A new strategy to implement a high-fidelity mixed-species entangling gate

Phys.org  September 22, 2020 One of the greatest challenges in the development of trapped ion quantum computers is scalability because adding new qubits to a quantum computing system often results in a rapid decrease in performance, as it introduces new errors and makes it harder to interact with a single qubit without affecting some of the others. Researchers in the UK used modularization and optical networking to have ions in separate ion traps and vacuum systems, which are only connected through optical fibers. This approach limits crosstalk between qubits, retaining only interactions that are desirable and can be controlled by […]

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 […]

New electronic cooling technology to enable miniaturization of quantum computers

Phys.org  April 14, 2020 The optimal operation of electrothermal elements relies on mastering two competing boundary conditions: the maximization of the electrothermal response and the blockade of lattice (phonon) thermal conduction. Researchers in Finland proposed and demonstrated that efficient electrothermal operation and phonon blocking can be achieved in solid-state thermionic junctions, paving the way for new phonon-engineered high-efficiency refrigerators and sensors. For demonstration they used semiconductor-superconductor (Sm-S) junctions where the electrothermal response arises from the superconducting energy gap and the phonon blocking results from the acoustic transmission bottleneck at the junction. They demonstrated a cooling platform where a silicon chip […]

Engineers crack 58-year-old puzzle on way to quantum breakthrough

Phys.org  March 11, 2020 Nuclear spins are featured in early proposals for solid-state quantum computers and demonstrations of quantum search and factoring algorithms. Scaling up such concepts requires controlling individual nuclei which can be detected when coupled to an electron An international team of researchers (Australia, USA – Sandia National Laboratory, Japan) has demonstrated the coherent quantum control of a single 123Sb (spin-7/2) nucleus using localized electric fields produced within a silicon nanoelectronic device. The method exploits an idea proposed in 1961 but not previously realized experimentally with a single nucleus. Their results are quantitatively supported by a microscopic theoretical […]

Blanket of light may give better quantum computers

Phys.org  October 17, 2019 In their efforts to observe quantum phenomena on a macroscopic scale, researchers in Denmark managed to create a network of 30,000 entangled pulses of light arranged in a two-dimensional lattice distributed in space and time. They produced light beams with special quantum mechanical properties (squeezed states) and woven them together using optical fibre components to form a cluster state. An optical quantum computer will therefore not require costly and advanced refrigeration technology, its information-carrying light-based qubits in the laser light will be much more durable and it can be more easily be scaled to contain hundreds […]

A sound idea: a step towards quantum computing

Science Daily  June 19, 2019 An international team of researchers (Japan, USA – University of Pittsburgh) used very short laser pulses to excite electrons inside a silicon crystal creating coherent vibrations of the silicon structure, such that the motions of the electron and the silicon atoms became entangled. The state of the system was then probed after a variable delay time with a second laser pulse. Based on their theoretical model, the scientists were able to explain oscillations observed in the charge generated as a function of delay time. The research may lead to quantum computers based on existing silicon […]

Silicon two-qubit gate achieves 98% fidelity

Physics World  May 13, 2019 Two-qubit gates are essential for creating practical quantum computers. An important parameter is how resistant a qubit is to decoherence which can very quickly destroy quantum information. While the fidelity does not have to be a perfect 100%, anything lower will eventually lead to errors creeping into calculations after multiple operations are performed. An international team of researchers (Australia, UK, Japan) has created a two-qubit gate from two silicon quantum dots and using Clifford-based fidelity benchmarking system they demonstrated that it can achieve a fidelity of 98% when performing the controlled-rotation operation. More than 50 […]