Quantum Turnstiles for Robust Measurement of Full Counting Statistics.

We present a scalable protocol for measuring full counting statistics (FCS) in experiments or tensor-network simulations. In this method, an ancilla in the middle of the system acts as a turnstile, with its phase keeping track of the time-integrated particle flux. Unlike quantum gas microscopy, the turnstile protocol faithfully captures FCS starting from number-indefinite initial states or in the presence of noisy dynamics.

Shape-persistent ladder molecules exhibit nanogap-independent conductance in single-molecule junctions.

Molecular electronic devices require precise control over the flow of current in single molecules. However, the electron transport properties of single molecules critically depend on dynamic molecular conformations in nanoscale junctions. Here we report a unique strategy for controlling molecular conductance using shape-persistent molecules.

Origin of Secondary Structure Transitions and Peptide Self-Assembly Propensity in Trifluoroethanol-Water Mixtures.

Membrane-peptide interactions are key to the formation of helical intermediates in the early stages of amyloidogenesis. Aqueous solutions of 2,2,2-trifluoroethanol (TFE) provide a membrane-mimetic environment capable of promoting and stabilizing local peptide interactions. Uperin 3.

Secondary structure determines electron transport in peptides.

Proteins play a key role in biological electron transport, but the structure-function relationships governing the electronic properties of peptides are not fully understood. Despite recent progress, understanding the link between peptide conformational flexibility, hierarchical structures, and electron transport pathways has been challenging. Here, we use single-molecule experiments, molecular dynamics (MD) simulations, nonequilibrium Green's function-density functional theory (NEGF-DFT), and unsupervised machine learning to understand the role of secondary structure on electron transport in peptides.

Dynamics of magnetization at infinite temperature in a Heisenberg spin chain.

Understanding universal aspects of quantum dynamics is an unresolved problem in statistical mechanics. In particular, the spin dynamics of the one-dimensional Heisenberg model were conjectured as to belong to the Kardar-Parisi-Zhang (KPZ) universality class based on the scaling of the infinite-temperature spin-spin correlation function. In a chain of 46 superconducting qubits, we studied the probability distribution of the magnetization transferred across the chain's center, [Formula: see text].

Emergent Glassy Behavior in a Kagome Rydberg Atom Array.

We present large-scale quantum Monte Carlo simulation results on a realistic Hamiltonian of kagome-lattice Rydberg atom arrays. Although the system has no intrinsic disorder, intriguingly, our analyses of static and dynamic properties on large system sizes reveal emergent glassy behavior in a region of parameter space located between two valence bond solid phases. The extent of this glassy region is demarcated using the Edwards-Anderson order parameter, and its phase transitions to the two proximate valence bond solids-as well as the crossover towards a trivial paramagnetic phase-are identified.

Emergent Z_{2} Gauge Theories and Topological Excitations in Rydberg Atom Arrays.

Strongly interacting arrays of Rydberg atoms provide versatile platforms for exploring exotic many-body phases and dynamics of correlated quantum systems. Motivated by recent experimental advances, we show that the combination of Rydberg interactions and appropriate lattice geometries naturally leads to emergent Z_{2} gauge theories endowed with matter fields. Based on this mapping, we describe how Rydberg platforms could realize two distinct classes of topological Z_{2} quantum spin liquids, which differ in their patterns of translational symmetry fractionalization.

Triangular lattice quantum dimer model with variable dimer density.

Quantum dimer models are known to host topological quantum spin liquid phases, and it has recently become possible to simulate such models with Rydberg atoms trapped in arrays of optical tweezers. Here, we present large-scale quantum Monte Carlo simulation results on an extension of the triangular lattice quantum dimer model with terms in the Hamiltonian annihilating and creating single dimers. We find distinct odd and even [Formula: see text] spin liquids, along with several phases with no topological order: a staggered crystal, a nematic phase, and a trivial symmetric phase with no obvious broken symmetry.

Transition Metal Phthalocyanines as Redox Mediators in Li-O Batteries: A Combined Experimental and Theoretical Study of the Influence of 3d Electrons in Redox Mediation.

Redox mediation is an innovative strategy for ensuring efficient energy harvesting from metal-oxygen systems. This work presents a systematic exploratory analysis of first-row transition-metal phthalocyanines as solution-state redox mediators for lithium-oxygen batteries. Our findings, based on experiment and theory, convincingly demonstrate that d (Mn), d (Co), and d (Ni) configurations function better compared to d (Fe) and d (Cu) in redox mediation of the discharge step.

Quantum optimization of maximum independent set using Rydberg atom arrays.

Realizing quantum speedup for practically relevant, computationally hard problems is a central challenge in quantum information science. Using Rydberg atom arrays with up to 289 qubits in two spatial dimensions, we experimentally investigate quantum algorithms for solving the maximum independent set problem. We use a hardware-efficient encoding associated with Rydberg blockade, realize closed-loop optimization to test several variational algorithms, and subsequently apply them to systematically explore a class of graphs with programmable connectivity.

Probing topological spin liquids on a programmable quantum simulator.

Quantum spin liquids, exotic phases of matter with topological order, have been a major focus in physics for the past several decades. Such phases feature long-range quantum entanglement that can potentially be exploited to realize robust quantum computation. We used a 219-atom programmable quantum simulator to probe quantum spin liquid states.

Quantum phases of matter on a 256-atom programmable quantum simulator.

Motivated by far-reaching applications ranging from quantum simulations of complex processes in physics and chemistry to quantum information processing, a broad effort is currently underway to build large-scale programmable quantum systems. Such systems provide insights into strongly correlated quantum matter, while at the same time enabling new methods for computation and metrology. Here we demonstrate a programmable quantum simulator based on deterministically prepared two-dimensional arrays of neutral atoms, featuring strong interactions controlled by coherent atomic excitation into Rydberg states.

Structure-Redox Response Correlation in a Few Select Heme Systems Using X-ray Absorption Spectroelectrochemistry.

Heme based biomolecules control some of the most crucial life processes, such as oxygen and electron transport during respiration and energy metabolism, respectively. The active site of the heme, viz., the metal center, plays a key role and attributes functionality to these biomolecules.

Quantum phases of Rydberg atoms on a kagome lattice.

We analyze the zero-temperature phases of an array of neutral atoms on the kagome lattice, interacting via laser excitation to atomic Rydberg states. Density-matrix renormalization group calculations reveal the presence of a wide variety of complex solid phases with broken lattice symmetries. In addition, we identify a regime with dense Rydberg excitations that has a large entanglement entropy and no local order parameter associated with lattice symmetries.

Hemoglobin Dynamics in Solution vis-à-vis Under Confinement: An Electrochemical Perspective.

Confining heme protein often leads to beneficial functionalities such as an enhanced electrochemical response from the heme center. This can be harnessed to design effective biosensors for medical diagnostics. Proteins under confinement, to be precise, have more ordered and monodisperse structure compared to the protein in bulk solution.

Complex Density Wave Orders and Quantum Phase Transitions in a Model of Square-Lattice Rydberg Atom Arrays.

We describe the zero-temperature phase diagram of a model of a two-dimensional square-lattice array of neutral atoms, excited into Rydberg states and interacting via strong van der Waals interactions. Using the density-matrix renormalization group algorithm, we map out the phase diagram and obtain a rich variety of phases featuring complex density wave orderings, upon varying lattice spacing and laser detuning. While some of these phases result from the classical optimization of the van der Waals energy, we also find intrinsically quantum-ordered phases stabilized by quantum fluctuations.

Studying Hemoglobin and a Bare Metal-Porphyrin Complex Immobilized on Functionalized Silicon Surfaces Using Synchrotron X-ray Reflectivity.

We evaluate here, using synchrotron X-ray reflectivity, hemoglobin adsorption characteristics on silicon substrates with varying chemical functionalities. Hemoglobin at isoelectronic point and at negative charge is immobilized on functionalized hydrophilic (hydroxyl, carboxylic, amine) and hydrophobic (alkylated) silicon surfaces for the study. As a control, the bare cofactor hemin (containing only the metal and porphyrin with no amino acid residues) is also studied under similar conditions.

Quantum Kibble-Zurek mechanism and critical dynamics on a programmable Rydberg simulator.

Quantum phase transitions (QPTs) involve transformations between different states of matter that are driven by quantum fluctuations. These fluctuations play a dominant part in the quantum critical region surrounding the transition point, where the dynamics is governed by the universal properties associated with the QPT. Although time-dependent phenomena associated with classical, thermally driven phase transitions have been extensively studied in systems ranging from the early Universe to Bose-Einstein condensates, understanding critical real-time dynamics in isolated, non-equilibrium quantum systems remains a challenge.

Quantum field theory for the chiral clock transition in one spatial dimension.

We describe the quantum phase transition in the -state chiral clock model in spatial dimension . With couplings chosen to preserve time-reversal and spatial inversion symmetries, such a model is in the universality class of recent experimental studies of the ordering of pumped Rydberg states in a one-dimensional chain of trapped ultracold alkali atoms. For such couplings and , the clock model is expected to have a direct phase transition from a gapped phase with a broken global symmetry, to a gapped phase with the symmetry restored.

Self-Assembled Pd Molecular Spheroids and Their Proton Conduction Property.

A series of molecular spheroids (SP1-SP4) was synthesized using pseudolinear bisimidazole and bisbenzimidazole donors in combination with Pd(NO) acceptor via coordination-driven self-assembly. They were characterized by NMR and mass spectrometry, and the solid-state structures of SP1 and SP3 were confirmed by X-ray diffraction. Crystal packing revealed the presence of molecular channels with water molecules in the channels as proton source.

Using porphyrin-amino acid pairs to model the electrochemistry of heme proteins: experimental and theoretical investigations.

Quasi reversibility in electrochemical cycling between different oxidation states of iron is an often seen characteristic of iron containing heme proteins that bind dioxygen. Surprisingly, the system becomes fully reversible in the bare iron-porphyrin complex: hemin. This leads to the speculation that the polypeptide bulk (globin) around the iron-porphyrin active site in these heme proteins is probably responsible for the electrochemical quasi reversibility.

Unique Features of Metformin: A Combined Experimental, Theoretical, and Simulation Study of Its Structure, Dynamics, and Interaction Energetics with DNA Grooves.

There are certain small molecules that exhibit extraordinarily diverse biological activities. Metformin is one of them. It is widely used as an antidiabetic drug for type-two diabetes.

Determination of Redox Sensitivity in Structurally Similar Biological Redox Sensors.

Redox stimuli govern a variety of biological processes. The relative sensitivity of redox sensors plays an important role in providing a calibrated response to environmental stimuli and cellular homeostasis. This cellular machinery plays a crucial role in the human pathogen Mycobacterium tuberculosis as it encounters diverse microenvironments in the host.