Research Briefing in 2023

Neutron spectroscopy, entanglement analysis, and simulations provide evidence that KYbSe₂ closely approximates a 2D quantum spin liquid. Although KYbSe₂ displays magnetic ordering at low temperatures, its magnetic dynamics are dominated by fractionalized excitations that exhibit anomalously large quantum entanglement, indicating that on finite timescales KYbSe₂ exhibits quantum spin liquid physics.

Landau’s theory of Fermi liquids predicts that impurities embedded in a Fermi sea of atoms form quasiparticles called polarons that interact with one another via the surrounding medium. Such mediated polaron–polaron interactions have been directly observed and are shown to depend on the quantum statistics of the impurities.

An approach combining single-cell imaging, agent-based simulations, and continuum mechanics theory is used to observe the effect of environmental stiffness on biofilm development. These measurements indicate that confined biofilms behave as active nematics, in which the internal organization and cell lineage are controlled by the shape and boundary of the biofilm.

Local thermodynamic measurements of a twisted transition metal dichalcogenide heterostructure reveal competition between unconventional charge order and Hofstadter states. This results from the presence of both flat and dispersive electronic bands, whose energetic ordering can be experimentally tuned.

Drops sitting on an array of parallel fibres spontaneously move along the fibres when subject to an airflow perpendicular to the array. The drops show long-range aerodynamic interactions with their downstream and upstream neighbours, and these can catalyse drop coalescence and removal of drops from the fibres — relevant for applications such as fog harvesting and filtration.

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.

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.

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.

A coherent interface between a mechanical oscillator and superconducting electrical circuits would enable the control of quantum states of mechanical motion, but such interfaces often result in excess mechanical energy loss. A new material-agnostic approach is shown to achieve strong electromechanical coupling while preserving a long phonon lifetime.

Repeated firing of vortex rings into a water tank is shown to create an isolated blob of confined turbulence — perfect for studying the nature of turbulence and its interface with quiescence. Moreover, using coherent vortex rings to feed the turbulence allows the controlled injection of conserved quantities such as helicity.

An experimental platform comprising two disordered superconductors separated by a thermally conducting electrical insulator represents a controllable physical system of interdependent networks. This system is modelled by thermally coupled networks of Josephson junctions. This platform could provide insights into theoretical multiscale phenomena, such as cascading tipping points or self-organized branching processes.

It’s a long-standing theoretical prediction that mutual information in locally interacting, many-body quantum systems follows an area law. Using cold-atom quantum-field simulators on an atom chip to measure the scaling of von Neumann entropy and mutual information, that prediction is now proved true.

Time crystals are a new state of matter. Conventional crystal properties are periodic in space, while the properties of a time crystal are periodic in time. A continuous quantum time crystal has recently been realized, and now, using optically driven many-body interactions in a nano-mechanical photonic metamaterial, a classical continuous time crystal has been created.

Photon bound states are quantum states of light that emerge in systems with ultrahigh optical non-linearities. A single artificial atom was used to study the dynamics of these states, revealing that the number of photons within the pulse determines the time delay after the pulse scatters off the atom.

Controlling the spatial distribution of optically active spin defects in solids is a long-standing goal in the quantum sensing and simulation communities. Measurements of the many-body noise generated by the spins were used to verify that a highly coherent and strongly interacting quantum spin system was confined to two dimensions within a diamond substrate.

A DNA-based nanorobotic arm connected to a base plate through a flexible joint can be used to store and release mechanical energy. The joint acts as a torsion spring that is wound up by rotating the arm using external electric fields and is released using a high-frequency electrical pulse.

Coherent multidimensional spectroscopy with nanoscale spatial resolution was used to directly probe a plasmon polariton quantum wave packet. To reproduce these results an improved quantum model of photoemission was required, in which the coherent coupling between plasmons and electrons is accounted for with the plasmon excitations extending beyond a two-level model.

An atomic Bose–Fermi mixture was driven through a quantum phase transition by varying an applied magnetic field to tune the interspecies interactions. This approach enabled the efficient generation of sodium–potassium molecules in the quantum degenerate regime.

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.