Volume 19 Issue 3, March 2023

Bibliometric evaluation causes competition and stalls scientific progress. We need to abandon it and encourage collaboration.

Measurements of charge pumping in a quantum anomalous Hall device demonstrate that quantized Hall conductance does not require an edge to transport current, paving the way for the realization of other exotic electronic behaviour.

In proton–proton collisions, the CMS Collaboration measures the simultaneous production of three particles, each consisting of a charm quark and a charm antiquark, which yields insights into how the proton’s constituents interact.

The discovery of an unexpectedly large thermoelectric response in a 2D material establishes its power to probe the entropy carried by its charge carriers in the hotly debated strange metal phase.

The emission of light from qubits in a superconducting circuit can be controlled in order to choose the direction of the photons’ propagation, which could be used to route information in quantum networks.

The study of complexity of unitary transformations has become central to quantum information theory and, increasingly, quantum field theory and quantum gravity. A proof of how complexity grows with system size demonstrates the power of a geometric approach.

Long-theorized, non-dispersive de Broglie wave packets have been optically synthesized using classically entangled ring-shaped space-time wave packets in a medium exhibiting anomalous dispersion.

Renormalization is a technique based on a repeated coarse-graining procedure used to study scale invariance and criticality in statistical physics. Now, an expansion of the renormalization toolbox allows to explore scale invariance in real-world networks.

Liquid crystal defect structures with topology similar to a Möbius strip can rotate, translate and transform into one another under an applied electric field.

Measurements of the switching supercurrent statistics of a superconducting quantum interference device based on bismuth, a second-order topological insulator, reveal that excited Andreev states are surprisingly long-lived. This protection can be attributed to the splitting of the Andreev pairs carrying the supercurrent along separate crystal hinges of opposite helicities.

The critical temperature of a high-temperature superconductor was systematically tuned using an ionic-liquid gating technique. Measurements of this system revealed a universal quantitative relationship between superconductivity and the strange-metal state, which gives insight into the mechanism responsible for high-temperature superconductivity.

Careful thermal transport measurements identify the topological nature of transverse thermal conductance in the fractional quantum Hall regime.

Quantized charge pumping is a hallmark of topological phases. Now, this effect is observed in the quantum anomalous Hall regime.

The CMS Collaboration reports the study of three simultaneous hard interactions between quarks and gluons in proton–proton collisions. This manifests through the concurrent production of three J/ψ mesons, which consist of a charm-quark–antiquark pair.

Multi-parameter metrology requires collective measurements on more than one copy of the same quantum state. Now, an optimal scheme for the estimation of qubit rotations has been demonstrated on superconducting and trapped-ion platforms.

Second-order topological insulators feature helical one-dimensional states located at crystal hinges. Running a supercurrent through such systems is now shown to lead to long-lived excited Andreev pairs due to their separation along hinges with opposite helicity.

Superconductivity can emerge from a strange-metal state, but the exact relationship between them is unknown. Now, quantitative measurements reveal the dependence of resistivity in the strange metal on the superconducting transition temperature.

Transport measurements between a normal conductor and superconductor show that in this case, the Coulomb drag response can be much larger than that between two normal conductors.

The transport behaviour of strange metals is distinct from weakly interacting Fermi liquids. Now, a large thermoelectric response has been shown at the transition between those two states.

Established methods of controlling silicon spin qubits require high-frequency signals that can be difficult to implement for various reasons. Exploiting the coupling between spin and valley degrees of freedom provides an alternative approach.

Light could be used to carry quantum information in networks, but this requires methods to prepare and control individual photons. A superconducting circuit can controllably emit photons in either direction along a microwave waveguide.

Quantum operations can be considered as points in a high-dimensional space in which distance reflects the similarity of two operations. Applying differential-geometric methods in this picture gives insights into the complexity of quantum systems.

Time-crystalline order appears in periodically driven systems with broken time-translation symmetry. Now, a protocol based on pulse drives of different frequencies is used to create and continuously observe time crystals with long lifetimes.

Sufficient optical gain provided by Yb³⁺ doping allows phonon lasing from a levitated optomechanical system at the microscale, which exhibits strong mechanical amplitudes and nonlinear mechanical harmonics above the lasing threshold.

Interactions between photons arise due to the presence of optical nonlinearities. In topological Thouless pumps, a sufficiently strong nonlinearity leads to soliton transport with a fractionally quantized plateau structure—reminiscent of transport in the fractional quantum Hall effect.

Dispersive coupling between two optical parametric oscillators induces a first-order phase transition in the system at a critical detuning. This manifests as a discontinuity in the dimer’s spectrum, which may be useful for enhanced sensing.

de Broglie–Mackinnon wave packets are an extension of matter waves, but have so far remained a theoretical construct. Combining spatio-temporal light fields with anomalous dispersion has now allowed their experimental observation.

The renormalization group method is routinely employed in studies of criticality in many areas of physics. A framework based on a field theoretical description of information diffusion now extends this tool to the study of complex networks.

Topological defect structures that swim have been realized in liquid crystals. Now, a range of structures with topology reminiscent of a Möbius strip swim and transform into one another.

The nautical mile and knot were acknowledged by the International Bureau of Weights and Measures. Bart Verberck wonders why this is not the case anymore.