Letters in 2022

In a plasma-based accelerator, the amplitude of the plasma wave is constrained by the wavebreaking limit. Experiments reveal features of the plasma waves at the point at which wavebreaking occurs.

The study of statistical correlations is central to the description of complex quantum objects. Measurements of density correlation functions of ultracold molecules are now possible through the realization of a molecular quantum gas microscope.

The isotropy of a spherical droplet’s surface causes uniform distribution of adsorbed molecules. However, wrapping the droplet by a crystalline monolayer induces structural defects, enabling temperature-controllable positioning of adsorbates.

The anomalous Hall effect can signify that a material has a spontaneous magnetic order. Now, twisted bilayer graphene shows this effect at half filling, suggesting that the ground state is valley-polarized.

Stacking monolayer WS₂ on top of bilayer WSe₂ creates conditions where electrons and holes can coexist in the structure. Their Coulomb interaction allows them to form bound pairs and hence an excitonic insulator state.

Measurements of four different infinite-layer nickelates show that magnetic behaviour coexists with superconductivity. This is different from what is seen in cuprates, giving a strong distinction between the two classes of oxide superconductors.

Quantum computing with trapped ions requires qubits that can store and manipulate quantum information, and others that can be used for destructive incoherent operations. Different states of ytterbium-171 ions can be used to realize both qubit types

Edge modes in chiral topological systems can carry quantum information without backscattering. A topological lattice of superconducting resonators has been coupled to a qubit, providing a platform for chiral quantum electrodynamics and communication.

Unconventional superconductivity is often associated with the presence of other kinds of electronic order. Observations of charge order in infinite-layer nickelate superconductors show that they fit this pattern.

Qudits are generalizations of qubits that have more than two states, which gives them a performance advantage in some quantum algorithms. The operations needed for a universal qudit processor have now been demonstrated using trapped ions.

Both inter- and intraband transitions contribute to high-harmonic generation in solids, but their exact roles are not fully understood. Experiments with quantum dots show that enhanced intraband transitions lead to increased carrier injection and thus enhanced harmonic generation.

A method to engineer higher-order interactions between photons provides a route to create non-classical and entangled states across multiple modes.

Magnetic skyrmions—a type of localized spin texture—have been theoretically predicted to annihilate with counterparts known as antiskyrmions. By means of electron microscopy, such annihilation has now been observed in a cubic chiral magnet.

Combinatorial optimization is one of the areas for which quantum computing promises to overcome classical devices. An experiment with arrays of Rydberg atoms now shows how to solve combinatorial graph problems with auxiliary atomic wires.

The LHCb Collaboration reports the observation of an exotic, narrow, tetraquark state that contains two charm quarks, an up antiquark and a down antiquark.

The flat portions of the band structure in bilayer graphene are shown to support interaction-driven symmetry-broken states, similar to moiré heterostructures.

Many-body open quantum systems are predicted to undergo a phase transition towards a pure state through frequent projective measurements. The phases separated by this transition have now been observed with random circuits on a trapped-ion computer.

Transport experiments highlight a technique to detect transitions in the topological state of two-dimensional materials, with possible applications in memory devices.

Unless you are nearby, it is difficult to verify where someone is. Access to a single qubit and classical computation and communication makes it possible to securely check someone’s position as long as adversaries’ quantum resources are limited.

Heat transport in electronic systems is influenced by nearby superconductors due to the so-called proximity effect. Combining this with the manipulation of superconductivity using magnetic fields enables the control of nanoscale thermal transport.