Phys.org July 25, 2023 Coherently driven semiconductor quantum dots are one of the most promising platforms for non-classical light sources and quantum logic gate. However, coherent manipulation of single charge carriers in quantum dots is limited mainly to their lowest orbital states. Ultrafast coherent control of high-orbital states is obstructed by the demand for tunable terahertz pulses. An international team of researchers (UK, Germany, China) demonstrated an all-optical method to control high-orbital states of a hole via a stimulated Auger process. The coherent nature of the Auger process was proved by Rabi oscillation and Ramsey interference. Harnessing this coherence further […]
Tag Archives: Quantum devices
New theory of electron spin to aid quantum devices
Phys.org November 10, 2022 Researchers at Caltech have developed a new theory and numerical calculations to predict spin decoherence in materials with high accuracy. They adapted a theory of electrical transport to study spin and discovered that this method can capture two main mechanisms governing spin decoherence in materials—spin scattering off atomic vibrations, and spin precession modified by atomic vibrations. They could predict spin decoherence times with an accuracy of a few percent of the measured values—down to a billionth of a second—and access microscopic details of spin motion beyond the reach of experiments. Their research tools—computers and quantum mechanics—can […]
Faster and more efficient computer chips thanks to germanium
Science Daily November 8, 2022 The compound semiconductor silicon-germanium has decisive advantages over today’s silicon technology in terms of energy efficiency and achievable clock frequencies. But establishing contacts between metal and semiconductor on a nanoscale in a reliable way is the main problem with a high proportion of germanium than with silicon. An international team of researchers (Austria, Switzerland, France) found a method to create perfect interfaces between aluminium contacts and silicon germanium components on an atomic scale. They produced a thin silicon layer and the silicon-germanium. By heating the structure in a controlled manner a contact was created between […]
Unipolar quantum optoelectronic devices: Higher speeds in free-space optical communications in the midinfrared band
Phys.org November 2, 2022 A recently demonstrated proof-of-concept of high-speed transmission taking advantage of intersubband devices was limited by the short-distance optical path (up to 1 m). An international team of researchers (France, USA -University of Central Florida, University of New Mexico) used an uncooled quantum cascade detector and a nitrogen-cooled quantum well-infrared photodetector to study the possibility of building a long-range link using unipolar quantum optoelectronics. They evaluated the maximum data rate of their link in a back-to-back configuration before adding a Herriott cell to increase the length of the light path up to 31m. By using pulse shaping, […]
Discovery of the one-way superconductor, thought to be impossible
Nanowerk April 27, 2022 Showing magnetic-field-free, single-directional superconductivity with Josephson coupling, it would serve as the building block for next-generation superconducting circuit technology. An international team of researchers (Germany, China, the Netherlands, USA – Princeton University, Johns Hopkins University) has fabricated an inversion symmetry breaking van der Waals heterostructure of NbSe2/Nb3Br8/NbSe2. They demonstrated that even without a magnetic field, the junction can be superconducting with a positive current while being resistive with a negative current. The ΔIc behaviour (the difference between positive and negative critical currents) with magnetic field is symmetric and Josephson coupling is proved through the Fraunhofer pattern. […]
Hydrogen-tuned topological insulators may lead to new platforms in sustainable quantum electronics
Phys.org May 4, 2022 An international team of researchers (USA – City College of New York, Virginia Tech, Oak Ridge National Laboratory, City University of New York, Poland) invented a new facile and powerful technique that uses ionic hydrogen to reduce charge carrier density in the bulk of 3D topological insulators and magnets. It made robust non-dissipative surface or edge quantum conduction channels accessible for manipulation and control. Hydrogen-tuning technique of chalcogen-based topological materials and nanostructures uses insertion and extraction of ionic hydrogen from dilute aqueous hydrochloric acid solution, which leaves the layered topological crystal structure as well as electronic […]
A simpler approach for creating quantum materials
Phys.org May 4, 2022 Using twisted bilayer graphene to make devices remains challenging because of the low yield of fabricating twisted bilayer graphene. Researchers at the University of Pennsylvania have shown how patterned, periodic deformations of a single layer of graphene transforms it into a material with electronic properties previously seen in twisted graphene bilayers. To better understand the quantum geometrical properties of this system, they set out to understand the theory underlying how electrons move in this single-layered system. After running computer simulations of single-layered experiments, the researchers were surprised to find new evidence of unexpected phenomena along the […]
New type of magnetism unveiled in an iconic material
Phys.org October 5, 2021 Using low-energy muon spin spectroscopy an international team of researchers (Italy, Germany, UK, Israel, South Korea, Japan) discovered the existence of surface magnetism in Sr2RuO4 in its normal state. They detected static weak dipolar fields yet manifesting at an onset temperature higher than 50 K. They ascribed this unconventional magnetism to orbital loop currents forming at the reconstructed Sr2RuO4 surface. The results confirm that physical properties can be dramatically modified at a complex material surface and at interfaces within thin film heterostructures, and these modifications can be exploited for discovering new science for basic and applied research […]
Inductance based on a quantum effect has the potential to miniaturize inductors
Phys.org February 5, 2021 The magnitude of the conventional inductance is proportional to the volume of the inductor’s coil, which hinders the miniaturization of inductors. Researchers in Japan have demonstrated an inductance of quantum-mechanical origin, generated by the emergent electric field induced by current-driven dynamics of spin helices in a magnet. In microscale rectangular magnetic devices with nanoscale spin helices, they observed a typical inductance as large as −400 nanohenry, comparable in magnitude to that of a commercial inductor, but in volume about a million times smaller. The inductance is enhanced by nonlinearity in current and shows non-monotonous frequency dependence, […]
Quantum algorithm breakthrough
Science Daily November 16, 2020 A team of researchers in the US (Western Washington University, UC Santa Barbara, University of Michigan, NYCity University) has developed a quantum algorithm that uses quantum gates acting on neighboring qubits in a quasi-one-dimensional setting and its circuit depth is linear in the number of qubits. They identified correlation functions that serve as signatures of the Laughlin state and discussed how to obtain them on a quantum computer. Application of the algorithm provides tools to improve quantum computing devices. The algorithm opens a new venue to use the new quantum devices to study problems which […]