Volume 17 Issue 8, August 2021

The United Nations Sustainable Development Goals outline a roadmap towards a more equitable future for humanity. Along with other scientists, physicists have long made valuable contributions to this endeavour.

High-order harmonics of laser pulses yield spectral components with shorter wavelength and duration and tighter focus than the original pulse. Precise spatiotemporal characterization of this radiation from a relativistic plasma mirror is relevant for ultrafast science.

Quantum gates on trapped ions may be quicker and more reliable owing to squeezing of their vibrational motion. A threefold drop in operation time shows potential for applications in quantum technologies.

A life-or-death choice determines the fate of reproductive cells. It has long been assumed that the choice is genetically regulated, but it now seems that the decision may instead be controlled by intracellular pressure.

On the face of it, characterizing quantum dynamics in the exponentially large Hilbert space of a many-body system might require prohibitively many experiments. In fact, the locality of physical interactions means that it can be done efficiently.

A type of polar self-propelled particle generates a torque that makes it naturally drawn to higher-density areas. The collective behaviour this induces in assemblies of particles constitutes a new form of phase separation in active fluids.

Light pulses transiently change a metal to an insulator by unveiling a hidden ordered state.

Using pressure to tune the balance of interactions in a new class of kagome superconductor results in a surprising competition between states — and hints at an unusual, electronically intertwined order.

Isotope ratio measurements are complicated by the instabilities of composition in reference samples. Now a calibration-free method relying on infrared spectroscopy provides measurements that are traceable to International System of Units standards.

In general, it isn’t known when a quantum computer will have an advantage over a classical device. Now it’s proven that computers with limited working memory are more powerful if they are quantum.

Many applications of quantum systems require them to be joined by strong, controllable interactions. Exploiting the physics of quantum squeezing can amplify the strength of boson-mediated interactions, yielding higher performance.

The interplay of superconductivity and nematicity of electrons remains unclear in a wide range of materials. Now, more evidence emerges that nematic fluctuations can be pinned into a static phase by disorder, which hinders the superconductivity.

Ultrafast optical excitation of a charge density wave leads to the formation of a metastable gapped state that synchronizes with the underlying correlated phase.

Transport measurements on the Kitaev quantum spin liquid candidate α-RuCl3 subjected to a magnetic field reveal oscillating behaviour in its thermal conductivity, reminiscent of Shubnikov de Haas oscillations in metals.

During the early development of an organism, some cells are fated to grow while other seemingly healthy cells die. Experiments and theory now reveal that a hydraulic instability is the key to this decision.

Microswimmers tend to accumulate in regions where their speed is significantly reduced, but experimental and numerical evidence now points towards a viscophobic turning mechanism that biases certain microalgae away from high-viscosity areas.

Learning the Hamiltonian of a complex many-body system is hard, but now there is proof that it can be done in a way where the number of required measurements scales as a polynomial of the number of particles.

Entanglement is central to theories of quantum many-body systems but is very resource intensive to measure. A protocol based on a quasilocal parametrization of physical states allows entanglement structures to be studied using very few measurements.

Chains of magnetic atoms on the surface of a superconductor are shown to have topologically non-trivial bands that could host Majorana bound states.

A two-fold rotational symmetry is observed in the superconducting state of NbSe₂. This is strikingly different from the three-fold symmetry of the lattice, and suggests that a mixed conventional and unconventional order parameter exists in this material.

Alkali metals at high pressures have a liquid–liquid transition that is difficult to study in detail. Numerical calculations now suggest that the higher-pressure state is an electride liquid, in which electrons behave like localized anions.

Self-propelled particles are shown to orient themselves towards areas of high density, phase separating into fluid-like clusters. This behaviour is unique to active systems, forming a distinct class of motility-induced phase separation.

Relativistic mirrors are a promising tool to reach laser intensities up to the Schwinger limit. Such a mirror is created in ultra-intense laser–solid interactions, and its temporal and spatial effects on the reflected laser beam are characterized.

The unit length of DNA is a base pair, which serves as a ruler for DNA compaction and processing, as Michelle Wang explains.