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High-flux, low-power diamond nanowire single-photon source arrays: an enabling material for optical and quantum computing and cryptography

The novel approach taken by the Harvard researchers was to apply top-down nanofabrication techniques to define large arrays of vertically oriented nanowire antennas in a single-crystal diamond substrate. Briefly, structures were made from a commercially available Type Ib diamond crystal. Electron-beam lithography and reactive-ion etching were then used to realize 200-nm-diameter, 2-micron-long diamond nanowires with straight, smooth sidewalls. Nitrogen-vacancy (NV) centers are embedded randomly in fabricated devices because the diamond substrate has a background of natural NV centers that are created during the crystal growth process. A major advantage of the nanowire array platform is that the etching process itself results in mechanically isolated individual NV centers and minimized background fluorescence.

The readily fabricated diamond nanowire arrays retain the crucial properties of an NV center, are compatible with the requirements needed for the realization of scalable quantum systems based on diamond, interface the nano-world of a color center with the macro-world of optical fibers and lenses, and provide a foundation for enabling the integration of NV center-embedded diamond nanostructures into more complex photonic quantum information, sensing, and imaging devices with even higher count levels and lower powers.

Intellectual Property Status: Patent(s) Pending

Applications

The development of a robust light source that emits one photon at a time will allow new technologies such as secure communication through quantum cryptography. Devices based on fluorescent dye molecules, quantum dots and carbon nanotubes have been demonstrated, but none has combined a high single-photon flux with stable, room-temperature operation. Luminescent centers in diamond have recently emerged as a stable alternative, and, in the case of nitrogen-vacancy centers, offer spin quantum bits with optical readout. However, these luminescent centers in bulk diamond crystals have the disadvantage of low photon out-coupling.

The laboratory of Marko Loncar has demonstrated a single-photon source composed of a nitrogen vacancy center in a diamond nanowire, which produces ten times greater flux than bulk diamond devices, while using ten times less power. This result enables a new class of devices for photonic and quantum information processing based on nanostructured diamond, and could have a broader impact in nanoelectromechanical systems, sensing and scanning probe microscopy.

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