Volume 20 Issue 2, February 2024

Quantum hypothesis testing—the task of distinguishing quantum states—enjoys surprisingly deep connections with the theory of entanglement. Recent findings have reopened the biggest questions in hypothesis testing and reversible entanglement manipulation.

Optical atomic clocks are extremely accurate sensors despite the poor use of their resources. A parallel quantum control approach might help to optimize the resources of optical atomic clocks, which could lead to an exponential improvement in their performance.

A promising pathway towards the laser cooling of a molecule containing a radioactive atom has been identified. The unique structure of such a molecule means that it can act as a magnifying lens to probe fundamental physics.

Scalable quantum computers require quantum error-correcting codes that can robustly store information. Exploiting the structure of well-known classical codes may help create more efficient approaches to quantum error correction.

Predicting the large-scale behaviour of complex systems is challenging because of their underlying nonlinear dynamics. Theoretical evidence now verifies that many complex systems can be simplified and still provide an insightful description of the phenomena of interest.

Cells actively rearrange their cytoplasmic machinery to perform diverse functions. Now, friction forces generated between cytoplasmic components provide a physical basis for cell shape change.

Orderly or coherent multicellular flows are fundamental in biology, but their triggers are not understood. In epithelial tissues, the tug-of-war between cells is now shown to lead to intrinsic asymmetric distributions in cell polarities that drive such flows.

In its superconducting state, MoTe₂ displays oscillations arising from an edge supercurrent, and when it is near niobium, there is an incompatibility between electron pairs diffusing from niobium and the pairs intrinsic to MoTe₂. Insight into this competition between pairs is obtained by monitoring the noise spectrum of the MoTe₂ supercurrent oscillations.

Predicting the complex flows that emerge in active fluid networks remains a challenge. A combination of experiments and theory was used to determine the hydraulic laws of active fluids. Analogies with frustrated magnetism and loop models explain the emergent flow patterns that result when active fluids explore pipe networks.

Addressing optical transitions at the level of a single site is crucial to unlock the potential of quantum computers and atomic clocks. A scheme based on atom rearrangement now demonstrates such control with demonstrable metrological benefits.

Measurements of the rovibronic structure of radium monofluoride molecules allow the identification of a laser cooling scheme. This will enable precise tests of fundamental physics, such as searches for parity or time-reversal symmetry violation.

Noise is a fundamental obstacle to the stability of atomic optical clocks. An experiment now realizes the design of a spin-squeezed clock that improves interrogation times and enables direct comparisons of performance between different clocks.

Quantum-correlated photons typically characterize strongly nonlinear quantum emitters. A two-photon correlation spectroscopy method now provides a powerful probe of weakly nonlinear many-body quantum systems.

An error detecting code running on a trapped-ion quantum computer protects expressive circuits of eight logical qubits with a high-fidelity and partially fault-tolerant implementation of a universal gate set.

It has been suggested that Gaussian boson sampling may provide a quantum computational advantage for calculating the vibronic spectra of molecules. Now, an equally efficient classical algorithm has been identified.

Light passing through complex media is subject to scattering processes that mix together different photonic modes. This complexity can be harnessed to implement quantum operations.

External driving of qubits can exploit their nonlinearity to generate different forms of interqubit interactions, broadening the capabilities of the platform.

Large quantum computers will require error correcting codes, but most proposals have prohibitive requirements for overheads in the number of qubits, processing time or both. A way to combine smaller codes now gives a much more efficient protocol.

The key to enhance the output of a thermoelectric device is to be able to regulate the thermoelectric voltage generation. Topological magnet Co₃Sn₂S₂-based devices show the way to achieve that goal.

How superconducting states with different order parameter symmetries can interact with each other is not well understood. Now, the edge mode of a Weyl superconductor serves as a probe for competing condensates.

Thermoelectric measurements show an unusual form of critical behaviour at the superconducting quantum phase transition in monolayer WTe₂.

The Haldane model is a paradigmatic example of topological behaviour but has not previously been implemented in condensed-matter experiments. Now a moiré bilayer is shown to realize this model with the accompanying quantized transport response.

Realizing robust ferromagnetic order in two dimensions is challenging as an underlying crystalline framework is normally required. Now room-temperature ferromagnetism is demonstrated in a two-dimensional honeycomb self-assembly of confined molecules.

Faraday waves are standing waves on the surface of a vibrating liquid. Large-wavelength polygonal Faraday waves are now observed in concave water containers, the dynamics of which bear resemblance to Faraday waves seen in Bose–Einstein condensates.

Although using low-rank matrices is the go-to approach to model the dynamics of complex systems, its validity remains formally unconfirmed. An analysis of random networks and real-world data now sheds light on this low-rank hypothesis and its implications.

Experiments with active colloidal fluids in large-scale hydraulic networks reveal a connection between emergent flows and dynamical spin-ice patterns.

Friction forces at the interface between tissues play a key role in tissue morphogenesis. Now friction at the cellular scale is shown to influence cell shape and cell rearrangements.

Coherent motion of cells plays an important role in morphogenesis. Experiments with cellular rings, supported by numerical simulations, suggest that cell polarity and acto-myosin cables are important factors in the onset of coherence.

Adaptive optics allows scientists to correct for distortions of an image caused by the scattering of light. Anita Chandran illuminates the nature of the technique.