In an important step towards more practical quantum information processing, researchers from the National Institute of Standards and Technology (NIST), the University of California, San Diego; and the Politecnico di Milano in Milan, Italy, have demonstrated the first heralded single photon source made from silicon. This source complements two other recently developed silicon-based technologiesinterferometers for manipulating the entanglement of photons and single photon detectorsneeded to build a quantum optical circuit or a secure quantum communication system.
The line between "interesting" and practical in advanced electronics and optics often comes down to making the new device compatible with existing technology. According to NIST scientist Kartik Srinivasan, the new 0.5 mm x 0.05 mm-sized heralded photon generator meshes with existing technology in three important ways: it operates at room temperature; it produces photons compatible with existing telecommunications systems (wavelengths of about 1550 nanometers); and it's in silicon, and so can be built using standard, scalable fabrication techniques.
A "heralded" photon is one of a pair whose existence is announced by the detection of its partnerthe "herald" photon. To get heralded single photons, the group built upon a technique previously demonstrated in silicon called photon pair generation.
In photon pair generation, a laser pumps photons into a material whose properties cause two incoming pump photons to spontaneously generate a new pair of frequency-shifted photons. However, while these new photons emerge at precisely the same time, it is impossible to know when that will occur.
"Detecting one of these photons, therefore, lets us know to look for its partner," says Srinivasan. "While there are a number of applications for photon pairs, heralded pairs will sometimes be needed, for example, to trigger the storage of information in future quantum-based computer me
|Contact: Mark Esser|
National Institute of Standards and Technology (NIST)