天美传媒

Torsional Alfv茅n waves are promising candidates for transporting energy from the solar surface into the corona and have been theoretically predicted for decades. However, their detection is notoriously difficult and so far has mostly relied on indirect signatures.

Imaging and spectral data from the space-based IRIS observatory has been used to study a surge of cool solar plasma in the corona above the East limb of the Sun. The surge has been triggered by the magnetic reconnection of open and closed magnetic fields. Using imaging and spectral information the tell-tale torsional signatures of plasma rotation of alternating sense have been revealed.

This discovery was made by scientists from the 天美传媒's Physics Department and the University of Oslo's Rosseland Centre for Solar Physics and has been published this month as a letter in the journal of Astronomy and Astrophysics. This study provides the first direct observational evidence that magnetic reconnection leads to the generation of large-scale torsional Alfv茅n waves in the solar corona.

Petra Kohutova, Erwin Verwichte, and Clara Froment 2020, A&A, 633, L6

A new defect elimination strategy in highly mismatched heteroepitaxy is demonstrated to achieve ultra-low dislocation density using a highly scalable process.

As the first generation of quantum computers are now reaching the point where they can answer such otherwise impossible questions, it is necessary to consider how the answers of these early devices can be confirmed correct. The full power of quantum computing includes a wide range of problems for which this is not possible, instead demanding new techniques to test quantum computers. A new test has now been proposed by Samuele, Theodoros, and Animesh () which can be used to make sure the quantum computer is working correctly without using excessive additional resources while still testing the entire quantum computer. Published in the , this protocol uses circuits which have the same form as the desired circuit but are formulated to give known outcomes. Based on the accuracy of these circuits they are able to place a statistical bound on how close the distribution the quantum computer gives is to the correct distribution.

New work from the group, now published in , demonstrates that the Holevo Cram茅r-Rao bound, the fundamental limit to how precise any sensor can be, can be evaluated by numerically efficient methods. Computation of the Holevo Cram茅r-Rao bound requires the solving of a non-linear optimisation problem. In this publication Francesco, Jamie, and Animesh demonstrate that the necessary optimisation can be expressed as a convex optimisation problem. This realisation allows efficient numerical evaluation of the Holevo Cram茅r-Rao bound, opening up the possibility of practically applying it in quantum sensing problems.