Figure 1 - A Picasso drawing reproduced on the nanoscale with SNOL [1].

Exposing optically active surfaces to patterns of light (photolithography) is the primary method used for fabricating microelectronic (and mechanical) circuits. Requirements for smaller and faster circuits are resulting in several novel means for using light to fabricate nanoscale features. Due to the far-field diffraction limit, light can only be focused to half of its wavelength by traditional means. However, researchers are finding new ways to surpass this barrier in order to allow the fabrication of the next generation of computer chips.

Several methods are now available to the chip designer who wishes to use optical means for fabricating circuits (or other devices) with features smaller than half of the wavelength of light used. Stimulated emission depletion is one technique that has effectively broken the diffraction barrier by exciting localized fluorescence. Another promising method is quantum interferometry. This method takes advantage of the quantum mechanical principle known as entanglement
. When two photons are entangled, they behave as though they have half the wavelength, and can thus be focused twice as efficiently. Entangling more photons results in an even smaller effective wavelength.

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