Science Daily June 16, 2021 An international team of researchers (USA – University of Minnesota, Pennsylvania State University, Cornell University, National High Magnetic Field Laboratory, China, Switzerland) found that Niobium diselenide (NbSe2) in 2D form is a more resilient superconductor because it has a two-fold symmetry, which is very different from thicker samples of the same material. Despite the six-fold structure, it only showed two-fold behavior in the experiment. They attributed the newly discovered two-fold rotational symmetry of the superconducting state in NbSe2 to the mixing between two closely competing types of superconductivity, namely the conventional s-wave type — typical of […]
Tag Archives: Quantum computing
Light meets superconducting circuits
EurekAlert May 10, 2021 Realizing the full potential of quantum computers requires a significant increase in the number of qubits to store and manipulate quantum information. To prevent contaminating quantum signals by thermal noise, the superconducting quantum systems must operate at ultra-low temperatures. An international team of researchers (Switzerland, India) has developed a novel approach that uses light to read out superconducting circuits. They replaced low-noise high-electron mobility transistors and coaxial cables with a lithium niobate electro-optical phase modulator and optical fibers. Microwave signals from superconducting circuits modulate a laser carrier and encode information on the output light at cryogenic […]
Twistoptics: A new way to control optical nonlinearity
Science Daily March 4, 2021 A hot topic in the field of 2D materials has been exploring how twisting can change the electronic properties of the layered system. van der Waals (vdW) heterostructures feature layers that can be stacked at arbitrary angles, giving complete control over the presence or lack of inversion symmetry at a crystal interface. An international team of researchers (USA – Columbia University, industry, Germany, Japan) demonstrated highly tunable second harmonic generation (SHG) using bulk hexagonal boron nitride crystals and introduced the term twistoptics to describe studies of optical properties in twistable vdW systems. By suppressing residual […]
A speed limit also applies in the quantum world
Science Daily February 19, 2021 In two-level systems, the quantum brachistochrone solutions are long known but they are not applicable to larger systems, especially when the target state cannot be reached through a local transformation. An international team of researchers (Germany, USA – MIT, Italy) has demonstrated fast coherent transport of an atomic wave packet over 15 times its size, a case of quantum processes going beyond the two-level system. The measurements of the transport fidelity revealed the existence of a minimum duration—a quantum speed limit—for the coherent splitting and recombination of matter waves. They obtained physical insight into this […]
UMass Amherst team helps demonstrate spontaneous quantum error correction
EurekAlert February 11, 2021 Existing demonstrations of quantum correction codes (QEC) are hardware intensive and prone to introducing and propagating errors. A team of researchers in the US (UMass Amherst, Northwestern University) encoded a logical qubit in Schrödinger cat-like multiphoton states of a superconducting cavity and demonstrated a corrective dissipation process that stabilizes an error-syndrome operator, the photon number parity. Implemented with continuous-wave control fields only, this passive protocol protects the quantum information by autonomously correcting single-photon-loss errors and boosts the coherence time of the bosonic qubit by over a factor of two. QEC is realized in a modest hardware […]
Tiny bubbles make a quantum leap
EurekAlert July 13, 2020 An international team of researchers (USA – UC Berkeley, Columbia University, industry, Montana State University, Germany, Japan) found that placing sufficient strain in a 2D material–tungsten diselenide creates localized states that can yield single-photon emitters. The team was able to directly image these states for the first time, revealing that even at room temperature they are highly tunable and act as quantum dots, tightly confined pieces of semiconductors that emit light. Fully tunable, room-temperature single-photon emitters are now within our grasp, paving the way for controllable–and practical quantum photonic devices. These devices can be the foundation […]
NIST scientists create new recipe for single-atom transistors
EurekAlert May 11, 2020 Using a room temperature grown locking layer and precise control over the entire fabrication process, a team of researchers in the US (NIST, University of Maryland) reduced unintentional dopant movement while achieving high quality epitaxy in scanning tunneling microscope (STM)-patterned devices. They demonstrated the exponential scaling of the tunneling resistance on the tunnel gap as it is varied from 7 dimer rows to 16 dimer rows, the capability to reproducibly pattern devices with atomic precision and a donor-based fabrication process where atomic scale changes in the patterned tunnel gap result in the expected changes in the […]
The observation of photon-assisted tunneling signatures in Majorana wires
Phys.org May 12, 2020 An International team of researchers (Denmark, USA – UC Santa Barbara, MIT, Caltech, Sweden) has developed a scheme for preparation, manipulation, and read out of Majorana zero modes in semiconducting wires with mesoscopic superconducting islands. They outline a sequence of milestones interpolating between zero-mode detection and quantum computing that includes (1) detection of fusion rules for non-Abelian anyons using either proximal charge sensors or pumped current, (2) validation of a prototype topological qubit, and (3) demonstration of non-Abelian statistics by braiding in a branched geometry. The pre-braiding experiments can be adapted to other manipulation and read […]
New quantum switch turns metals into insulators
EurekAlert February 3, 2020 In a Mott insulator free flow of electrons is facilitated by reducing the strength of the repulsive interaction between electrons, or by changing the number of electrons. An international team of researchers (Canada, Germany, Switzerland, USA – Lawrence Berkeley National Laboratory, Ohio State University, Oak Ridge National Laboratory, South Korea) explored a way to alter the very quantum nature of the material to enable a metal-insulator transition to occur. They found that in Sr2IrO4 coupling the spin to the orbital angular momentum slows the electrons down to such an extent that they become sensitive to one […]
Engineers using soundwaves to search through big data with more stability and ease
Phys.org September 19, 2019 Using three aluminum rods, enough epoxy to connect them and some rubber bands for elasticity researchers at the University of Arizona have demonstrated the possibility for acoustic waves in a classical environment to do the work of quantum information processing without the time limitations and fragility. They sent a wave of sound vibrations down the rods, then monitored two degrees of freedom of the waves: what direction the waves moved down the rods and how the rods moved in relation to one another. To excite the system into a nonseparable state, they identified a frequency at […]