Phys.org June 22, 2021 In a proof of principle experiment researchers at the DOE’s Thomas Jefferson National Accelerator Facility are preparing to trap and levitate particles inside a cavity using an electric field. Intrinsic characteristics of superconducting radiofrequency (SRF) cavities will overcome some limits of laser trapping. If they can levitate a particle, they might be able to impart a quantum state on it by cooling the trapped particle to its lowest possible energy level. A levitated particle in an SRF cavity that is under vacuum and chilled to super cold temperatures will only interact with the cavity’s electric field […]
Category Archives: Quantum computing
A new piece of the quantum computing puzzle
Phys.og June 29, 2021 The challenge in optical quantum information processing has been the realization of two-qubit gates for photonic qubits due to the lack of highly efficient optical Kerr nonlinearities at the single-photon level. A team of researchers in the US (Washington University, University of Michigan) found that a high-fidelity frequency-encoded deterministic two-photon controlled-phase gate can be achieved by exploiting the strong photon-photon correlation enabled by photonic dimers, and the unique nonreciprocal photonic propagation in chiral quantum nanophotonic systems. They are testing the design to show that it can operate under moderate conditions. According to the researchers so far […]
Researchers realize unconventional coherent control of solid-state spin qubits
Phys.org June 9,2021 Optically detected magnetic resonance (ODMR) technology offers a readout approach to detect the spin state. Conventional ODMR detection of solid-state spin states are almost all under Strokes excitation, which requires that the excitation laser has higher energy than emitted photons. An international team of researchers (China, Hungary) investigated the dependence of laser power and temperature on AS excited ODMR signals, the researchers proved that the AS photoluminescence (PL) was induced by phonon-assisted single photon absorption process and was applicable to all-optical high-temperature temperature sensing. Based on this, they found that AS and Strokes excited ODMR followed similar […]
Quantum computing with holes
Phys.org June 3, 2021 An international team of researchers (Austria, Italy, Germany, Spain) has created a new candidate system for reliable qubits using the spin of holes which carry the quantum-mechanical property of spin and interact if they come close to each other. The hole can move around in the solid when a neighboring electron fills the hole. They confined the holes to the germanium-rich layer in the middle of layered silicon and germanium adding gates to control the movement of holes. They could move holes and alter their properties. By engineering different hole properties, they created the qubit out […]
Researchers confront major hurdle in quantum computing
Phys.org May 5, 2021 To realize the full potential of quantum computing high-fidelity information transfer mechanisms are required for quantum error correction and efficient algorithms – and that presents a major experimental challenge. A team of researchers in the US (University of Rochester, Virginia Tech, Purdue University) demonstrated adiabatic quantum state transfer (AQT) which is not affected by pulse errors and noise. They exploited entanglement even when the particles are separated by a large distance to transfer one electron’s quantum spin state across a chain of four electrons in semiconductor quantum dots. AQT is robust against pulse errors and noise. […]
New computing algorithms expand the boundaries of a quantum future
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 […]
Qubits composed of holes could be the trick to build faster, larger quantum computers
Phys.org April 2, 2021 Strong spin-orbit interactions make hole quantum dots central for scalable quantum computation. Therefore it is important to establish to what extent spin-orbit coupling exposes qubits to electrical noise, facilitating decoherence. Taking Ge as an example an international team of researchers (Australia, Canada) has shown that group IV gate-defined hole spin qubits generically exhibit optimal operation points, defined by the top gate electric field, at which they are both fast and long-lived: the dephasing rate vanishes to first order in the electric field noise along with all directions in space, the electron dipole spin resonance strength is […]
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 […]
Coding for Qubits: How to Program in Quantum Computer Assembly Language
IEEE Spectrum February 19, 2021 Researchers at Sandia National Laboratory are working on a project to run code provided by academic, commercial, and independent researchers around the world on their “QSCOUT” ( Quantum Scientific Computing Open User Testbed) platform as they steadily upgrade it from 3 qubits today to as many as 32 qubits by 2023. QSCOUT consists of ionized ytterbium atoms levitating inside a vacuum chamber. Flashes of ultraviolet laser light spin these atoms about, executing algorithms written in the team’s quantum assembly code JAQAL (Just Another Quantum Assembly Language). JACQAL includes commands to initialize the ions as qubits, […]