Formation of robust bound states of interacting microwave photons.

Systems of correlated particles appear in many fields of modern science and represent some of the most intractable computational problems in nature. The computational challenge in these systems arises when interactions become comparable to other energy scales, which makes the state of each particle depend on all other particles1. The lack of general solutions for the three-body problem and acceptable theory for strongly correlated electrons shows that our understanding of correlated systems fades when the particle number or the interaction strength increases. One of the hallmarks of interacting systems is the formation of multiparticle bound states2-9. Here we develop a high-fidelity parameterizable fSim gate and implement the periodic quantum circuit of the spin-½ XXZ model in a ring of 24 superconducting qubits. We study the propagation of these excitations and observe their bound nature for up to five photons. We devise a phase-sensitive method for constructing the few-body spectrum of the bound states and extract their pseudo-charge by introducing a synthetic flux. By introducing interactions between the ring and additional qubits, we observe an unexpected resilience of the bound states to integrability breaking. This finding goes against the idea that bound states in non-integrable systems are unstable when their energies overlap with the continuum spectrum. Our work provides experimental evidence for bound states of interacting photons and discovers their stability beyond the integrability limit.

Accurately computing the electronic properties of a quantum ring.

A promising approach to study condensed-matter systems is to simulate them on an engineered quantum platform1-4. However, the accuracy needed to outperform classical methods has not been achieved so far. Here, using 18 superconducting qubits, we provide an experimental blueprint for an accurate condensed-matter simulator and demonstrate how to investigate fundamental electronic properties. We benchmark the underlying method by reconstructing the single-particle band structure of a one-dimensional wire. We demonstrate nearly complete mitigation of decoherence and readout errors, and measure the energy eigenvalues of this wire with an error of approximately 0.01 rad, whereas typical energy scales are of the order of 1 rad. Insight into the fidelity of this algorithm is gained by highlighting the robust properties of a Fourier transform, including the ability to resolve eigenenergies with a statistical uncertainty of 10-4 rad. We also synthesize magnetic flux and disordered local potentials, which are two key tenets of a condensed-matter system. When sweeping the magnetic flux we observe avoided level crossings in the spectrum, providing a detailed fingerprint of the spatial distribution of local disorder. By combining these methods we reconstruct electronic properties of the eigenstates, observing persistent currents and a strong suppression of conductance with added disorder. Our work describes an accurate method for quantum simulation5,6 and paves the way to study new quantum materials with superconducting qubits.

Adaptation of the polarimetric multi-spectral Aerosol Limb Imager for high altitude aircraft and satellite observations.

An elegant breadboard prototype of the Aerosol Limb Imager (ALI) has been developed to meet key performance parameters that will meet requirements for the retrieval of aerosol from the upper troposphere and stratosphere from limb scattered sunlight radiance measurements. Similar in concept to previous high altitude balloon-based generations, this instrument pairs a liquid crystal polarization rotator with an acousto-optic tunable filter to capture polarimetric multi-spectral images of the atmospheric limb. This design improves the vertical resolution, signal-to-noise ratio, and athermalization, all of which will facilitate observation from a moving high altitude aircraft platform, which provides a platform analogous to the spatially varying measurements that would be made from a satellite. Finally, a preliminary design is presented for a satellite-based generation of ALI.

Measurement of water vapor using an imaging field-widened spatial heterodyne spectrometer.

Spatial heterodyne spectroscopy (SHS) has been successfully applied to measure variations in water vapor pressure in the lab. An imaging system is combined with a monolithic field-widened SHS to observe a white-light source through a 1 m length water vapor cell that is designed to produce predictable variations in the water vapor pressure. The performance of the spectrometer design is examined by comparing spectra simulated using a radiative transfer model to observed spectra at several cell pressures. The intended application of the instrument to vertically resolve the water vapor profile in the upper troposphere and lower stratosphere using limb-scattered radiation in a vibrational band of water (1363-1366 nm) is also introduced.

Stable quantum-correlated many-body states through engineered dissipation.

Engineered dissipative reservoirs have the potential to steer many-body quantum systems toward correlated steady states useful for quantum simulation of high-temperature superconductivity or quantum magnetism. Using up to 49 superconducting qubits, we prepared low-energy states of the transverse-field Ising model through coupling to dissipative auxiliary qubits. In one dimension, we observed long-range quantum correlations and a ground-state fidelity of 0.86 for 18 qubits at the critical point. In two dimensions, we found mutual information that extends beyond nearest neighbors. Lastly, by coupling the system to auxiliaries emulating reservoirs with different chemical potentials, we explored transport in the quantum Heisenberg model. Our results establish engineered dissipation as a scalable alternative to unitary evolution for preparing entangled many-body states on noisy quantum processors.

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]. The first two moments of [Formula: see text] show superdiffusive behavior, a hallmark of KPZ universality. However, the third and fourth moments ruled out the KPZ conjecture and allow for evaluating other theories. Our results highlight the importance of studying higher moments in determining dynamic universality classes and provide insights into universal behavior in quantum systems.

Noise-resilient edge modes on a chain of superconducting qubits.

Inherent symmetry of a quantum system may protect its otherwise fragile states. Leveraging such protection requires testing its robustness against uncontrolled environmental interactions. Using 47 superconducting qubits, we implement the one-dimensional kicked Ising model, which exhibits nonlocal Majorana edge modes (MEMs) with [Formula: see text] parity symmetry. We find that any multiqubit Pauli operator overlapping with the MEMs exhibits a uniform late-time decay rate comparable to single-qubit relaxation rates, irrespective of its size or composition. This characteristic allows us to accurately reconstruct the exponentially localized spatial profiles of the MEMs. Furthermore, the MEMs are found to be resilient against certain symmetry-breaking noise owing to a prethermalization mechanism. Our work elucidates the complex interplay between noise and symmetry-protected edge modes in a solid-state environment.

A multi-spectral polarimetric imager for atmospheric profiling of aerosol and thin cloud: Prototype design and sub-orbital performance.

We report on the development of a novel multi-spectral polarimetric imager for atmospheric remote sensing of aerosol and cloud properties. The instrument concept, called the Aerosol Limb Imager (ALI), is ultimately intended for satellite measurements from a low Earth orbit. It utilizes a coupling of a dual transducer acousto-optic tunable filter and a liquid crystal rotator to provide dual linear polarization observations over a wide spectral range covering 600 nm-1500 nm. In the limb, or side-viewing, geometry, these measurements provide the capability to resolve vertical and horizontal distributions of aerosol and cloud properties such as extinction coefficient, optical depth, and particle distribution parameters. Here, we present the design and performance of an ALI prototype. Lab characterization of the instrument is used to develop a mathematical instrument model to predict signal levels under various atmospheric conditions. Results from a sub-orbital flight of the ALI prototype on a stabilized high-altitude stratospheric balloon gondola are presented that show the first known polarimetric, multi-spectral images of the limb radiance. The signal levels obtained agree reasonably well with those predicted by the instrument model using radiative transfer calculations for typical atmospheric conditions.

[Nutritional recommendations and risk of death from all causes]. / Recommandations sur la nutrition et risque de décès de toutes causes.

This study evaluated the relationship between meeting the Nutrition Recommendations and mortality from all causes in a cohort of 1,623 men from the Quebec City area followed from 1985 to 1991. The usual dietary intake was assessed by a self-administered semi-quantitative food frequency questionnaire. Most participants did not meet the Nutrition Recommendations. During the follow-up 69 men died. The mortality was significantly lower among those who did not meet the recommendations for total fat (RR = 0.45, CI: 0.25-0.81) or for carbohydrates (RR = 0.49, CI: 0.26-0.92). This unexpected result could be attributable to an excessive alcohol intake or to dietary changes in the direction of the Nutrition Recommendations, made prior to the dietary assessment often because of illness. It would be interesting to continue the follow-up of this cohort to evaluate the long-term effect of a diet meeting the Nutrition Recommendations on mortality from all causes.

Antagonism of the effects of adenosine and hypoxia on atrioventricular conduction time by two novel alkylxanthines: correlation with binding to adenosine A1 receptors.

Adenosine has been shown to have a negative dromotropic effect and has been implicated in mediating atrioventricular conduction disturbances induced by hypoxia. This study was designed to determine the ability of various alkylxanthines including two novel derivatives, i.e., BW A533U and BW A1433U, to 1) attenuate adenosine- and hypoxia-induced atrial to His bundle (AH) interval prolongation, 2) compete for binding of 125I-aminobenzyladenosine to ventricular membranes and 3) inhibit myocardial phosphodiesterase. In normoxic isolated perfused hearts (n = 20) instrumented for measurement of atrioventricular conduction time and left ventricular pressure, BW A1433U (0.1 microM) or BW A533U (5 microM) attenuated AH interval prolongation induced by adenosine (5 microM) by 90%, but neither xanthine derivative attenuated the AH interval prolongation induced by acetylcholine (0.11 microM), digoxin (0.91 microM) or D600 (1.3 microM). In four additional hearts, BW A1433U at concentrations of up to 10 microM had no effect on left ventricular pressure or AH interval. BW A1433 or BW A533U (50 microM) inhibited myocardial cyclic AMP phosphodiesterase by only 11.5 +/- 1.6 and 26.6 +/- 2.6%, respectively. Schild analysis of adenosine concentration-response curves obtained in the absence and presence of BW A533U and BW A1433U (n = 14) yielded pA2 values of (mean +/- S.E.M.) 6.32 +/- 0.10 and 7.70 +/- 0.08, respectively. pKd values for BW A533U and BW A1433U binding to adenosine receptors on ventricular membranes were 6.36 and 6.94, respectively. In a separate series of 19 hearts, BW A533U and BW A1433U were shown to attenuate hypoxia-induced AH interval prolongation.(ABSTRACT TRUNCATED AT 250 WORDS)