Volume 17 Issue 11, November 2021

Having long played the role of collaborators with other, more renowned, institutions, historically disadvantaged South African universities are now challenging the status quo — and emerging as leaders.

Molecular spin qubits that can be controlled electrically are typically susceptible to decoherence. Holmium molecular spins provide a solution by combining robust coherence with strong spin–electric coupling.

Active matter can have macroscopic properties that defy the usual laws of hydrodynamics. Now these tell-tale properties have been traced down to the non-equilibrium character and handedness of interactions between individual particles.

At high pressure and temperature, water forms two crystalline phases, known as hot ‘black’ ices due to their partial opaqueness. A detailed characterization of these phases may explain magnetic field formation in giant icy planets like Neptune.

Precise measurements of the annihilation of an electron–positron pair into a neutron–antineutron pair allow us to take a look inside the neutron to better understand its complex structure.

It has long been assumed that the quantum statistics of light are preserved when photons interact with plasmons. An analysis of the scattering process shows that this is not always the case, as light can mix and match different plasmonic pathways.

Form factors encode the structure of nucleons. Measurements from electron–positron annihilation at BESIII reveal an oscillating behaviour of the neutron electromagnetic form factor, and clarify a long-standing photon–nucleon interaction puzzle.

Through chemical design, the spins in molecular nanomagnets may be used as electrically tunable qubits. Electrical control of molecular distortion enables manipulation of the quantum spin state while suppressing decoherence from magnetic fields.

In addition to the broken time-reversal symmetry that typifies Chern insulators, twisted bilayer graphene hosts a set of topological states with broken translational symmetry.

When interactions between electrons in a material are strong, they can start to behave hydrodynamically. Spatially resolved imaging of current flow in a three-dimensional material suggests that electron–electron interactions are mediated by phonons.

Current quantum computers do not have error correction, which means noise may prevent them outperforming classical devices in useful tasks. An analysis of quantum optimization shows that current noise levels are too high to produce a quantum advantage.

Superionic water is believed to exist in the interior of ice giant planets. By combining machine learning and free-energy methods, the phase behaviours of water at the extreme pressures and temperatures prevalent in such planets are predicted.

Measurements of the phase diagram of water reveal first-order phase transitions to face- and body-centred cubic superionic ice phases. The former is suggested to be present in the interior of ice giant planets.

Non-Abelian topology allows topological charges in multi-gap systems to be converted by braiding of different band nodes. Such multi-gap effects are experimentally observed in an acoustic semimetal.

Atoms in a semiconductor can have non-zero nuclear spins, creating a large ensemble with many quantum degrees of freedom. An electron spin coupled to the nuclei of a semiconductor quantum dot can witness the creation of entanglement within the ensemble.

A state that breaks time-reversal symmetry is observed in the normal phase above the superconducting critical temperature in a multiband superconductor. This could be explained by correlations between the Cooper pairs formed in different bands.

Active fluids exhibit properties reminiscent of equilibrium systems when their degrees of freedom are statistically decoupled. A theory for the fluctuating hydrodynamics of these fluids offers a probe of their anomalous transport coefficients.

The cell cortex stiffens during cell division, facilitating the necessary shape changes. Microrheology measurements now reveal that the rest of the cell interior actually softens, in a process that probably involves two key biomolecules trading roles.

The laws governing electrolysis developed by Michael Faraday, who originally trained as a bookbinder, led to the determination of the Faraday constant, as Daren Caruana recounts.