Volume 19 Issue 10, October 2023

Unsubstantiated claims that fuel growing public concern over the toxicity of photovoltaic modules and their waste are slowing their deployment. Clarifying these issues will help to facilitate the decarbonization that our world depends on.

Efficient superconducting diodes can be designed according to established physics. However, emerging concepts must be united with known mechanisms in order to unlock functionality in rectification and frequency conversion.

Two studies of electrons generated from laser-triggered emitters have found highly predictable electron–electron energy correlations. These studies, at vastly different energy scales, may lead to heralded electron sources, enabling quantum free-electron optics and low-noise, low-damage electron beam lithography and microscopy.

In principle, quantum entanglement gives advantages in radar detection even under noisy and lossy operating conditions. More than a decade after the proposal, the predicted quantum advantage has finally been demonstrated at microwave frequencies.

Exploring the combined effects of many-body interactions and topology is experimentally challenging. Now, researchers have shown that strong interparticle interactions force ultracold atoms to shift as a whole or one by one, or break quantization in a topological pump.

Non-perturbing spectroscopy allows the observation of fragile fractional quantum Hall states and broken symmetries in graphene with atomic precision.

When a system is driven across a second-order phase transition, defects can form because it cannot respond quickly enough to the new conditions. The Kibble–Zurek mechanism explains this physics, and has now been invoked for Ising-type domains.

An experimental approach enables the observation of the microscopic details of the relaxation of a highly equilibrated glass back to the liquid phase in real time. This points to a scenario where devitrification proceeds via localized seeds separated by macroscopic length scales.

Most quantum processors rely on native interactions between pairs of qubits to generate quantum entangling gates. Now, by modulating the driving laser fields, gates that entangle a triplet or quartet of trapped-ion qubits have been realized, creating useful new components for quantum computing applications.

Using ‘momentum cooling’ in cyclotron-based proton therapy can increase proton transmission rates and thereby reduce treatment delivery times. This simple technique, which reduces the momentum spread of the proton beam without introducing substantial beam losses, enhances efficiency and has the potential to reduce costs, thereby advancing cancer treatment and improving patient outcomes.

The collective dynamics observed between Bose-condensed atoms and molecules indicate the occurence of macroscopic quantum phenomena. Experimental investigations found that the atomic and molecular populations oscillate at a frequency that scales with the sample size, providing evidence for bosonic enhancement. These findings could make many-body quantum dynamics accessible in ultracold molecule research.

Even a few electrons confined to a tight space and time interval interact strongly, often causing issues for applications. The resulting repulsion has now been shown to allow strong electron–electron correlations, enabling shot-noise reduction.

Coulomb interactions in free-electron beams are usually seen as an adverse effect. The creation of distinctive number states with one, two, three and four electrons now reveals unexpected opportunities for electron microscopy and lithography from Coulomb correlations.

Proposals for quantum radars have suggested that in noisy environments there may be a benefit in sensing using quantum microwaves. A superconducting circuit experiment has now confirmed an advantage exists under appropriate conditions.

Many quantum devices operate in the microwave regime, but long-distance communication relies on optical photons. A nanomechanical resonator can be used to create entangled optical and microwave photons linking the two frequency regimes.

Across platforms, nonreciprocity requires time-reversal symmetry to be broken. Interference of an excitation-preserving and a non-preserving interaction realizes unidirectional transport in a time-reversal-symmetric system.

In cyclotron-based proton therapy facilities, beam loss due to large momentum spread can limit ultrahigh dose rates. Now, beam transmission is enhanced and higher dose rate is achieved by introducing momentum cooling through a wedge.

Efficient control and measurement of qubits requires them to be strongly coupled to other degrees of freedom, but this can introduce additional decoherence. Now, parametric driving makes it possible to controllably introduce and remove interactions.

Generation of entanglement in quantum computers stems from the native interactions between qubits, which are usually restricted to the pairwise limit. A method to control three- and four-body interactions has now been demonstrated with trapped ions.

Some many-body problems are challenging to solve in real space, but have a convenient Fock-space representation. A superconducting qubit experiment now demonstrates the benefits of this approach for the study of quantum dynamics and criticality.

The study and control of chemical reactions between atoms and molecules at quantum degeneracy is an outstanding problem in quantum chemistry. An experiment now reports the coherent and collective reactions of atomic and molecular Bose–Einstein condensates.

Thouless pumping is the quantization of charge transport through the adiabatic variation of a system’s parameters. The robustness and breakdown of pumping under variations in interparticle interactions have now been shown with ultracold atoms in an optical lattice.

Skyrmions are localized magnetic textures that form lattices in some magnetic materials. Neutron spin-echo measurements have now been able to observe topological effects on the low-energy collective excitations of a skrymion lattice.

A scanning tunnelling microscopy technique that minimally perturbs the sample quantifies the interacting phase diagram of the zeroth Landau level in monolayer graphene.

The Born–Oppenheimer approximation is the prevailing assumption for interpreting ultrafast electron dynamics in solids. Evidence now suggests that collisions between electrons and lattice not captured by this approximation play an important role.

The Kibble–Zurek mechanism is shown to apply to structural Ising domains in three-dimensional materials. Long-range interactions modify the critical exponents away from theoretical predictions.

Precise control of electrons in two-dimensional materials has been limited by fabrication techniques for local gates that introduce disorder. Now, a technique allows patterning of sub-100 nm features and fabrication of very clean interfaces.

Visualizing dynamical changes in glassy systems is challenging because of the time and length scales involved. Now, atomic force microscopy is shown to be a viable method for obtaining a spatio-temporal description of the relaxation of a glass.

Metrology and meteorology: just two letters separating two similar and frequently confused words. Andrea Merlone, Chiara Musacchio and Walter Bich tell us about these different disciplines and ways in which they collaborate.