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 […]
Category Archives: Quantum computing
Graphene-hBN breakthrough to spur new LEDs, quantum computing
Science Daily April 14, 2022 Graphene-hBN structures can power LEDs that generate deep-UV light, which is impossible in today’s LEDs. Previous efforts to get ordered rows of hBN atoms that align with the graphene underneath were not successful. A team of researchers in the US (University of Michigan, Ohio State University, Yale University) discovered that neat rows of hBN atoms are more stable at high temperature than the undesirable jagged formations. They used a terraced graphene substrate and heated it to around 1600 degrees Celsius before spraying on individual boron and active nitrogen atoms resulting in neatly ordered seams of […]
In race to build quantum computing hardware, silicon begins to shine
Phys.org April 6, 2022 A team of researchers in the US (Princeton University, Sandia National Laboratory) used a two qubits silicon device and forced them to interact. The spin state of each electron can be used as a qubit and the interaction between the electrons can entangle these qubits. To do this they constructed a cage in the form of a wafer-thin semiconductor made primarily out of silicon. At the top of the cage they patterned little electrodes, which create the electrostatic potential used to corral the electron. Two of these cages put together, separated by a barrier, or gate, […]
Tiny materials lead to a big advance in quantum computing
MIT News January 27, 2022 An international team of researchers (USA – MIT, MIT Lincoln Laboratory, Japan) used hexagonal boron nitride to build a parallel-plate capacitor for a qubit. To fabricate the capacitor, they sandwiched hexagonal boron nitride between very thin layers of another van der Waals material, niobium diselenide and connected the capacitor to the existing structure and cooled the qubit to 20 millikelvins (-273.13 C). The resulting qubit was about 100 times smaller than what they made with traditional techniques on the same chip. The coherence time, or lifetime, of the qubit was only a few microseconds shorter […]
A-list candidate for fault-free quantum computing delivers surprise
Science Daily December 22, 2021 Spin-triplet pairing is important because it can host topological states and majorana fermions relevant for quantum computation. Because spin-triplet pairing is usually mediated by ferromagnetic (FM) spin fluctuations, uranium-based materials near an FM instability are ideal candidates for realizing spin-triplet superconductivity. UTe2 has been identified as a candidate for a chiral spin-triplet topological superconductor near an FM instability, although it also has antiferromagnetic (AF) spin fluctuations. A team of researchers in the US (Rice University, Florida State University, Oak Ridge National Laboratory, UC San Diego, Arizona State University) used inelastic neutron scattering (INS) to show […]
Crucial leap in error mitigation for quantum computers
Phys.org December 9, 2021 Coherent errors severely limit the performance of quantum algorithms in an unpredictable manner, and mitigating their impact is necessary for realizing reliable quantum computations. The average error rates measured by randomized benchmarking and related protocols are not sensitive to the full impact of coherent errors and therefore do not reliably predict the global performance of quantum algorithms. Randomized compiling is designed to overcome these performance limitations by converting coherent errors into stochastic noise, dramatically reducing unpredictable errors in quantum algorithms, and enabling accurate predictions of algorithmic performance from error rates measured via cycle benchmarking. An international […]
A new way to control qubits
Phys.org September 22, 2021 A team of researchers in the US (NIST, University of Colorado, Lawrence Livermore National Laboratory, University of Oregon, UT Austin) demonstrated high-fidelity laser-free universal control of two trapped-ion qubits by creating both symmetric and antisymmetric maximally entangled states with fidelities of 1+0−0.0017 and 0.9977+0.0010−0.0013, respectively (68 per cent confidence level), corrected for initialization error. They used a scheme based on radiofrequency magnetic field gradients combined with microwave magnetic fields that is robust against multiple sources of decoherence and usable with essentially any trapped ion species. The scheme has the potential to perform simultaneous entangling operations on […]
Magnetic field turns handed superconductor into liquid crystal-like nematic state
Nanowerk September 15, 2021 Recent measurements of the resistivity in magic-angle twisted bilayer graphene near the superconducting transition temperature show twofold anisotropy, or nematicity, when changing the direction of an in-plane magnetic field. This was interpreted as strong evidence for exotic nematic superconductivity instead of the widely proposed chiral superconductivity. An international team of researchers (Germany, USA – the Flatiron Institute, Spain) has suggested a surprising connection between the nematic behavior of a superconductor in a magnetic field and its spiral-like ground state in the absence of the field. Their theory could not only explain recent experiments on twisted bilayer […]
New approach to information transfer reaches quantum speed limit
Phys.org August 5, 2021 A team of researchers in the US (University of Maryland, University of Colorado) designed a quantum protocol that reaches the theoretical speed limits for certain quantum tasks. In the new protocol, data stored on one qubit is shared with its neighbors using entanglement. The qubits work together to spread it to other sets of qubits. Because more qubits are involved, they transfer the information even more quickly. This process can be repeated to generate larger blocks of qubits that pass the information faster and faster. They found that the snowballing qubits speed along the information at […]
Combining two approaches to advance quantum computing
Phys.org July 26, 2021 An international team of researchers (USA – Yale University, the Netherland, Spain, Denmark, Sweden) experimentally demonstrated a new qubit that fuses the electromagnetic modes of superconducting circuits and the spins of small numbers of electrons trapped in semiconductor quantum dots. They were able to show how to harness this spin-dependent supercurrent to achieve both spin detection and coherent spin manipulation. The work represents a significant advancement to our understanding and control of Andreev levels which are microscopic, electronic states that exist in all Josephson junctions. In superconductor-semiconductor heterostructures such as the nanowire junctions investigated in this […]