IBM Demos Atomic-Scale Circuitry

Christopher Pereda sends us a LA Times story about IBM demonstrating atomic scale circuitry. Or see IBM's press release. Who needs Coppermine?

Comments

Re:How do you read the "mirage"

[irongull]

IANAQP (I am not a quantum physicist) but I do have a Nature online account, and I've read the actual scientific paper, so I'll take a stab at it.

This 'echo' is actually an echo of something called the Kondo effect. Basically, when you have a single magnetic molecule (like cobalt) in a non-magnetic metal (like copper) and you lower the temperature, the electrons on the surface of the copper begin to align their spins to cancel the magnetic moment of the cobalt atom. At sufficiently low temp, these shielding electrons enter a many-particle single-spin quantum state that completely masks the cobalt's magnetic moment. This is the Kondo effect. The ellipse on the Cu surface creates a number of possible waveforms (more properly, eigenstates) that can refocus this resonance to the other focus - creating another Kondo effect where there is no cobalt atom. This effect can be measured with a STM (scanning-tunneling electron microscope). IIRC, STM uses a very, very fine molecular 'tip' that is passed above the sample. As the tip moves over an atomic surface, a tunnelling current is generated that is proportional to the distance between the tip and the sample. This is commonly used to generate topographic maps of electron density around single atoms.

Theoretically, this resonance could be used to sample the orientation of a magnetic molecule at a distance. Of course, measuring this moment would disrupt it as per Heisenberg's Uncertaintly Principle, but in this experiment, they are only measuring the presence of the field, not its orientation. Since the effect disappears when the Co atom is moved off the focus of the ellipse, this could also be used sense small movements of atoms at a distance. And it could be used to link the quantum states of two molecules at a distance on a surface, effectively forming a specific quantum 'wire'. They also speculate that ellipsoids could be used to do this in a 3D solid.

Don't get too excited - the effect only happens at 4K (brrrrr) and an electron microscope is a rather impractical sensor, so don't look for it any time soon. But its still cool.

I may very well have butchered some or all of this explanation. I welcome any corrections or clarifications.

How do you read the "mirage"

[konstant]

For the benefit of those who prefer to think on a more graspable scale, IBM is exploiting an interesting property of closed ellipses. Namely, that a disturbance at once of the focii will create a miraged disturbance at the other focus. If, for example, a swimmer dives into an elliptical pool and strikes a focus, a splash will actually appear at both that focus and the one on the other side of the pool. Similarly, IBM sticks a cobalt atom at one focus of an elliptical ring of cobalt atoms. A miraged cobalt atom appears at the other focus, I'm guessing this is because atoms can be expressed as probability waves - which look a bit like the splash from a diver - and the overlap of all these waves causes an elliptical reflection. If somebody understand particle physics fairly well, I'd appreciate a clarification on that point.

Anyway, what interest me far more is how IBM plans to read the state of this "circuit" without causing a sever disruption, per the Heisenberg uncertainty principle. You can turn the device on or off by pushing the odd cobalt atom around, but surely attempting a read operation on the device would cause its state to alter? Does anyone have ideas as to how they would avoid this?

-konstant
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