atom-based sensors, and perhaps in quantum information processing.”

We’ll be waiting to see. In the meantime, suggestions for the way matterwave oscillators might improve our lot in the comments section please.

Ref: http://arxiv.org/abs/1208.3109: A Matterwave Transistor Oscillator

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Tagged: Communications

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