Phys.org April 6, 2021 Researchers at the Fermi National Accelerator Laboratory have developed two new algorithms that build upon existing work to in the field to further diversify the types of problems quantum computers can solve. To get around the probabilistic nature of superpositions the researchers developed the non-Boolean quantum amplitude amplification algorithm which is open to more tasks. A second algorithm they introduced dubbed the quantum mean estimation algorithm allows scientists to estimate the average. Both algorithms do away with having to reduce scenarios into computations with only two types of output, and instead allow for a range of […]
Tag Archives: Quantum technology
Researchers report breakthrough that enables practical semiconductor spintronics
Phys.org April 8, 2021 By remote spin filtering of InAs quantum-dot electrons via an adjacent tunnelling-coupled GaNAs spin filter an international team of researchers (Sweden, Finland, Japan) demonstrated successful generation of conduction electron spin polarization exceeding 90% at room temperature without a magnetic field in a non-magnetic all-semiconductor nanostructure, which remains high even up to 110 °C. They also showed that the quantum-dot electron spin can be remotely manipulated by spin control in the adjacent spin filter, paving the way for remote spin encoding and writing of quantum memory as well as for remote spin control of spin–photon interfaces. This work […]
Spin-to-charge conversion achieves 95% overall qubit readout fidelity
EurekAlert April 1, 2021 The current single-shot readout of the nitrogen-vacancy electron spin relies on resonance fluorescence method at cryogenic temperature. However, the spin-flip process interrupts the optical cycling transition, therefore, limits the readout fidelity. Researchers in China have introduced a spin-to-charge conversion method assisted by near-infrared light to suppress the spin-flip error which leverages high spin-selectivity of cryogenic resonance excitation and flexibility of photoionization. They achieved an overall fidelity > 95% for the single-shot readout of an NV center electron spin in the presence of high strain and fast spin-flip process. With further improvements, this technique has the potential to achieve […]
Study shows promise of quantum computing using factory-made silicon chips
Phys.org March 31, 2021 An international team of researchers (UK, France) measured an electron spin in a singly occupied gate-defined quantum dot, fabricated using CMOS-compatible processes at the 300-mm wafer scale. For readout, they used spin-dependent tunneling combined with a low-footprint single-lead quantum-dot charge sensor, measured using rf gate reflectometry. They demonstrated spin readout in two devices using this technique, obtaining valley splittings in the range 0.5–0.7 meV using excited-state spectroscopy, and measured a maximum electron-spin relaxation time. These long lifetimes indicate the silicon-nanowire geometry and fabrication processes employed here show a great deal of promise for qubit devices, while […]
Detecting photons transporting qubits without destroying quantum information
Phys.org March 25, 2021 Photons that carry qubits over long distances are easily deflected from their path in the air or absorbed in glass fibers—and suddenly, the quantum information is lost. An international team of researchers (Germany, Spain) has developed a physical protocol that can indicate whether the qubit is lost at intermediate stations of the quantum transmission. If this is the case, the transmitter can send the qubit again with significantly less delay than if the loss is noticed only at the receiving end. The protocol only detects the qubit photon and not measure it. They achieved a nondestructive […]
Optical fiber could boost power of superconducting quantum computers
Science Daily March 24, 2021 In superconducting quantum processors, each qubit is individually addressed with microwave signal lines that connect room-temperature electronics to the cryogenic environment of the quantum circuit. The complexity and heat load associated with the multiple coaxial lines per qubit limits the maximum possible size of a processor to a few thousand qubits. A team of researchers in the US (NIST, Boulder CO, University of Colorado) has introduced a photonic link using an optical fibre to guide modulated laser light from room temperature to a cryogenic photodetector, capable of delivering shot-noise-limited microwave signals directly at millikelvin temperatures. […]
Colloidal quantum dot lasers poised to come of age
Nanowerk February 18, 2021 A team of researchers in the US (Los Alamos National Laboratory, Argonne National Laboratory) sums up the recent progress in colloidal-quantum-dot research and highlights the remaining challenges and opportunities in the rapidly developing field, which is poised to enable a wide array of new laser-based and LED-based technology applications. According to the researchers these tiny specs of semiconductor matter can generate spectrally tunable lasing light, opening tremendous opportunities in areas of photonic circuits, optical communications, lab-on-a-chip sensing, and medical diagnostics. They conclude that the accumulated knowledge, along with the approaches developed for manipulating the optical-gain properties […]
Nanofibers for quantum technologies at room temperature
Nanowerk February 18, 2021 The faithful mapping of information between matter and light can facilitate communication between distant quantum processing nodes. Strong interaction benefits from tightly confined light fields, as well as from many atoms interacting simultaneously with such fields. An international team of researchers (Austria, Germany Israel) realized efficient light-matter interface by gradually thinning an optical fiber down to a diameter of 200 nm, about 600 times narrower than its original width, and about a quarter of the optical wavelength guided by the fiber. Reaching these dimensions resulted in a unique optical field with more than 99% of the […]
Scientists create armor for fragile quantum technology
Phys.org February 8, 2021 Integration of TMDCs into practical all‐dielectric heterostructures hinges on the ability to passivate and protect them against necessary fabrication steps on large scales. An international team of researchers (Australia, Germany) has created the protective layer by exposing a droplet of liquid gallium to air, which immediately formed a perfectly even three nanometers thick layer of gallium oxide on its surface. By squashing the droplet on top of the 2D material with a glass slide, the gallium oxide layer can be transferred from the liquid gallium onto the material’s entire surface, up to centimetres in scale. Because […]
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 […]