The field of active nematics has traditionally employed descriptions based on dipolar activity. However, it is theoretically predicted that interactions with a substrate, prevalent in most biological systems, lead to novel forms of activity, such as quadrupolar activity, that are governed by hydrodynamic screening. Here, combining experiments and numerical simulations, we show that upon light-induced solidification of the underlying medium, microtubule-kinesin mixtures undergo a transformation that leads to a biphasic active suspension. Using an active lyotropic model, we prove that the transition is governed by screening effects that alter the dominant form of active stress. Specifically, the combined effect of friction and quadrupolar activity leads to a hierarchical folding that follows the intrinsic bend instability of the active nematic layer. Our results demonstrate the dynamics of the collapse of orientational order in active nematics and present a new route for controlling active matter by modifying the activity through changing the surrounding environment.

Extracting the rotational energy from a Kerr black hole (BH) is one of the crucial topics in relativistic astrophysics. Here, we give special attention to the Penrose ballistic process based on the fission of a massive particle ${\mu }_0$ into two particles ${\mu }_1$ and ${\mu }_2$, occurring in the ergosphere of a Kerr BH. Bardeen et al. indicated that for the process to occur, some additional “hydrodynamical forces or superstrong radiation reactions” were needed. Wald and Chandrasekhar further expanded this idea. This animosity convinced Piran and collaborators to move from a simple three-body system characterizing the original Penrose process to a many-body system. This many-body approach was further largely expanded by others, some questionable in their validity. Here, we return to the simplest original Penrose process and show that the solution of the equations of motion, imposing the turning point condition on their trajectories, leads to the rotational energy extraction from the BH expected by Penrose. The efficiency of energy extraction by a single process is quantified for three different single decay processes occurring, respectively, at $r=1.2M$, $r=1.5M$, and $r=1.9M$. An interesting repetitive model has been proposed by Misner et al. [Gravitation (W. H. Freeman, San Francisco, 1973)]. Indeed, it would appear that a repetitive sequence of 246 decays of the above injection process at $r=1.2M$ and the corresponding ones at $r=1.5M$ and $r=1.9M$ could extract 100% of the rotational energy of the BH, so violating energy conservation. The accompanying article, accounting for the existence of the BH irreducible mass, introduces a nonlinear approach that avoids violating energy conservation and leads to a new energy extraction process.

Realizing deterministic, high-fidelity entangling interactions—of the kind that can be utilized for efficient quantum information processing—between photons remains an elusive goal. Here, we address this long-standing issue by devising a protocol for creating and manipulating highly entangled superpositions of well-controlled states of light by using an on-chip photonic system that has recently been shown to implement three-dimensional, non-Abelian quantum holonomy. Our calculations indicate that a subset of such entangled superpositions are maximally entangled, “volume-law” states, and that the underlying entanglement can be distilled and purified for applications in quantum science. Crucially, we generalize this approach to demonstrate the potentiality of deterministically entangling two arbitrarily high, $N$-dimensional quantum systems, by formally establishing a deep connection between the matrix representations of the unitary quantum holonomy—within energy-degenerate subspaces in which the total excitation number is conserved—and the ($2j+1$)-dimensional irreducible representations of the rotation operator, where $j=(N-1)/2$ and $N\ge 2$. Specifically, our protocol deterministically entangles spatially localized modes that are not only distinguishable but are also individually accessible and amenable to state preparation and measurement, and therefore, we envisage that this entangling mechanism could be utilized for deterministic quantum information processing with light.

Genuine multipartite nonlocality and nonlocality arising in networks composed of several independent sources have been investigated separately. While some genuinely entangled states cannot be verified by violating a single Bell-type inequality, a quantum network consisting of different sources enables the certification of the nonclassicality of all sources. In this Letter, we propose the first method to verify both types of nonlocality simultaneously in a single experiment. We consider a quantum network comprising a bipartite source and a tripartite source. We demonstrate that there are quantum correlations that cannot be simulated if the tripartite source distributes biseparable systems while the bipartite source distributes even stronger-than-quantum systems. These correlations can be used to verify both the genuine multipartite nonlocality of generalized Greenberger-Horne-Zeilinger states and the full network nonlocality that is stronger than all the existing results. Experimentally, we observe both types of nonlocality in a high-fidelity photonic quantum network by violating a single network Bell inequality.

We report a magneto-optical trap of strontium monohydroxide (SrOH) containing 2000(600) molecules at a temperature of 1.2(3) mK. The lifetime is 91(9) ms, which is limited by decay to optically unaddressed vibrational states. This provides the foundation for future sub-Doppler cooling and optical trapping of SrOH, a polyatomic molecule suited for precision searches for physics beyond the standard model including new CP violating particles and ultralight dark matter. We also identify important features in this system that guide cooling and trapping of complex and heavy polyatomic molecules into the ultracold regime.

We present an experimental study of turbulent Rayleigh-Bénard convection in a cylindrical cell. With the addition of a tiny amount of long-chain polymers, we find, surprisingly, that the large-scale flow structure possesses axisymmetric topologies, rather than the well-known single-roll large-scale circulation (LSC), itself a result of spontaneous symmetry breaking. This symmetry restoration is found to arise from anisotropic suppression of velocity fluctuations, i.e., horizontal rms velocity becomes much less than the vertical one, as compared to the nearly isotropic bulk turbulence in the Newtonian case. This mechanism of symmetry restoration resulting from reduced fluctuations contrasts sharply with known symmetry restorations occurring in nature that usually result from increased thermal fluctuations. We further find that the net energy transfer between mean flow and turbulent fluctuations vanishes for axisymmetric topologies, whereas there is a positive net energy transfer from mean flow to turbulence for the lower-symmetry LSC topology (with or without polymers). A comparison of measured heat transfer efficiency and the large-scale flow topology points to a possible explanation for the original spontaneous symmetry breaking, in that the lower-symmetry LSC provides a higher transport efficiency. The present study provides an example of manipulating large-scale flow structures and their symmetries through small-scale properties, leading ultimately to the manipulation of turbulent transport.

We predict two novel quantum drag effects which can occur in macroscopically quantum coherent Josephson circuits. We demonstrate that biasing one resistively shunted Josephson junction by an external current one can induce a nonzero voltage drop across another such junction capacitively coupled to the first one. This quantum Coulomb drag is caused by cotunneling of magnetic flux quanta across both junctions which remain in the “superconducting” regime. Likewise, Cooper pair cotunneling across a pair of connected in series Josephson junctions in the “insulating” regime is responsible for another—dual—quantum Coulomb drag effect.

We study the Heisenberg $S=1/2$ chain with random ferro- and antiferromagnetic couplings using quantum Monte Carlo simulations at ultra-low temperatures, converging to the ground state. Finite-size scaling of correlation functions and excitation gaps demonstrate an exotic critical state in qualitative agreement with previous strong-disorder renormalization group calculations but with scaling exponents depending on the coupling distribution. We find dual scaling regimes of the transverse correlations versus the distance, with an $L$ independent form $C(r)=r^{-\mu }$ for $r\ll L$ and $C(r,L)=L^{-\eta }f(r/L)$ for $r/L>0$, where $\mu >\eta$ and the scaling function is delivered by our analysis. These results are at variance with previous spin-wave and density-matrix renormalization group calculations, thus highlighting the power of unbiased quantum Monte Carlo simulations.

Hexagonal MnTe is an altermagnetic semiconductor with $g$-wave symmetry of spin polarization in momentum space. In the nonrelativistic limit, this symmetry mandates that electric current flowing in any crystallographic direction is unpolarized. However, here I show that elastic strain is effective in inducing the spin splitting effect in MnTe. For this analysis, a spin-orbit-coupled $\mathbf{k}·\mathbf{p}$ Hamiltonian for the valence band maximum at the A point is derived and fitted to eigenvalues calculated from first principles. The spin splitting angle is calculated using the Boltzmann approach in the relaxation-time approximation. The spin splitting gauge factor exceeds 30 near the valence band maximum. Thus, with suitable substrate engineering, MnTe can be used as an efficient source and detector of spin current in spintronic devices. Proper inclusion of the Rashba-Dresselhaus spin-orbit coupling is crucial for the correct description of the transport properties of MnTe.

For quantum phases of Hamiltonian ground states, the energy gap plays a central role in ensuring the stability of the phase as long as the gap remains finite. We propose Markov length, the length scale at which the quantum conditional mutual information (CMI) decays exponentially, as an equally essential quantity characterizing mixed-state phases and transitions. For a state evolving under a local Lindbladian, we argue that if its Markov length remains finite along the evolution, then it remains in the same phase, meaning there exists another quasilocal Lindbladian evolution that can reverse the former one. We apply this diagnostic to toric code subject to decoherence and show that the Markov length is finite everywhere except at its decodability transition, at which it diverges. CMI in this case can be mapped to the free energy cost of point defects in the random bond Ising model. This implies that the mixed-state phase transition coincides with the decodability transition and also suggests a quasilocal decoding channel.

We introduce an electron-photon exchange-correlation functional for quantum electrodynamical density-functional theory (QEDFT). The approach, photon MBD (pMBD), is inspired by the many-body dispersion (MBD) method for weak intermolecular interactions, which is generalized to include both electronic and photonic (electromagnetic) degrees of freedom on the same footing. We demonstrate that pMBD accurately captures effects that arise in the context of strong light-matter interactions, such as anisotropic electron-photon interactions, beyond single-photon effects, and cavity-modulated van der Waals interactions. Moreover, we show that pMBD is computationally efficient and allows simulations of large complex systems coupled to optical cavities.

Bosonic two-mode squeezed states are paradigmatic entangled Gaussian states that have wide utility in quantum information and metrology. Here, we show that the basic structure of these states can be generalized to arbitrary bipartite quantum systems in a manner that allows simultaneous, Heisenberg-limited estimation of two independent parameters for finite-dimensional systems. Further, we show that these general states can always be stabilized by a relatively simple Markovian dissipative process. In the specific case where the two subsystems are ensembles of two-level atoms or spins, our generalized states define a notion of two-mode spin squeezing that is valid beyond the Gaussian limit and that enables true multiparameter estimation. We discuss how generalized Ramsey measurements allow one to reach the two-parameter quantum Cramér-Rao bound, and how the dissipative preparation scheme is compatible with current experiments.

We analyze the relaxation dynamics in an open system, composed by a quantum gas of bosons in a lattice interacting via both contact and global interactions. We report the onset of periodic oscillations of the atomic coherences exhibiting hallmarks of synchronization after a quantum quench. The dynamical behavior exhibits the many-body collapse and revival of atomic coherences and emerges from the interplay of the quantum dissipative nature of the cavity field and the presence of a (approximate) strong symmetry in the dissipative system. We further show that the approximate symmetry can dynamically self-organize. We argue that the approximate symmetry can be tailored to obtain long-lived coherences. These insights provide a general recipe to engineer the dynamics of globally interacting systems.

The scale-invariant inverse energy cascade is a hallmark of 2D turbulence, with its theoretical energy spectrum observed in both direct numerical simulations (DNS) and laboratory experiments. Under this scale-invariance assumption, the effective diffusivity of a 2D turbulent flow is dimensionally controlled by the energy flux and the friction coefficient only. Surprisingly, however, we show that such scaling predictions are invalidated by numerical solutions of the 2D Navier-Stokes equation forced at intermediate wave number and damped by weak linear or quadratic drag. We derive alternate scaling-laws for the effective diffusivity based on the emergence of intense, isolated vortices causing spatially inhomogeneous frictional dissipation localized within the small vortex cores. The predictions quantitatively match DNS data. This study points to a universal large-scale organization of 2D turbulent flows in physical space, bridging standard 2D Navier-Stokes turbulence with large-scale geophysical turbulence.