Nanoearthquakes control spin centers in SiC

Science Daily  September 4, 2020 An international team of researchers (Germany, Russia) demonstrated the use of elastic vibrations to manipulate the spin states of optically active color centers in SiC at room temperature. They used a surface acoustic wave cavity to selectively address spin transitions with magnetic quantum number differences of ±1 and ±2 in the absence of external microwave electromagnetic fields. These spin-acoustic resonances reveal a nontrivial dependence on the static magnetic field orientation, which is attributed to the intrinsic symmetry of the acoustic fields combined with the peculiar properties of a half-integer spin system. These findings establish silicon […]

Cosmic rays may soon stymie quantum computing

MIT News  August 26, 2020 Superconducting qubits are used for high-fidelity operations. However, the density of the broken Cooper pairs, referred to as quasiparticles, is orders of magnitude higher than the value predicted at equilibrium suggesting that another generation mechanism exists. A team of researchers in the US (MIT, Pacific Northwest National Laboratory, MIT Lincoln Laboratory) has provided evidence that ionizing radiation from environmental radioactive materials and cosmic rays contributes to this observed difference. The effect of ionizing radiation leads to an elevated quasiparticle density, which they predict would ultimately limit the coherence times of superconducting qubits. They demonstrated that […]

Scientists strengthen quantum building blocks in milestone critical for scale-up

Phys.org  July 20, 2020 Spin-orbit qubits coherence have shown limited coherence times, far too short for quantum technologies. An international team of researchers (Australia, Japan, Germany) has demonstrated that increasing the strength of that spin-orbit coupling lets us achieve significantly longer coherence times. They showed ultra-long coherence times of 10 ms for holes where spin–orbit coupling yields quantized total angular momentum. They focused on holes bound to boron acceptors in bulk silicon 28, whose wavefunction symmetry can be controlled through crystal strain, allowing direct control over the longitudinal electric dipole that causes decoherence. These results open a pathway to develop new […]

Corralling Groups of Photons

APS Synopsys  July 14, 2020 An international team of researchers (Germany, Spain, Denmark) propose a device to create flocks of photons by sorting a coherent pulse of light into bunches of strongly correlated photons. The device consists of an optical waveguide that is strongly coupled to a row of two-level quantum systems. A laser pulse is shone down the waveguide. Photons within the pulse are strongly connected to each other such that the arrival of one portends the quick arrival of the next. The atoms absorb pulse photons, entering an excited state. If photons connected to the absorbed ones interact […]

A quantum of solid

Science Daily  January 30, 2020 Quantum control of complex objects in the regime of large size and mass provides opportunities for sensing applications and tests of fundamental physics. An international team of researchers (Austria, MIT) has demonstrated a quantum interface that combines optical trapping of solids with cavity-mediated light matter interaction. Precise control over the frequency and position of the trap laser with respect to the optical cavity allows laser-cooling an optically trapped nanoparticle into its quantum ground state of motion from room temperature. The cooling, in combination with optical trap manipulation, may enable otherwise unachievable superposition states involving large […]

The experimental demonstration of a spin quantum heat engine

Phys.org  December 30, 2019 An international team of researchers (Canada, Singapore, Brazil) successfully demonstrated that the proof-of-concept quantum heat engine is able to reach an efficiency for work extraction very close to its thermodynamic limit. They used a nuclear spin placed in a chloroform molecule and nuclear magnetic resonance techniques. They specifically manipulated the nuclear spin of a Carbon 13 isotope using a radiofrequency field, ultimately producing an Otto cycle (i.e., the thermodynamic cycle used in most common motors). They were able to characterize all energy fluctuations in work and heat, besides the irreversibility at the quantum scale…read more. TECHNICAL […]

Structured light promises path to faster, more secure communications

Science Daily  October 29, 2019 Researchers in South Africa review the recent progress in the emergence of a second quantum revolution ushering in control of quantum states, outlining the core concepts in a tutorial manner before delving into the advances made in creation, manipulation, and detection of such quantum states. They cover advances in using orbital angular momentum as well as vectoral states that are hybrid entangled, combining spatial modes with polarization to form an infinite set of two-dimensional spaces: multidimensional entanglement. The authors highlight the work in pushing the boundaries in both the dimension and the photon number, before […]

Physicists couple key components of quantum technologies

EurekAlert  October 9, 2019 Researchers in Germany developed an interface that couples light sources for single photons with nanophotonic networks. They considered quantum emitters which are embedded in nanodiamonds and emit photons when they are stimulated by means of electromagnetic fields. In order to produce the desired interfaces, they aimed to develop optical structures tailored to the wavelength of the quantum emitters. In structuring the crystals, they varied not only the size and the arrangement of the cavities, but also the width of the waveguide on which the cavities were placed. They found photonic crystals which demonstrated a special variation […]

Creating different kinds of light with manipulable quantum properties

Science Daily  September 27, 2019 An international team of researchers (Louisiana State University, NIST, Mexico, Germany) experimentally demonstrated that the manipulation of the quantum electromagnetic fluctuations of two-mode squeezed vacuum states leads to a family of quantum-correlated multiphoton states with tunable mean photon numbers and degree of correlation. The technique relies on the use of conditional measurements to engineer the excitation mode of the field through the simultaneous subtraction of photons from two-mode squeezed vacuum states. They demonstrated the engineering of a quantum state of light with up to ten photons which is an important step towards the generation of […]

Entangling photons generated millions of miles apart

Phys.org  August 28, 2019 An international team of researchers (China, USA – Louisiana State University, Texas A&M University, Baylor University, Princeton University, Germany, UK) conducted an experiment to test quantum interference, entanglement, and nonlocality using two dissimilar photon sources, the Sun and a semiconductor quantum dot on the Earth, which are separated by approximately 150 million km. By making the photons indistinguishable in all degrees of freedom, they observed time-resolved two-photon quantum interference with a raw visibility of 0.796, well above the 0.5 classical limit, providing unambiguous evidence of the quantum nature of thermal light. Using the photons with no […]