Photons ‘Photocopied’ for Quantum Computing
GAITHERSBURG, Md., Nov. 3, 2011 — Photon particles from two disparate sources have been rendered indistinguishable without losing their essential quantum properties, suggesting, in principle, that they can connect different types of hardware devices into a single quantum information network and communicate effectively.
 A single photon is produced by a quantum dot (QD). Simultaneously, a pair of photons is produced by a parametric down-conversion crystal (PDC).  One of the PDC photons, which has characteristics different from the QD photon, is routed into a cavity and filter,  rendering this PDC photon and the QD photon nearly identical. (Image: Suplee, NIST)
Researchers from the National Institute of Standards and Technology (NIST) connected single photons from a quantum dot — which could be useful in logic circuits — with a second single-photon source that uses parametric down conversion, which might be used to connect different parts of the computer. These two sources typically produce photons that differ so dramatically in spectrum that they would be unusable in a quantum network. However, with a deft choice of filters and other devices that alter the photons’ spectral shapes and other properties, the team made the photons virtually identical.
“We manipulate the photons to be as indistinguishable as possible in terms of spectra, location and polarization — the details you need to describe a photon. We attribute the remaining distinguishability to properties of the quantum dot,” said Glenn Solomon of NIST’s Quantum Measurement Div. “No conceivable measurement can tell indistinguishable photons apart. The results prove in principle that a hybrid quantum network is possible and can be scaled up for use in a quantum network.”
For more information, visit: www.nist.gov
- logic circuit
- A computer circuit that supplies the action of problem-solving functions or operations.
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