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Primeur weekly 2015-12-07

Quantum computing

A quantum spin on molecular computers ...

Researchers confirm 'realistic' answer to quantum network puzzle ...

Focus on Europe

ISC 2016 introduces PhD Forum and extends deadline for research papers ...

Quantum computer made of standard semiconductor materials ...

Future direction of global research and e-infrastructures landscape in e-IRG/ESFRI organized network session at ICT2015 in Lisbon ...

EGI-UberCloud partnership is bridging research and innovation ...

Finnish ministry issues policy on future development of scientific computing ...

HPC Advisory Council and the ISC High Performance Conference announce university teams for HPCAC-ISC 2016 Student Cluster Competition ...

GEANT agrees new Board, community programme and cost sharing model ...

Spanish Council of Ministers supports the acquisition of MareNostrum 4 ...

NEC's SX-ACE vector supercomputer contributes to research at three German institutes - University of Kiel, Alfred Wegener Institute and the High Performance Computing Center Stuttgart ...

Middleware

TACC's HPC team works to increase technical diversity in supercomputing ...

Hardware

Mellanox promotes Freddy Gabbay to Vice President of Software ...

SanDisk and Supermicro form strategic alliance to deliver software defined all-flash storage solutions ...

Seagate and Newisys demonstrate flash storage architecture capable Of 1TB/s ...

Hewlett Packard Enterprise introduces new class of system to power next era in hybrid infrastructure ...

Applications

Sequoia supercomputer enables Gordon Bell Prize-winning simulation on Earth's mantle ...

Unveiling the turbulent times of a dying star ...

Missing link found between turbulence in collapsing star and hypernova, gamma-ray burst ...

New insights into the creation of heavy elements ...

Manipal Hospitals adopts Watson for Oncology to help physicians identify options for individualized, evidence-based cancer care across India ...

TOP500

Liquid immersion cooling from Green Revolution Cooling helps Tokyo Institute of Technology achieve top honours at Green500 three years in a row ...

The Cloud

Univa announces support for Microsoft Azure ...

Hewlett Packard Enterprise and Microsoft announce plans to deliver integrated hybrid IT infrastructure ...

IBM advances hybrid capabilities to China and unveils Bluemix Local ...

Quantum computer made of standard semiconductor materials


By evaporating indium gallium arsenide onto a gallium arsenide substrate TUM physicists created nanometer-scale hills, so-called quantum dots. An electron trapped in one of these quantum dots can be used to store information. Hitherto unknown memory loss mechanisms could be switched off by applying a magnetic field. Credit: Fabian Flassig/TUM
2 Dec 2015 Munich - Physicists at the Technical University of Munich, the Los Alamos National Laboratory and Stanford University, USA have tracked down semiconductor nanostructure mechanisms that can result in the loss of stored information - and halted the amnesia using an external magnetic field. The new nanostructures comprise common semiconductor materials compatible with standard manufacturing processes.

Quantum bits, qubits for short, are the basic logical elements of quantum information processing (QIP) that may represent the future of computer technology. Since they process problems in a quantum-mechanical manner, such quantum computers might one day solve complex problems much more quickly than currently possible, so the hope of researchers.

In principle, there are various possibilities of implementing qubits: photons are an option equally as viable as confined ions or atoms whose states can be altered in a targeted manner using lasers. The key questions regarding their potential use as memory units are how long information can be stored in the system and which mechanisms might lead to a loss of information.

A team of physicists headed by Alexander Bechtold and Professor Jonathan Finley at the Walter Schottky Institute of the Technical University of Munich and the Cluster of Excellence Nanosystems Initiative Munich (NIM) have now presented a system comprising a single electron trapped in a semiconductor nanostructure. Here, the electron's spin serves as the information carrier.

The researchers were able to precisely demonstrate the existence of different data loss mechanisms and also showed that stored information can nonetheless be retained using an external magnetic field.

The TUM physicists evaporated indium gallium arsenide onto a gallium arsenide substrate to form their nanostructure. As a result of the different lattice spacing of the two semiconductor materials strain is produced at the interface between the crystal grids. The system thus forms nanometer-scale "hills" - so-called quantum dots.

When the quantum dots are cooled down to liquid helium temperatures and optically excited, a singe electron can be trapped in each of the quantum dots. The spin states of the electrons can then be used as information stores. Laser pulses can read and alter the states optically from outside. This makes the system ideal as a building block for future quantum computers.

Spin up or spin down correspond to the standard logical information units 0 and 1. But, on top of this come additional intermediate states of quantum mechanical up and down superpositions.

However, there is one problem: "We found out that the strain in the semiconductor material leads to a new and until recently unknown mechanism that results in the loss of quantum information", stated Alexander Bechtold. The strain creates tiny electric fields in the semiconductor that influence the nuclear spin orientation of the atomic nuclei.

"It's a kind of piezoelectric effect", stated Alexander Bechthold. "It results in uncontrolled fluctuations in the nuclear spins." These can, in turn, modify the spin of the electrons, i.e. the stored information. The information is lost within a few hundred nanoseconds.

In addition, Alexander Bechthold's team was able to provide concrete evidence for further information loss mechanisms, for example that electron spins are generally influenced by the spins of the surrounding 100,000 atomic nuclei.

"However, both loss channels can be switched off when a magnetic field of around 1.5 tesla is applied", stated Alexander Bechtold. "This corresponds to the magnetic field strength of a strong permanent magnet. It stabilizes the nuclear spins and the encoded information remains intact."

"Overall, the system is extremely promising", according to Jonathan Finley, head of the research group. "The semiconductor quantum dots have the advantage that they harmonize perfectly with existing computer technology since they are made of similar semiconductor material." They could even be equipped with electrical contacts, allowing them to be controlled not only optically using a laser, but also using voltage pulses.

The research was funded by the European Union (S3 Nano and BaCaTeC), the US Department of Energy, the US Army Research Office (ARO), the German Research Foundation DFG - Cluster of Excellence Nanosystems Munich (NIM) and SFB 631, the Alexander von Humboldt Foundation as well as the TUM Institute for Advanced Study (Focus Group Nanophotonics and Quantum Optics).

"Three-stage decoherence dynamics of an electron spin qubit in an optically active quantum dot" is authored by Alexander Bechtold, Dominik Rauch, Fuxiang Li, Tobias Simmet, Per-Lennart Ardelt, Armin Regler, Kai Müller, Nikolai A. Sinitsyn, and Jonathan J. Finley. The paper is published inNature Physics, 11, 1005-1008 (2015) - DOI: 10.1038/nphys3470
Source: Technical University of Munich - TUM

Back to Table of contents

Primeur weekly 2015-12-07

Quantum computing

A quantum spin on molecular computers ...

Researchers confirm 'realistic' answer to quantum network puzzle ...

Focus on Europe

ISC 2016 introduces PhD Forum and extends deadline for research papers ...

Quantum computer made of standard semiconductor materials ...

Future direction of global research and e-infrastructures landscape in e-IRG/ESFRI organized network session at ICT2015 in Lisbon ...

EGI-UberCloud partnership is bridging research and innovation ...

Finnish ministry issues policy on future development of scientific computing ...

HPC Advisory Council and the ISC High Performance Conference announce university teams for HPCAC-ISC 2016 Student Cluster Competition ...

GEANT agrees new Board, community programme and cost sharing model ...

Spanish Council of Ministers supports the acquisition of MareNostrum 4 ...

NEC's SX-ACE vector supercomputer contributes to research at three German institutes - University of Kiel, Alfred Wegener Institute and the High Performance Computing Center Stuttgart ...

Middleware

TACC's HPC team works to increase technical diversity in supercomputing ...

Hardware

Mellanox promotes Freddy Gabbay to Vice President of Software ...

SanDisk and Supermicro form strategic alliance to deliver software defined all-flash storage solutions ...

Seagate and Newisys demonstrate flash storage architecture capable Of 1TB/s ...

Hewlett Packard Enterprise introduces new class of system to power next era in hybrid infrastructure ...

Applications

Sequoia supercomputer enables Gordon Bell Prize-winning simulation on Earth's mantle ...

Unveiling the turbulent times of a dying star ...

Missing link found between turbulence in collapsing star and hypernova, gamma-ray burst ...

New insights into the creation of heavy elements ...

Manipal Hospitals adopts Watson for Oncology to help physicians identify options for individualized, evidence-based cancer care across India ...

TOP500

Liquid immersion cooling from Green Revolution Cooling helps Tokyo Institute of Technology achieve top honours at Green500 three years in a row ...

The Cloud

Univa announces support for Microsoft Azure ...

Hewlett Packard Enterprise and Microsoft announce plans to deliver integrated hybrid IT infrastructure ...

IBM advances hybrid capabilities to China and unveils Bluemix Local ...