Nanowerk October 26, 2020 The lack of atomic-scale precision in using current state-of-the-art “top-down” synthetic methods — cutting a graphene sheet into atom-narrow strips – stymie graphene’s practical use. An international team of researchers (USA – Oak Ridge National Laboratory, The University of Tennessee, Poland, Luxembourg) has developed a “bottom-up” approach — building the graphene nanoribbon directly at the atomic level in such a way that it can be used in specific applications. The nanoribbons were synthesized on the surface of rutile titanium dioxide that assisted the cyclode-hydrofluorination of specifically designed precursor molecules through a series of thermally triggered transformations. […]
Tag Archives: Quantum devices
Topological states caught in the act
Nanowerk October 23, 2020 Topological insulators do not conduct electricity in their bulk but channel it along their surface through edge modes. The edge modes can be destroyed only through the use of force. This topological property makes such materials promising candidates in future quantum devices when combined with Floquet engineering. An international team of researchers (USA – SLAC National Accelerator Laboratory, Stanford University, The Flatiron Institute, Spain, Germany, Switzerland) has demonstrated that short corkscrew laser flashes can be used to track these short-lived states. In their earlier work the researchers had demonstrated how to make use of circular dichroism […]
Single photon emission from isolated monolayer islands of InGaN
Phys.org September 23, 2020 An international team of researchers (China, Japan, Germany) developed a novel type of quantum emitter formed from spatially separated monolayer islands of InGaN sandwiched in a GaN matrix. They first grew a planar structure of InGaN monolayer islands using molecular beam epitaxy, and then patterned the sample into pillars using nanoimprint lithography and inductively-coupled plasma reactive-ion etching. Detailed optical analysis of the emission properties of the isolated monolayer islands showed that the main emission line could be spectrally filtered to act as a bright, and fast single photon emitter at a wavelength of ~ 400 nm, […]
A new path for electron optics in solid-state systems
Science Daily July 14, 2020 Electron optics has been demonstrated mainly in one-dimensional devices, for example in nanotubes. Researchers in Switzerland have shown that the band inversion and hybridization present in two coupled semiconductor layers, consisting of InAs and GaSb system provide a novel transport mechanism that guarantees non-vanishing interference even when all angles of incidence occur. Through a combination of transport measurements and theoretical modelling, they found that their devices operate as a Fabry-Pérot interferometer in which electrons and holes form hybrid states. As the mechanism requires only band inversion and hybridization, the research opens engineering electron-optical phenomena in […]
Scientists create new device to light up the way for quantum technologies
Phys.org July 7, 2020 An international team of researchers (Ireland, UK) report theoretical statistics of 1- and 2-qubit (bipartite) systems, namely, photon antibunching and entanglement, of near-field excited quantum emitters. The sub-diffraction focusing of a plasmonic waveguide is shown to generate enough power over a sufficiently small region to strongly drive quantum emitters. This enables ultrafast single-photon emission as well as creates entangled states between two emitters when performing a controlled-NOT operation. The use of a movable plasmonic waveguide, in lieu of stationary nanostructures, allows high-speed rasterization between sets of qubits and enables spatially flexible data storage and quantum information […]
Newly observed phenomenon could lead to new quantum devices
MIT News June 15, 2020 Kohn anomalies reflect a sudden change in the graph describing a change of the capability of electrons for shielding phonons. This can give rise to instabilities in the propagation of electrons through the material and can lead to many new electronic properties. A team of researchers in the US (MIT, Pennsylvania State University, Argonne National Laboratory, Oak Ridge National Laboratory, NIST, University of Maryland) predicted and observed Kohn anomaly in the topological Weyl semimetal (WSM) tantalum phosphide. It exhibits multiple topological singularities of Weyl nodes, leading to a distinct nesting condition with chiral selection, a […]
Controlling photons with a photon
Phys.org June 28, 2018 To realize the strong light-matter interaction that is necessary for all-optical quantum devices, a team of researchers in the US (Harvard University, MIT) used a laser-cooled ensemble of 87Rb atoms (~10 uK) trapped within a high-finesse optical resonator (finesse ~50000) in an ultrahigh-vacuum chamber. To switch a photon with a photon in such a system, they used ‘vacuum-induced transparency’ in which an electromagnetic field as weak as a vacuum field is shown to alter the optical properties of atoms. The research is a step towards deterministic multi-mode entanglement generation as well as high-fidelity photonic quantum gates […]