Active fluids made of powered suspended entities spontaneously give rise to patterns and flows. Yet, how the swimmers activity can be harnessed by external cues into coherent macroscopic flows remains a question of biological and applied relevance. Here, we use magnetotactic bacteria, which respond both to chemical and magnetic signals, to control the onset of global scale shear flows. Shaping positional and orientational orders with external fields allows the force dipoles of each swimmer to combine into a finite active stress. Incorporated in a magnetoactive model, this driving contribution quantitatively captures the observed flows in steady state, while the time-dependent response to rotating fields unveils additional complexity.

The theory of quantum states over time extends the density operator formalism into the temporal domain, providing a unified treatment of timelike and spacelike separated systems in quantum theory. Although recent results have characterized quantum states over time involving two timelike separated systems, it remains unclear how to consistently extend the notion of quantum states over time to multipartite temporal scenarios, such as those considered in studies of Leggett-Garg inequalities. In this Letter, we show that two simple assumptions uniquely single out the Markovian multipartite extension of bipartite quantum states over time, namely, linearity in the initial state and a quantum analog of conditionability for multipartite probability distributions. As a direct consequence of our result, we establish a canonical correspondence between multipartite quantum states over time and Kirkwood-Dirac type quasiprobability distributions, which we show opens up the possibility of experimentally verifying the temporal correlations encoded in quantum states over time via the recent experimental technique of simulating quasiprobability known as quantum snapshotting.

Recent developments have revealed deterministic and exact protocols for performing complex conjugation, inversion, and transposition of a general $d$-dimensional unknown unitary operation using a finite number of queries to a black-box unitary operation. In this Letter, we establish analytical lower bounds for the query complexity of unitary inversion, transposition, and complex conjugation, which hold even if the input unitary is an unknown logarithmic-depth unitary. Specifically, our lower bound of $d^2$ for unitary inversion demonstrates the asymptotic optimality of the deterministic exact inversion protocol, which operates with $O(d^2)$ queries. We introduce a novel framework utilizing differentiation to derive these lower bounds on query complexity for general differentiable functions $f:\mathrm{SU}(d)\to \mathrm{SU}(d)$. As a corollary, we prove that a catalytic protocol—a new concept recently noted in the study of exact unitary inversion—is impossible for unitary complex conjugation. Furthermore, we extend our framework to the partially known setting, where the input unitary operation is promised to be within a subgroup of $\mathrm{SU}(d)$ and the probabilistic setting, where transformations succeed probabilistically.

A first search for beyond the standard model physics in jet multiplicity patterns of multilepton events is presented, using a data sample corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$ of 13 TeV proton-proton collisions recorded by the CMS detector at the LHC. The search uses observed jet multiplicity distributions in one-, two-, and four-lepton events to explore possible enhancements in jet production rate in three-lepton events with and without bottom quarks. The data are found to be consistent with the standard model expectation. The results are interpreted in terms of supersymmetric production of electroweak chargino-neutralino superpartners with cascade decays terminating in prompt hadronic $R$-parity violating interactions.

Accessing coherences is key to fully understand and control ultrafast dynamics of complex quantum systems like molecules. Most photochemical processes are mediated by conical intersections, which generate coherences between electronic states in molecules. We show with accurate calculations performed on gas-phase methyl iodide that electronic coherences of spin-orbit-split states persist in atomic iodine after dissociation. Our simulation predicts a maximum magnitude of vibronic coherence in the molecular regime of 0.75% of the initially photoexcited state population. Upon dissociation, one-third of this coherence magnitude is transferred to a long-lived atomic coherence where vibrational decoherence can no longer occur. To trace these dynamics, we propose a tabletop experimental approach—heterodyned attosecond four-wave-mixing spectroscopy. This technique can temporally resolve small electronic coherence magnitudes and reconstruct the full complex coherence function via phase cycling. Hence, heterodyned attosecond four-wave-mixing spectroscopy leads the way to a complete understanding and optimal control of spin-orbit-coupled electronic states in photochemistry.

Relaxed quantum systems with conservation laws are believed to be approximated by the generalized Gibbs ensemble (GGE), which incorporates the constraints of certain conserved quantities serving as integrals of motion. By drawing an analogy between eigenstate reduced density matrix and GGE, we conjecture that a natural set of conserved quantities for GGE can emerge from the reduced density matrices of properly chosen eigenstates by the entanglement Hamiltonian superdensity matrix (EHSM) framework, and we demonstrate this explicitly for models mappable to free fermions. The framework proposes that such conserved quantities are linear superpositions of eigenstate entanglement Hamiltonians of a larger auxiliary system, where the eigenstates are Fock states occupying what we call the common eigenmodes, which remain eigenmodes when truncated within the physical subsystem. For 1D homogeneous free fermions with (anti)periodic boundary conditions, which maps to 1D hardcore bosons with nearest neighbor hoppings, these conserved quantities lead to a non-Abelian GGE, which predicts the relaxation of both fermion and boson bilinears more accurately than the conventional Abelian GGE. Generalization of this framework may provide novel numerical insights for quantum integrability.

We demonstrate an optimal quantum control strategy for the deterministic preparation of entangled harmonic oscillator states in trapped ions. The protocol employs dynamical phase modulation of laser-driven Jaynes-Cummings and anti-Jaynes-Cummings interactions. We prepare two-mode squeezed vacuum states in the motions of a trapped ion and characterize the states with phase-space tomography. We verify continuous-variable entanglement by measuring an Einstein-Podolsky-Rosen entanglement parameter of 0.0132(7), which surpasses the threshold of 0.25 for Reid’s Einstein-Podolsky-Rosen criterion. We also perform a continuous-variable Bell test and find a violation of the Clauser-Horne-Shimony-Holt inequality, measuring 2.26(3), exceeding the entanglement threshold of 2. We also demonstrate the flexibility of our method by preparing a non-Gaussian entangled oscillator state—a superposition of two-mode squeezed vacuum states.

High-temperature superconductivity in pressurized and strained bilayer nickelates ${(\mathrm{La},\mathrm{Pr})}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ has emerged as a new frontier. One of the key unresolved issues concerns the fermiology that underlies superconductivity. On both theoretical and experimental sides, no general consensus has been reached, and conflicting results exist regarding whether the relevant Fermi surface involves a $\gamma$ pocket—a hole pocket with $d_{z^2}$-orbital character centered at the Brillouin zone corner. Here, we address this issue by unveiling a Janus-faced role of the $\gamma$ pocket in spin-fluctuation-mediated superconductivity. We show that this pocket simultaneously induces dominant pair-breaking and pair-forming channels for the leading $s_{\pm }$-wave pairing. Consequently, an optimal superconducting transition temperature $T_{\mathrm{c}}$ is achieved when the $\gamma$ pocket surfaces at the Fermi level, placing the system near a Lifshitz transition. This suggests that superconductivity can emerge, provided the maximum energy level of the $\gamma$ pocket lies sufficiently close to the Fermi level, either from below or above. Our finding not only reconciles two opposing viewpoints on the fermiology, but also naturally explains recent experiments on ${(\mathrm{La},\mathrm{Pr})}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ thin films, including the superconductivity under compressive strain, two conflicting measurements on the Fermi surface, and the dome shape of $T_{\mathrm{c}}$ as a function of hole doping.

Motivated by the fact that the measured critical field $H_{c2}$ in various transition metal dichalcogenide superconductors is poorly understood, we reexamine its scaling behavior with temperature and spin-orbit coupling (SOC). By computing the spin-susceptibility in a multipocket system, we find that segments of the Fermi surface (FS) at which the SOC has nodal points can have a contribution orders of magnitude larger than the remaining FS, hence setting the $H_{c2}$, assuming the presence of a conventional singlet superconducting order parameter. Nodal lines of an Ising SOC in the Brillouin zone are imposed by symmetry, so they cause such nodal points whenever they intersect an FS pocket, which is indeed the case in monolayer ${\mathrm{NbSe}}_2$ and ${\mathrm{TaS}}_2$, but not in gated ${\mathrm{MoS}}_2$ and ${\mathrm{WS}}_2$. Our analysis reinterprets existing measurements, concluding that a dominant singlet-order parameter on pockets with SOC nodes is consistent with the $H_{c2}(T)$ data for all monolayer Ising superconductors, in contrast to previous contradictory pairing assumptions. Finally, we predict a doping-dependent experimental signature of our theory.

Hydrodynamic electron transport in solids, governed by momentum-conserving electron-electron collisions, offers a unique framework to explore collective phenomena. Within this framework, correlated electron motion is modeled as viscous fluid flow, with viscosity serving as the interaction parameter. Advances in electron hydrodynamics remain constrained by two unresolved issues: the questionable existence of materials with intrinsically smooth boundaries enabling perfect slip in electron fluids and the lack of quantitative experimental confirmation of the theoretical relation linking the viscosity to electron-electron scattering length. Here, we resolve this through measurements of these quantities in the same electron system in $\mathrm{GaAs}/\mathrm{AlGaAs}$ heterostructure. Our experiments reveal large flow slippage at boundaries of microscale constrictions—an unexpected phenomenon for electron liquid that parallels ultrafast water transport in carbon nanotubes. These findings bridge the fields of electron hydrodynamics and nanofluidics, highlighting the transformative potential of hydrodynamic engineering across condensed matter and fluidic technologies.

Reduced basis methods provide an efficient way of mapping out phase diagrams of strongly correlated many-body quantum systems. The method relies on using the exact solutions at select parameter values to construct a low-dimensional basis from which observables can be efficiently and reliably computed throughout the parameter space. Here, we show that this method can be generalized to driven-dissipative Markovian systems, allowing efficient calculations of observables in the transient and steady states. A subsequent distillation of the reduced basis vectors according to their explained variances allows for an unbiased exploration of the most pronounced parameter dependencies indicative of phase boundaries in the thermodynamic limit.

Using thermal tensor-network approach, we investigate the spin Seebeck effect (SSE) of the triangular lattice quantum antiferromagnet hosting spin supersolid phase. We focus on the low-temperature scaling behaviors of the normalized spin current across the interface. For the 1D Heisenberg chain, we find a negative spinon spin current in the bulk with algebraic temperature scaling; at low fields, boundary effects induce a second sign reversal at lower temperatures. These benchmark results are consistent with field-theoretical analysis. On the triangular lattice, spin frustration dramatically enhances the low-temperature SSE, with distinct spin-current signatures—particularly the sign reversal and characteristic temperature dependence—distinguishing different spin states. Remarkably, we discover a persistent, negative spin current in the spin supersolid phase, which saturates to a nonzero value in the low-temperature limit and can be ascribed to the Goldstone-mode-mediated spin supercurrent. Moreover, a universal scaling $T^{d/z}$ is found at the U(1)-symmetric polarization quantum critical points. These distinct quantum spin transport traits provide sensitive spin current probes for spin supersolid states in quantum magnets such as ${\mathrm{Na}}_2\mathrm{BaCo}({\mathrm{PO}}_4{)}_2$. Furthermore, our results also establish spin supersolids as a promising quantum platform for spin caloritronics in the ultralow-temperature regime.

Nonequilibrium current fluctuations represent one of the central topics in nonequilibrium physics. The thermodynamic uncertainty relation (TUR) is widely acclaimed for rigorously establishing a lower bound on current fluctuations, expressed in terms of the entropy production rate and the average current. In this Letter, we focus on an upper bound for the fluctuations, referred to as the inverse thermodynamic uncertainty relation (iTUR). We derive a universal iTUR expression in terms of the entropy production rate for continuous-variable systems governed by overdamped Langevin equations, as well as for discrete-variable systems described by Markov jump processes. The iTUR establishes a no-go theorem prohibiting perpetual superdiffusion in systems with a finite entropy production rate and a finite spectral gap. The divergence of the variance of any current becomes possible only when the spectral gap of the symmetrized time-evolution operator closes or the entropy production rate diverges. As a relevant experimental scenario, we apply the iTUR to the phenomenon of giant diffusion, emphasizing the pivotal roles of the spectral gap and entropy production.

A quantum system with a tunable bath temperature provides an additional degree of freedom for quantum simulators. Such a system can be realized by parametrically modulating the coupling between the system and the bath. Here, by coupling a transmon qubit to a lossy superconducting nonlinear asymmetric inductive element (SNAIL) mode, we experimentally create a tunable bath for the qubit mode. The effective temperature of this bath can be precisely controlled, ranging from negative to positive values. We show that the qubit can be thermalized to equilibrium with different population distributions under different parametric pumping conditions. We further extend our method to the third level of the transmon, demonstrating its potential utility beyond the two-level case. Our results provide a useful tool that can be readily integrated with quantum simulators that would benefit from a nontrivial photon population distribution.

The standard model (SM) of particle physics effectively explains most observed phenomena, though some anomalies, especially in the neutrino sector, suggest the need for extensions. In this Letter, we perform the first global fit of elastic neutrino-nucleus and neutrino-electron scattering data to further test the SM within a consistent framework. Our results on the neutrino charge radius, the only nonzero electromagnetic property of neutrinos in the SM, show no significant deviation, indicating no large beyond the SM flavor-dependent effects for electron and muon neutrinos. By incorporating solar neutrino data from dark matter direct detection experiments, we also place the most stringent constraints on the tau neutrino charge radius obtained from neutrino scattering experiments. Additionally, we determine updated constraints on the vector and axial-vector neutrino-electron neutral current couplings, adjusting for flavor-dependent effects and for the different experimental momentum transfers. The global analysis reveals two allowed solutions: one close to the SM prediction, and a degenerate solution that is favored. We show that future dark matter detectors could achieve sufficient precision to resolve the degeneracy. As we move toward the precision era, this Letter demonstrates the crucial need to properly account for flavor- and momentum-dependent effects to avoid misinterpretations of the data.