Research articles

Topological terms arise naturally in gauge theories but have been difficult to implement in quantum simulators. Now, a tunable topological θ-angle is demonstrated with a cold-atom platform.

The phonon density of states in diamond is engineered using phononic crystals to suppress single-phonon processes that induce decoherence in individual quantum emitters.

Measurements combined with post-processing of their outcomes can be used to prepare ordered quantum states. It has been shown that they can drive a Nishimori phase transition into a disordered state even in the presence of quantum errors.

Quantum fluctuations in frustrated magnets are expected to produce unconventional emergent behaviour. Neutron spectroscopy measurements now provide evidence for emergent gauge fields in a pyrochlore spin ice.

Coupling semiconductor spin qubits over long distances using a superconducting resonator makes different quantum architectures possible. Now, the coherent swapping of quantum states has been observed between qubits coupled using this design.

Measurements of the spin susceptibility in a model cuprate reveal the presence of two distinct gaps underlying the pseudogap behaviour. One gap is attributed to charge density waves and the other to the predicted formation of spin singlets.

Josephson junctions are expected to transition from superconducting to insulating behaviour depending on the impedance of their environment. This Schmid–Bulgadaev transition has now been observed by probing the effect of a junction on its environment.

Tracking ultrafast electronic changes in molecules is challenging, especially in liquids. An X-ray spectroscopy study in pyrazine now shows electronic dynamics created at conical intersections that are rapidly suppressed when the molecule is in water.

Experiments that directly probe the quantum geometric tensor in solids have not been reported. Now, the quantum metric and spin Berry curvature—dual components of the quantum geometric tensor—have been simultaneously measured in reciprocal space.

Experiments on cooperative radiative decay typically involve rapidly escaping photons. Collective emission dynamics have now been studied in an array of quantum emitters interacting via atomic matter waves in a novel regime of slow propagation.

Superconductivity that is mediated by fluctuations of a nematic electronic order has not been experimentally demonstrated. Now an analysis of the symmetry of the superconducting gap in doped FeSe provides evidence of this phenomenon.

Waveguides—often based on total internal reflection—underpin many photonic technologies, including fibre networks for broadband communications. Now a different type of waveguide based on physical diffusion in a scattering medium is demonstrated.

Extending topological braids of complex energy bands to non-Hermitian systems of magnons—the quanta of spin waves—is a crucial step in the development of spin-based topological devices. This has now been experimentally demonstrated.

Arrays of superconducting transmon qubits can be used to study the Bose–Hubbard model. Synthetic electromagnetic fields have now been added to this analogue quantum simulation platform.

The ground state of charge-neutral bilayer graphene in a strong magnetic field is not fully determined. Now thermal transport measurements show an absence of heat flow through that state, suggesting that its collective excitations could be gapped.

Charge-neutral graphene in the quantum Hall regime is known to be an insulator. Now thermal transport measurements show that it also does not conduct heat. This sheds light on the nature of the ground state in this regime.

Different facets of an orthorhombic substrate can stabilize different ordering patterns in a perovskite oxide, even in the absence of differences in strain and polarity mismatches.

The suppression of edge-localized modes in tokamak plasmas is crucial to prevent them from damaging the walls of the chamber. Now experiments confirm the role that magnetic islands play in suppressing these detrimental modes.

Current methods for directly cooling atomic gases to quantum degeneracy involve time-consuming steps. A method based on electromagnetically induced transparency now achieves quantum degeneracy with a notable reduction in preparation time.

It is difficult to control the geometric phase of particles as they undergo quantum tunnelling. Now tuning of the geometric phase of electron spin is demonstrated in tunnelling in a multilayer van der Waals antiferromagnet.