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Primeur weekly 2019-08-26

Quantum computing

Atos and C-DAC sign Cooperation Agreement for global advancement in Quantum Computing, Artificial Intelligence and Exascale Computing in India ...

Quantum computers to become portable ...

Detraction-free light-matter interaction ...

A University of Massachusetts researcher is shaping the future of technology ...

Schrödinger's cat with 20 qubits ...

Focus on Europe

Registration opens for HPC User Forums at CSCS and EPCC ...

EXDCI to issue Call for Proposals for project spin-off ...

PRACE Autumn School 2019 to address Big Data and HPC ...

Hardware

IBM demonstrates commitment to open hardware movement ...

HPE builds NASA new supercomputer to support future human mission to moon ...

Xilinx announces the world's largest FPGA featuring 9 million system logic cells ...

NetApp provides faster, more efficient solution for analytics and HPC applications ...

Applications

Katharine Cahill named mentor for NSF XSEDE Campus Champion Fellow ...

First Monterey Data Conference does deep dive into Deep Learning for Science ...

Researchers get first microscopic look at a tiny phenomenon with big potential implications ...

Computer model could help test new sickle cell drugs ...

NJIT's Bipin Rajendran is named a Senior Member of the National Academy of Inventors ...

Sofja Kovalevskaja Award brings superconducting spintronics expertise to Konstanz ...

eScience Center and SURF to organize workshop on Machine Learning ...

XSEDE supercomputers aid in novel simulations of X-ray laser research laser pulse visualizations powered by SDSC and TACC supercomputers ...

The Cloud

NVIDIA and VMware to accelerate machine learning, data science and AI workloads on VMware Cloud on AWS accelerated by NVIDIA GPUs ...

VMware announces VMware Tanzu portfolio to transform the way enterprises build, run and manage software on Kubernetes ...

IBM developing new Cloud services and technology to help keep data secured from future fault-tolerant quantum computers ...

Detraction-free light-matter interaction


Sven Scholz (left) and Arne Ludwig are experts for generating quantum dots in semiconductors. Credit: RUB, Kramer.
23 Aug 2019 Bochum - Certain semiconductor structures, so-called quantum dots, might constitute the foundation of quantum communication. They are an efficient interface between matter and light, with photons - light particles - emitted by the quantum dots transporting information across large distances. However, structures form by default during the manufacture of quantum dots that interfere with communication.

Researchers at the University of Basel, Ruhr-Universität Bochum, and Forschungszentrum Jülich have now successfully eliminated these interferences. They've published their report in the journal Communications Physics from 9 August 2019.

Quantum dots can be realised in semiconductors if researchers lock an electron and an electron hole - i.e. a positive charge at a position where an electron should exist - in a constricted space. Together, electron and electron hole form an excited state. When they recombine, the excited state disappears and a photon is generated. "That photon might be usable as information carrier in quantum communication across large distances", stated Dr. Arne Ludwig from the Chair for Applied Solid State Physics in Bochum.

The quantum dots manufactured in Bochum are generated in the semiconductor material indium arsenide. The researchers grow the material on a gallium arsenide substrate. In the process, a smooth indium arsenide layer forms at a thickness of a mere one and a half atomic layers - the so-called wetting layer. Subsequently, the researchers generate small islands with a diameter of 30 nanometres and a height of a few nanometres. These are the quantum dots.

The wetting layer that has to be deposited in the first step causes problems, because it, too, contains excited electron hole states that decay and may release photons. In the wetting layer, these states decay even more easily than in the quantum dots. The photons emitted in the process can't be used in quantum communication, however; rather, they generate a static noise in the system.

"The wetting layer covers the entire surface while the quantum dots only cover a thousandth of the semiconductor chip, which is why the interfering light is approximately a thousand times stronger than the light emitted by the quantum dots", explained Andreas Wieck, Head of the Chair for Applied Solid State Physics in Bochum. "The wetting layer radiates photons at a slightly higher frequency and at a much higher intensity than the quantum dots. It's as if the quantum dots emitted the chamber pitch A, whereas the wetting layer emitted an B that was a thousand times louder."

"We have been able to ignore those interferences by exciting only the required energy states", stated Matthias Löbl from the University of Basel. "However, if quantum dots are to be used as information units for quantum applications, it might be ideal to charge them with more electrons. But in that case, the energy levels in the wetting layer would be likewise excited", added Arne Ludwig.

The research team has now eliminated this interference by adding an aluminium arsenide layer grown above the quantum dots in the wetting layer. The energy states in the wetting layer are thus removed, which, in turn, makes it less likely for electrons and electron holes to recombine and emit photons.

The samples for the current project were generated by Dr. Sven Scholz at the RUB Chair of Applied Solid State Physics, whose work was awarded with the dissertation prize by the Wilhelm and Else Heraeus Foundation in June 2019. The measurements of the size of interferences with and without the aluminium arsenide layer were conducted by the team at the University of Basel, under the auspices of Matthias Löbl, Dr. Immo Söllner and Professor Richard Warburton. The group at Forschungszentrum Jülich captured high-resolution microscope images of the samples.

Source: Ruhr-University Bochum

Back to Table of contents

Primeur weekly 2019-08-26

Quantum computing

Atos and C-DAC sign Cooperation Agreement for global advancement in Quantum Computing, Artificial Intelligence and Exascale Computing in India ...

Quantum computers to become portable ...

Detraction-free light-matter interaction ...

A University of Massachusetts researcher is shaping the future of technology ...

Schrödinger's cat with 20 qubits ...

Focus on Europe

Registration opens for HPC User Forums at CSCS and EPCC ...

EXDCI to issue Call for Proposals for project spin-off ...

PRACE Autumn School 2019 to address Big Data and HPC ...

Hardware

IBM demonstrates commitment to open hardware movement ...

HPE builds NASA new supercomputer to support future human mission to moon ...

Xilinx announces the world's largest FPGA featuring 9 million system logic cells ...

NetApp provides faster, more efficient solution for analytics and HPC applications ...

Applications

Katharine Cahill named mentor for NSF XSEDE Campus Champion Fellow ...

First Monterey Data Conference does deep dive into Deep Learning for Science ...

Researchers get first microscopic look at a tiny phenomenon with big potential implications ...

Computer model could help test new sickle cell drugs ...

NJIT's Bipin Rajendran is named a Senior Member of the National Academy of Inventors ...

Sofja Kovalevskaja Award brings superconducting spintronics expertise to Konstanz ...

eScience Center and SURF to organize workshop on Machine Learning ...

XSEDE supercomputers aid in novel simulations of X-ray laser research laser pulse visualizations powered by SDSC and TACC supercomputers ...

The Cloud

NVIDIA and VMware to accelerate machine learning, data science and AI workloads on VMware Cloud on AWS accelerated by NVIDIA GPUs ...

VMware announces VMware Tanzu portfolio to transform the way enterprises build, run and manage software on Kubernetes ...

IBM developing new Cloud services and technology to help keep data secured from future fault-tolerant quantum computers ...