Our investigation focuses on the prospects of leveraging linear cross-entropy to experimentally observe measurement-induced phase transitions, without demanding any post-selection on quantum trajectories. Given two random circuits, identical in their bulk characteristics but distinct in their initial states, the linear cross-entropy value of their bulk measurement outcome distributions functions as an order parameter, facilitating the distinction between volume-law and area-law phases. Within the volume law phase (and under the constraints of the thermodynamic limit), the bulk measurements are unable to distinguish the two distinct initial states, therefore =1. Within the parameters of the area law phase, the value never exceeds 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. Furthermore, we observe that a weak depolarizing noise retains the signature of measurement-induced phase transitions, even within intermediate system sizes. Within our protocol, the selection of initial states affords the classical side efficient simulation, while quantum simulation remains classically intractable.
An associative polymer's many stickers can create reversible connections with each other. 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. Herein, we describe the design and synthesis of new unentangled associative polymer classes, distinguished by remarkably high sticker fractions, up to eight per Kuhn segment, that support strong pairwise hydrogen bonding interactions of 20k BT or greater, without exhibiting any microphase separation. Our experimental results showcase that reversible bonds significantly hinder the motion of polymers, with little influence on the pattern 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. Within the NuMI neutrino beam's target and absorber, heavy axions decay to dimuon pairs. The unique capabilities of ArgoNeuT and the MINOS near detector allow for their identification. Our research focuses on this observation. This decay channel's genesis can be traced back to a comprehensive suite of heavy QCD axion models, employing axion masses exceeding the dimuon threshold to address the strong CP and axion quality problems. Constraints on heavy axions at a 95% confidence level are obtained within the previously unexamined mass interval 0.2-0.9 GeV, for axion decay constants near the tens of TeV scale.
Polar skyrmions, swirling polarization textures possessing particle-like properties and topological stability, are promising candidates for next-generation nanoscale logic and memory devices. However, the process of forming ordered polar skyrmion lattice configurations, and the way these structures behave when subjected to electric fields, temperature changes, and modifications to the film thickness, is still unknown. Phase-field simulations are used to explore the evolution of polar topology and the emergence of a hexagonal close-packed skyrmion lattice phase transition in ultrathin PbTiO3 ferroelectric films, as graphically presented in a temperature-electric field phase diagram. To stabilize the hexagonal-lattice skyrmion crystal, an external, out-of-plane electric field is necessary, precisely managing the subtle interplay between elastic, electrostatic, and gradient energies. The lattice constants of the polar skyrmion crystals, correspondingly, increase along with the film thickness, as anticipated by Kittel's law. Our research into topological polar textures and their related emergent properties in nanoscale ferroelectrics, contributes to the creation of novel ordered condensed matter phases.
Superradiant lasers in the bad-cavity regime exhibit phase coherence stored in the spin state of the atomic medium, instead of the intracavity electric field. By harnessing collective effects, these lasers maintain lasing and could potentially achieve linewidths that are considerably narrower than typical lasers. We analyze the properties of superradiant lasing exhibited by an ultracold strontium-88 (^88Sr) atomic ensemble within an optical cavity. Afatinib manufacturer We observe sustained superradiant emission over the 75 kHz wide ^3P 1^1S 0 intercombination line, extending its duration to several milliseconds. This consistent performance permits the emulation of a continuous superradiant laser through fine-tuned repumping rates. For a 11-millisecond lasing period, a remarkably narrow lasing linewidth of 820 Hz is attained, representing a reduction almost ten times smaller than the natural linewidth.
Employing high-resolution time- and angle-resolved photoemission spectroscopy, researchers investigated the ultrafast electronic structures inherent in the charge density wave material 1T-TiSe2. Quasiparticle populations in 1T-TiSe2 were found to drive ultrafast electronic phase transitions, completing within 100 femtoseconds post-photoexcitation. A metastable metallic state, markedly distinct from the equilibrium normal phase, was observed substantially below the charge density wave transition temperature. Atomic motion halt, due to coherent electron-phonon coupling, caused by time- and pump-fluence-sensitive experiments, created the photoinduced metastable metallic state. The highest pump fluence used in this study extended the lifetime of this state to picoseconds. By employing the time-dependent Ginzburg-Landau model, ultrafast electronic dynamics were effectively characterized. The photo-induced, coherent movement of atoms in the crystal lattice is the mechanism our work reveals for achieving novel electronic states.
We showcase the genesis of a single RbCs molecule arising from the fusion of two optical tweezers; one holding a single Rb atom, the other a solitary Cs atom. At the initial time, the primary state of motion for both atoms is the ground state within their respective optical tweezers. By assessing the binding energy, we confirm the molecule's formation and characterize its state. Next Gen Sequencing The merging process's influence on molecule formation probability is demonstrably controllable via trap confinement adjustments, which resonates with results from coupled-channel computations. Leber’s Hereditary Optic Neuropathy This technique's performance in converting atoms into molecules is equivalent to the efficiency of magnetoassociation.
Numerous experimental and theoretical investigations into 1/f magnetic flux noise within superconducting circuits have not yielded a conclusive microscopic description, leaving the question open for several decades. Recent advancements in superconducting quantum information technology have underscored the need to minimize qubit decoherence, thereby reinvigorating the investigation into the core noise mechanisms at play. A growing consensus associates flux noise with surface spins, but the particular types of these spins and the precise mechanisms governing their interaction are still unclear, thus driving the need for further exploration. A capacitively shunted flux qubit, characterized by a Zeeman splitting of surface spins that is less than the device temperature, experiences weak in-plane magnetic fields. The flux-noise-limited qubit dephasing is then examined, uncovering novel trends which may offer insights into the dynamics driving the emergence of 1/f noise. A noteworthy observation is the improvement (or reduction) of the spin-echo (Ramsey) pure dephasing time in magnetic fields up to 100 Gauss. Our further direct noise spectroscopy findings reveal a transition from a 1/f dependence to an approximate Lorentzian frequency dependency below 10 Hz, and a reduction in noise observed above 1 MHz while increasing the magnetic field. We posit that the observed trends align with an increase in spin cluster size as the magnetic field strengthens. To create a complete microscopic theory of 1/f flux noise in superconducting circuits, these results are essential.
At 300 Kelvin, time-resolved terahertz spectroscopy demonstrated electron-hole plasma expansion, with velocities surpassing c/50 and durations exceeding 10 picoseconds. Reabsorption of emitted photons outside the plasma volume, which is a consequence of stimulated emission from low-energy electron-hole pair recombination, is the governing principle of this regime, characterized by carrier transport exceeding 30 meters. Measurements at low temperatures revealed a speed of c/10 within the spectral overlap of excitation pulses and emitted photons, fostering strong coherent light-matter interaction and the propagation of optical solitons.
Non-Hermitian systems research frequently incorporates strategies that add non-Hermitian elements to pre-existing Hermitian Hamiltonians. Crafting non-Hermitian many-body models exhibiting features not encountered in analogous Hermitian systems can prove to be a significant hurdle. This letter introduces a new technique for the construction of non-Hermitian many-body systems, by adapting the parent Hamiltonian method to the realm of non-Hermitian physics. From the provided matrix product states, designated as the left and right ground states, a local Hamiltonian can be formulated. The construction of a non-Hermitian spin-1 model from the asymmetric Affleck-Kennedy-Lieb-Tasaki state is demonstrated, ensuring the persistence of both chiral order and symmetry-protected topological order. The systematic construction and study of non-Hermitian many-body systems, as articulated by our approach, establishes a new paradigm, providing a basis for investigating new properties and phenomena in non-Hermitian physics.