We experimentally demonstrate, for the first time, noise diagnostics by repeated quantum measurements, establishing the ability of a single photon subjected to random polarization noise to diagnose non-Markovian temporal correlations of such a noise process. Both the noise spectrum and temporal correlations are diagnosed by probing the photon with frequent (partially) selective polarization measurements. We show that noise with positive temporal correlations corresponds to our single photon undergoing a dynamical regime enabled by the quantum Zeno effect (QZE), whereas noise characterized by negative (anti) correlations corresponds to regimes associated with the anti-Zeno effect (AZE). This is the first step toward a novel noise spectroscopy based on QZE and AZE in single-photon state probing able to extract information on the noise while protecting the probe state, a conceptual paradigm shift with respect to traditional interferometric measurements.

We use hyperentanglement to experimentally realize deterministic entanglement swapping based on quantum elegant joint measurements. These are joint projections of two qubits onto highly symmetric, isoentangled bases. We report measurement fidelities no smaller than 97.4%. We showcase the applications of these measurements by using the entanglement swapping procedure to demonstrate quantum correlations in the form of proof-of-principle violations of both bilocal Bell inequalities and more stringent correlation criteria corresponding to full network nonlocality. Our results are a foray into entangled measurements and nonlocality beyond the paradigmatic Bell state measurement and they show the relevance of more general measurements in entanglement swapping scenarios.

Phase estimation is a quantum algorithm for measuring the eigenvalues of a Hamiltonian. We propose and rigorously analyze a randomized phase estimation algorithm with two distinctive features. First, our algorithm has complexity independent of the number of terms $L$ in the Hamiltonian. Second, unlike previous $L$-independent approaches, such as those based on qDRIFT, all algorithmic errors in our method can be suppressed by collecting more data samples, without increasing the circuit depth.

Proton-proton interactions resulting in final states with two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks ($t$) and Higgs bosons ($H$). The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of $137{\mathrm{fb}}^{-1}$. No significant excess above the background prediction is observed. Upper limits on the branching fractions ($\mathcal{B}$) of the top quark decaying to a Higgs boson and an up ($u$) or charm ($c$) quark are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) 95% confidence level upper limits are found to be 0.019% (0.031%) for $\mathcal{B}(t\to Hu)$ and 0.073% (0.051%) for $\mathcal{B}(t\to Hc)$. These are the strictest upper limits yet determined.

Using 250 neutron star merger simulations with microphysics, we explore for the first time the role of nuclear incompressibility in the prompt collapse threshold for binaries with different mass ratios. We demonstrate that observations of prompt collapse thresholds, either from binaries with two different mass ratios or with one mass ratio but combined with the knowledge of the maximum neutron star mass or compactness, will constrain the incompressibility at the maximum neutron star density $K_{\max }$ to within tens of percent. This otherwise inaccessible measure of $K_{\max }$ can potentially reveal the presence of hyperons or quarks inside neutron stars.

Nonintrusive optical measuring of electric fields in space is crucial for various sciences and technologies. In this study, a simple and highly sensitive optical electric field measurement is demonstrated in high-pressure hydrogen by performing electric-field-induced coherent anti-Stokes Raman scattering (E-CARS) in the visible region. The minimum detectable electric field is $0.5\mathrm{V}/\mathrm{mm}$ at atmospheric pressure. This method does not require excited or atomic species and shows a considerably higher sensitivity than those demonstrated by the commonly applied E-CARS method in the infrared region and electric-field-induced second-harmonic generation. This method can be applied to various Raman-active molecules.

We have demonstrated the resonant control of the elastic scattering cross sections in the vicinity of Feshbach resonances between ${}^{23}\mathrm{Na}{}^{40}\mathrm{K}$ molecules and ${}^{40}\mathrm{K}$ atoms by studying the thermalization between them. The elastic scattering cross sections vary by more than 2 orders of magnitude close to the resonance, and can be well described by an asymmetric Fano profile. The parameters that characterize the magnetically tunable $s$-wave scattering length are determined from the elastic scattering cross sections. The observation of resonantly controlled elastic scattering cross sections opens up the possibility to study strongly interacting atom-molecule mixtures and improve our understanding of the complex atom-molecule Feshbach resonances.

The generation of photon pairs in quantum dots is in its nature deterministic. However, efficient extraction of photon pairs from the high index semiconductor material requires engineering of the photonic environment. We report on a micropillar device with 69.4(10)% efficiency that features broadband operation suitable for extraction of photon pairs. Opposing the approaches that rely solely on Purcell enhancement to realize the enhancement of the extraction efficiency, our solution exploits a suppression of the emission into the modes other than the cavity mode. Furthermore, the design of the device can be further optimized to allow for an extraction efficiency of 85%.

Processes leading to anomalous fluctuations in turbulent flows, referred to as intermittency, are still challenging. We consider cascade trajectories through scales as realizations of a stochastic Langevin process for which multiplicative noise is an intrinsic feature of the turbulent state. The trajectories are conditioned on their entropy exchange. Such selected trajectories concentrate around an optimal path, called instanton, which is the minimum of an effective action. The action is derived from the Langevin equation, estimated from measured data. In particular instantons with negative entropy pinpoint the trajectories responsible for the emergence of non-Gaussian statistics at small scales.

The Kitaev model is a fascinating example of an exactly solvable model displaying a spin-liquid ground state in two dimensions. However, deviations from the original Kitaev model are expected to appear in real materials. In this Letter, we investigate the fate of Kitaev’s spin liquid in the presence of disorder—bond defects or vacancies—for an extended version of the model. Considering static flux backgrounds, we observe a power-law divergence in the low-energy limit of the density of states with a nonuniversal exponent. We link this power-law distribution of energy scales to weakly coupled droplets inside the bulk, in an uncanny similarity to the Griffiths phase often present in the vicinity of disordered quantum phase transitions. If time-reversal symmetry is broken, we find that power-law singularities are tied to the destruction of the topological phase of the Kitaev model in the presence of bond disorder alone. However, there is a transition from this topologically trivial phase with power-law singularities to a topologically nontrivial one for weak to moderate site dilution. Therefore, diluted Kitaev materials are potential candidates to host Kitaev’s chiral spin-liquid phase.

We propose to directly and quantum-coherently couple a superconducting transmon qubit to magnons—the quanta of the collective spin excitations, in a nearby magnetic particle. The magnet’s stray field couples to the qubit via a superconducting quantum interference device. We predict a resonant magnon-qubit exchange and a nonlinear radiation-pressure interaction that are both stronger than dissipation rates and tunable by an external flux bias. We additionally demonstrate a quantum control scheme that generates magnon-qubit entanglement and magnonic Schrödinger cat states with high fidelity.

Recent experiments have demonstrated the possibility of inducing superconducting pairing into counterpropagating fractional quantum Hall edge modes. This paves the way for the realization of localized parafermionic modes, non-Abelian anyons that share fractional charges in a nonlocal way. We show that, for a pair of isolated parafermions, this joint degree of freedom can be read by conductance measurements across standard metallic electrodes. We propose two complementary setups. We investigate first the transport through a grounded superconductor hosting two interacting parafermions. In the low-energy limit, its conductance peaks reveal their shared fractional charge yielding a three-state telegraph noise for weak quasiparticle poisoning. We then examine the two-terminal electron conductance of a blockaded fractional topological superconductor, which displays a characteristic $e/3$ periodicity of its zero-bias peaks in the deep topological regime, thus signaling the presence of parafermionic modes.

Accelerating supermassive black holes, connected to cosmic strings, could contribute to structure formation and get captured by galaxies if their velocities are small. This would mean that the acceleration of these black holes is small, too. Such a slow acceleration has no significant effect on the shadow of such supermassive black holes. We also show that, for slowly accelerating black holes, the angular position of images in the gravitational lensing effects does not change significantly. We propose a method to observe the acceleration of these black holes through gravitational lensing. The method is based on the observation that differential time delays associated with the images are substantially different with respect to the case of nonaccelerating black holes.

Modified gravity theories can accommodate exact solutions, for which the metric has the same form as the one in general relativity, i.e., stealth solutions. One problem with these stealth solutions is that perturbations around them exhibit strong coupling when the solutions are realized in degenerate higher-order scalar-tensor theories. We show that the strong coupling problem can be circumvented in the framework of the so-called U-DHOST theories, in which the degeneracy is partially broken in such a way that higher-derivative terms are degenerate only in the unitary gauge. In this sense, the scordatura effect is built-in in U-DHOST theories in general. There is an apparent Ostrogradsky mode in U-DHOST theories, but it does not propagate as it satisfies a three-dimensional elliptic differential equation on a spacelike hypersurface. We also clarify how this nonpropagating mode, i.e., the “shadowy” mode shows up at the nonlinear level.

The doubly charm tetraquark with flavor $cc\overline{u}$$\overline{d}$ and isospin $I=0$ is investigated by calculating the $D{D}^{*}$ scattering amplitude with lattice QCD. The simulation is done on CLS ensembles with dynamical $u/d$, $s$ quarks and $m_{\pi }\simeq 280\mathrm{MeV}$ for two charm quark masses, one slightly larger and one slightly lower than the physical value. The scattering amplitudes for partial waves $l=0$, 1 are extracted near threshold via the Lüscher method by considering systems with total momenta $PL/(2\pi )=0,1,\sqrt{2},2$ on two spatial volumes. A virtual bound state pole in the $D{D}^{*}$ scattering amplitude with $l=0$ is found ${9.9}_{-7.1}^{+3.6}\mathrm{MeV}$ below the $D{D}^{*}$ threshold for the charm quark mass closer to the physical value. This pole is likely related to the doubly charm tetraquark discovered by LHCb less than 1 MeV below the $D^0{D}^{*+}$ threshold. Future lattice simulations closer to the continuum limit and physical quark masses would be valuable to establish this connection systematically.

How are nuclear quantum fluctuations affecting the properties of dense hydrogen approaching metallization? We report here Raman spectroscopy and synchrotron infrared absorption measurements on deuterium up to 460 GPa at 80 K. By comparing to a previous similar study on hydrogen, isotopic effects on the electronic and vibrational properties in phase III are disclosed. Also, evidence of a probable transition to metal deuterium is observed, shifted by about 35 GPa compared to that in hydrogen. Advanced calculations, quantifying a reduction of the band gap caused by nuclear quantum fluctuations, are compared to the present data.

Single-pulse switching has been experimentally demonstrated in ferrimagnetic GdFeCo and ${\mathrm{Mn}}_2{\mathrm{Ru}}_x\mathrm{Ga}$ alloys. Complete understanding of single-pulse switching is missing due to the lack of an established theory accurately describing the transition to the nonequilibrium reversal path induced by femtosecond laser photoexcitation. In this work, we present general macroscopic theory for the magnetization dynamics of ferrimagnetic materials upon femtosecond laser excitation. Our theory reproduces quantitatively all stages of the switching process observed in experiments. We directly compare our theory to computer simulations using atomistic spin dynamics methods for both GdFeCo and ${\mathrm{Mn}}_2{\mathrm{Ru}}_x\mathrm{Ga}$ alloys. We provide explicit expressions for the magnetization relaxation rates in terms of microscopic parameters, which allows us to propose universal criteria for switching in ferrimagnets.

Feshbach resonances provide an invaluable tool in atomic physics, enabling precise control of interactions and the preparation of complex quantum phases of matter. Here, we theoretically analyze a solid-state analog of a Feshbach resonance in two dimensional semiconductor heterostructures. In the presence of interlayer electron tunneling, the scattering of excitons and electrons occupying different layers can be resonantly enhanced by tuning an applied electric field. The emergence of an interlayer Feshbach molecule modifies the optical excitation spectrum, and can be understood in terms of Fermi polaron formation. We discuss potential implications for the realization of correlated Bose-Fermi mixtures in bilayer semiconductors.