We scrutinize the utility of linear cross-entropy in experimentally investigating measurement-induced phase transitions without requiring any post-selection of quantum trajectories. Two random circuits with the same bulk properties but dissimilar initial conditions produce a linear cross-entropy between their bulk measurement outcome distributions that acts as an order parameter, allowing the determination of whether the system is in a volume-law or area-law phase. Bulk measurements, applied to the volume law phase and in the thermodynamic limit, are unable to distinguish between the two initial states, leading to the conclusion that =1. In the area law phase, the value is strictly less than 1. We demonstrate, through numerical sampling, the accuracy of O(1/√2) trajectories for circuits utilizing Clifford gates. This involves running the first circuit on a quantum simulator without post-selection, and supporting this with a classical simulation of the second circuit. Our results indicate that the measurement-induced phase transitions' signature remains noticeable in intermediate system sizes despite the influence of weak depolarizing noise. Our protocol permits the selection of initial states enabling efficient classical simulation of the classical side, but still presents a classically intractable quantum side.

An associative polymer boasts numerous stickers capable of forming reversible connections. For more than three decades, the consensus view has been that reversible associations reshape the pattern of linear viscoelastic spectra by adding a rubbery plateau to the intermediate frequency range, wherein the associations have not yet relaxed, acting effectively as crosslinks. Novel unentangled associative polymers, designed and synthesized here, exhibit exceptionally high sticker densities, up to eight per Kuhn segment, enabling strong pairwise hydrogen bonding interactions exceeding 20k BT without any microphase separation. Experiments reveal that reversible bonds markedly diminish the pace of polymer dynamics, producing minimal alterations in the appearance of linear viscoelastic spectra. The surprising effect of reversible bonds on the structural relaxation of associative polymers is highlighted by a renormalized Rouse model, used to explain this behavior.

Fermilab's ArgoNeuT experiment presents findings from its quest for heavy QCD axions. Axions, weighty and generated in the NuMI neutrino beam's target and absorber, decay into dimuon pairs that are detectable using the unique strengths of ArgoNeuT and the MINOS near detector. This quest is our focus. This decay channel is inspired by a broad class of heavy QCD axion models, resolving the complexities of the strong CP and axion quality problems with axion masses exceeding the dimuon threshold. At a 95% confidence level, we ascertain new limitations on heavy axions within a previously unstudied mass band of 0.2 to 0.9 GeV, with axion decay constants in the region of tens of TeV.

Swirling polarization textures, known as polar skyrmions, with their particle-like characteristics and topological stability, pave the way for future nanoscale logic and memory. Yet, a full understanding of the procedure for generating ordered polar skyrmion lattice formations, and the corresponding responses to applied electric fields, fluctuating temperatures, and variations in film thickness, remains a significant challenge. Employing phase-field simulations, this study explores the evolution of polar topology and the subsequent emergence of a hexagonal close-packed skyrmion lattice phase transition, visualized in a temperature-electric field phase diagram, for ultrathin ferroelectric PbTiO3 films. An external, out-of-plane electric field can stabilize the hexagonal-lattice skyrmion crystal, meticulously balancing elastic, electrostatic, and gradient energies. Polar skyrmion crystal lattice constants, predictably, augment with film thickness, a trend in agreement with Kittel's law. Nanoscale ferroelectrics, with their topological polar textures and emergent properties, are the subject of our studies, which will lead to the development of novel ordered condensed matter phases.

Phase coherence in superradiant lasers, operating in a bad-cavity regime, is stored in the atomic medium's spin state, not in the internal electric field of the cavity. The lasers' ability to sustain lasing via collective effects potentially allows for considerably narrower linewidths than are attainable with conventional laser designs. Inside an optical cavity, we scrutinize the properties of superradiant lasing in an ensemble of ultracold strontium-88 (^88Sr) atoms. matrilysin nanobiosensors By extending the superradiant emission across the 75 kHz wide ^3P 1^1S 0 intercombination line to several milliseconds, we ascertain stable parameters, enabling the imitation of a continuous superradiant laser's efficacy via meticulous adjustments in repumping rates. During a 11-millisecond lasing period, we achieve a lasing linewidth of 820 Hz, which is about ten times smaller than the natural linewidth.

A detailed study of the ultrafast electronic structures of the 1T-TiSe2 charge density wave material was conducted with high-resolution time- and angle-resolved photoemission spectroscopy. After photoexcitation, quasiparticle populations prompted ultrafast electronic phase transitions in 1T-TiSe2, completing within 100 femtoseconds. This metastable metallic state, significantly divergent from the equilibrium normal phase, was observed considerably below the charge density wave transition temperature. The pump-fluence and time-sensitive experiments demonstrated that the photoinduced metastable metallic state's formation was the direct result of the halted atomic motion through coherent electron-phonon coupling. Utilizing the highest pump fluence in the study, the lifetime of this state was extended to picoseconds. By employing the time-dependent Ginzburg-Landau model, ultrafast electronic dynamics were effectively characterized. Our study demonstrates a mechanism where photo-induced, coherent atomic motion within the lattice leads to the realization of novel electronic states.

The creation of a single RbCs molecule is evident during the joining of two optical tweezers, one holding a single Rb atom and the other a single Cs atom, as demonstrated here. Both atoms are initially located in the most stable, lowest motional states of their individual optical traps. Analyzing the binding energy allows us to confirm the formation of the molecule and pinpoint its state. selleck products Through adjustments to trap confinement during the merging phase, we find that the likelihood of molecular formation can be regulated, findings consistent with coupled-channel calculation outcomes. selfish genetic element The conversion of atoms into molecules, as achieved by this method, exhibits comparable efficiency to magnetoassociation.

Extensive experimental and theoretical studies of 1/f magnetic flux noise in superconducting circuits have not provided a comprehensive microscopic description, leaving the problem unresolved for several decades. Significant progress in superconducting quantum devices for information processing has highlighted the need to control and reduce the sources of qubit decoherence, leading to a renewed drive to identify the fundamental mechanisms of noise. While a general agreement exists regarding the connection between flux noise and surface spins, the precise nature of these spins and their interaction mechanisms still elude definitive understanding, necessitating further investigation. By introducing weak in-plane magnetic fields, we study the dephasing of a capacitively shunted flux qubit, where the Zeeman splitting of surface spins is below the device temperature. This flux-noise-limited study yields previously unexplored trends that may shed light on the underlying dynamics producing the emergent 1/f noise. Significantly, the spin-echo (Ramsey) pure dephasing time shows an increase (or decrease) within magnetic fields reaching up to 100 Gauss. Further examination via direct noise spectroscopy showcases a transition from a 1/f dependence to approximately Lorentzian behavior below 10 Hz and a reduction in noise levels above 1 MHz concurrent with an increase in the magnetic field. We contend that the patterns we have seen are quantitatively in agreement with an enlargement of spin cluster sizes as the magnetic field is intensified. These findings provide a foundation for a comprehensive microscopic theory of 1/f flux noise in superconducting circuits.

Terahertz spectroscopy, time-resolved, at 300 Kelvin, showcased electron-hole plasma expansion with velocities exceeding c/50 and a duration lasting more than 10 picoseconds. Stimulated emission, triggered by the recombination of low-energy electron-hole pairs within a transport regime exceeding 30 meters, governs the reabsorption of emitted photons outside the plasma's volume. In a regime characterized by low temperatures, a speed of c/10 was noted when the spectral profile of the excitation pulse corresponded to the emission spectrum of photons, leading to a substantial coherent light-matter interaction and the propagation of optical solitons.

Non-Hermitian system studies often implement various strategies, which typically involve modifying existing Hermitian Hamiltonians by introducing non-Hermitian terms. Crafting non-Hermitian many-body models exhibiting features not encountered in analogous Hermitian systems can prove to be a significant hurdle. We propose, in this letter, a novel procedure for constructing non-Hermitian many-body systems, which expands upon the parent Hamiltonian method's applicability to non-Hermitian cases. Matrix product states, specified as the left and right ground states, enable the construction of a local Hamiltonian. From the asymmetric Affleck-Kennedy-Lieb-Tasaki state, we design a non-Hermitian spin-1 model that retains both chiral order and symmetry-protected topological order. Through a systematic approach to constructing and studying non-Hermitian many-body systems, our work unveils a new paradigm, providing guiding principles for exploring novel properties and phenomena in non-Hermitian physics.