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Getting Past Point One

chip
Image: Charles O'Rear

When it comes to producing ever-shrinking silicon chips, photolithography presents one very serious limit. Because the wavelength of visible light--the "tool" with which photolithographers etch wires onto silicon wafers--measures between 400 and 700 nanometers, it's impossible to sculpt features smaller than 200 nanometers wide. But even tinier circuitry--with features around 100 nanometers, or 0.1 micrometers--could power mightier, more efficient computers. And so researchers have eagerly sought ways past this so-called Point One barrier.

Writing in this week's issue of Physical Review Letters, Jonathan Dowling of the California Institute of Technology and his colleagues describe a quirk of quantum physics that might clear the way: photons, the constituent particles in light, don't seem as fat when they enter a state known as entanglement. Only in the quantum realm can two particles become entangled such that anything happening to one affects the other regardless of the distance between them. And when two entangled photons bounce back toward each other and recombine, Dowling reports, they act like a single photon with half the normal wavelength.

The paper describes a setup in which mirrors and beamsplitters direct two entangled photons to recombine on a surface. In theory, the light from such reunited entangled photons could shave out chip features four times smaller than normal light. And if three entangled photons passed through the device, the resulting light could produce features nine times smaller--a size at which classical computer designs would fail anyway.

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