Three components for quantum computers integrated on one chip

February 27, 2019 //By Christoph Hammerschmidt
Three components for quantum computers integrated on one chip
Quantum computers are expected to to solve certain computing problems much faster than classical computers. A quantum approach uses single photons for the transmission and processing of information, which is however complex in the technical realization. Researchers at the Karlsruhe Institute of Technology and the University of Stuttgart have for the first time integrated three essential technical components - single photon sources, beam splitters and single photon detectors - on a single compact chip.

"One of the challenges in such an experiment, which was carried out entirely on one chip, was the proximity of the excitation laser to the detectors on the chip," explain Ekkehart Schmidt from KIT and Mario Schwartz from the University of Stuttgart. "The detectors cannot distinguish which photons come from the laser and which from the quantum dot. This leads to unwanted detections." Schmidt and Schwartz have significantly reduced the influence of the laser photons by placing reflective metal layers on the chip.

Nanometer-sized structures - so-called quantum dots - on a platform made of gallium arsenide serve as efficient sources of single photons. Optical logic circuits and special detectors made of superconducting nanowires can also be placed on the same chip. In the experiment carried out by the Knowledgexhaftists, single photons emitted by an optically pumped quantum dot were guided in a photonic waveguide and divided by a beam splitter into two waveguide arms, each equipped with a detector.

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