Articles in 2021

Solid-state sources of entangled photons with tailored properties are key elements for integrated quantum computing. Refractive-index perturbations propagating faster than the speed of light may offer a practical approach for generating entangled photon pairs.

The reliability of quantum computers depends on the correction of noise-induced errors, which requires additional resources. Experiments on superconducting qubits have now demonstrated the capabilities of a less-demanding scheme for error detection.

When crystal defects are present in an ensemble of spinning colloids that induce transverse forces on each other, the defects assemble into grain boundaries that can break the system apart into a set of crystal whorls.

Nonlinear optical effects are by default weak but they can be enhanced by sculpting the resulting spectrally periodic pulses from a fibre laser into an optimal shape.

A semiconductor platform for experimentally investigating the multiorbital Bose–Hubbard model with long-range interactions is demonstrated. The interactions between the excitons are strong enough to reach the Mott insulator regime.

Although it shows promise for applications, non-Abelian braiding is difficult to realize in electronic systems. Its demonstration using acoustic waveguides may provide a useful platform to study non-Abelian physics.

Comparing ways of arranging catalysts in living systems reveals that the reaction- and diffusion-limited regimes require different strategies. The formalism generalizes the Thomson problem of optimizing the configuration of electrons on a sphere.

Despite their relevance for quantum technology, photon-pair sources are difficult to control. A theoretical proposal shows how photon pairs can be created from vacuum fluctuations in time-dependent systems, potentially enabling heralded single-photon frequency combs.

Large-scale quantum computers will manipulate quantum information encoded in error-corrected logical qubits. A complete set of operations has now been realized on a logical qubit with error detection.

The nonlinear optical effects underlying many applications are typically weak, but linear dispersion engineering allows the generation of pulses comprising equidistant frequency components, which enhances the effective nonlinearity.

The addition of transverse forces to an ensemble of colloidal spinners induces the appearance of odd elastic crystals, featuring self-propelled defects that organize the system into a ‘self-kneading’ crystal whorl state.

Magnons are collective spin excitations that can propagate over long distances — an attractive trait for information-transfer technologies — but we need to better understand their thermodynamic properties. A platform using graphene may hold the key.

Cosmic rays flying through superconducting quantum devices create bursts of excitations that destroy qubit coherence. Rapid, spatially resolved measurements of qubit error rates make it possible to observe the evolution of the bursts across a chip.

Accurate measurements of the ohm require high magnetic fields to support the quantum Hall effect. Now, high precision is achieved by using the quantum anomalous Hall effect in a low magnetic field, making the measurement much more accessible.

Although magnons in the quantum Hall regime of graphene have been detected, their thermodynamic properties have not yet been measured. Now, a local probe technique enables the detection of the magnon density and chemical potential.

Topological states that are created from strong electron–electron interactions at half-integer superlattice fillings are observed at zero magnetic field.