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.

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.

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.

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.

The treatment of drug abuse: evolution of a perspective.

Current approaches to the treatment of drug addiction are based on an earlier approach derived from a traditional psychoanalytic framework. The author describes how this framework has been modified by three broad areas of understanding, i.e., issues related to addicts, to the methods of psychoanalysis, and to the earlier incomplete understanding about drugs. The comprehensive, multimodality treatment approach used today draws on psychoanalysis's contribution of a rational framework for the understanding of personal behavior in all forms of treatment and the need for a relationship as the core of all treatment, regardless of the modality.

Planum temporale asymmetry reversal in schizophrenia: replication and relationship to gray matter abnormalities.

OBJECTIVE: The planum temporale, the posterior superior surface of the superior temporal gyrus, is a highly lateralized brain structure involved with language. In schizophrenic patients the authors previously found consistent reversal of the normal left-larger-than-right asymmetry of planum temporale surface area. The original subjects plus new patients and comparison subjects participated in this effort to replicate and extend the prior study. METHOD: High-resolution magnetic resonance imaging of 28 schizophrenic patients and 32 group-matched normal subjects was performed. The authors measured planum temporale surface area, gray matter volume underlying the planum temporale, and gray matter thickness. Asymmetry indices for areas and volumes were calculated. RESULTS: Overall gray matter and total brain volume were not significantly smaller in the patients than in the comparison subjects. As previously reported, there was striking reversal of the normal asymmetry for planum temporale surface area in the male and female schizophrenic subjects. Bilaterally, gray matter volume beneath the planum temporale was smaller in the schizophrenic patients, and the gray matter thickness of the right planum temporale was only 50% of the comparison value. Volume of planum temporale gray matter did not show significant asymmetry in either group. CONCLUSIONS: This study extends the finding of reversed planum temporale surface area asymmetry in schizophrenic patients and clarifies its relationship to underlying gray matter volume. Although right planum temporale surface area is larger than normal in schizophrenia, gray matter volume is less than the comparison value; thus, gray matter thickness is substantially less than normal.

Asymmetry of the planum temporale: methodological considerations and clinical associations.

Asymmetry of the planum temporale, a region on the posterosuperior surface of the temporal lobe involved in the production and comprehension of language, is a notable feature of the normal human brain. Several attempts have been made to measure it using both post-mortem and magnetic resonance imaging (MRI) methods, but previous approaches made inadequate allowance for the convoluted nature of the structure. The current study used rigorous criteria to define the planum and examined three separate approaches for its measurement on MRI scans. A method involving triangulation of the surface consistently gave larger values for the surface area of the planum, suggesting that this method takes account of the convoluted nature of the structure.

Biochemical and molecular analysis of the mammalian cytoplasmic dynein intermediate chain.

Cytoplasmic dynein is a multisubunit protein complex responsible for the intracellular movement of membranous organelles and other cargo along microtubules. The heavy chains contain the motor domains, while the intermediate chain and other subunits are important for binding to cargo. There are at least five different intermediate chain polypeptides, the products of alternative splicing of two genes. The cytoplasmic dynein intermediate chains are also phosphorylated. The expression of the different intermediate chain mRNAs is characterized by reverse transcription-polymerase chain reactions using oligonucleotide primers appropriate for the alternative splicing sites. The presence of the different intermediate chain polypeptide isoforms is determined by two-dimensional gel analysis of cytoplasmic dynein samples. The phosphorylation state of the polypeptides is determined by treatment of immunoprecipitated cytoplasmic dynein with protein phosphatase and analysis of changes in polypeptide spot distribution after two-dimensional gel electrophoresis.

Expression of MsLEC1- and MsLEC2-antisense genes in alfalfa plant lines causes severe embryogenic, developmental and reproductive abnormalities.

Although it has been proposed that plant lectins play a number of roles, the function of these proteins in normal plant growth and development has been unclear. To analyze the functions of putative alfalfa lectin genes, lines of transgenic alfalfa plants expressing approximately half of the open reading frame of MsLEC1 or MsLEC2, in the antisense or sense orientation, were established and analyzed. The antisense plants displayed severe abnormalities in embryogenesis, and both vegetative and reproductive development were perturbed. Some differences were observed between MsLEC1- and MsLEC2-antisense plants, and abnormalities were especially severe during the early stages of development in both the primary and secondary transgenic generations. In contrast, vector-control and sense-transgene plants exhibited normal growth and development. MsLEC1 and MsLEC2 mRNA accumulation levels were reduced in cognate antisense plants, especially during the later stages of embryogenesis, but also tended to be low in MsLEC1 sense-transgene plants. However, correlated with the phenotypic abnormalities observed in the MsLEC1-antisense plants was the specific reduction in the accumulation of a candidate MsLEC1 protein. Our results suggest that the MsLEC1 and MsLEC2 gene products, in addition to being important for embryogenesis, are required throughout alfalfa development.

Nosocomial postoperative tetanus infection.

In light of the fact that tetanus spores are present throughout the environment, this article presents a case of nosocomial postoperative tetanus. A review of the immunization schedule is included to familiarize the surgeon with the active and passive methods of immunization. The authors recognize that tetanus infections are uncommon in our society, but all doctors should become aware of the appropriate treatment program as presented in this article.

Malignant papillary lesions of the endometrium.

In a review of 440 patients treated for endometrial adenocarcinoma at this center since 1974, 21 patients with tumors of papillary histology were identified. Eleven (2.5%) lesions contained histologic changes characteristic of uterine papillary serous carcinoma: complex papillary architecture, high nuclear/cytoplasmic ratio, and irregular epithelial tufting. Ten lesions (2.3%) containing areas of papillary morphology but lacking the criteria for the diagnosis of papillary serous tumors were termed papillary endometrioid adenocarcinoma. Patient age, stage, and the presence of obesity, hypertension, and diabetes were similar in both groups and reflected those characteristics well established for endometrial adenocarcinoma in general. Fewer papillary serous tumors (16.7%) and papillary endometrioid tumors (33.3%) contained progesterone receptors than did other adenocarcinomas (52.3%). In clinical stage I, surgical findings indicating a more advanced stage were present in 40% of patients with papillary serous tumors compared to 10% in papillary endometrioid tumors and 12.5% in nonpapillary adenocarcinomas (P = 0.03, Fisher's exact test). Recurrences were observed in 50% of patients with papillary serous lesions compared to 42.9% in papillary endometrioid lesions and 24.3% in other adenocarcinomas. Survival for clinical stage I papillary serous tumors was worse than that for nonpapillary grade 3 controls (P = 0.042) and survival for papillary endometrioid lesions was not different from that of the same controls. These findings support those of J. L. Chen, D. C. Trost, and E. J. Wilkinson (Int. J. Gynecol. Pathol. 4, 279-288 (1985)) that papillary serous and papillary endometrioid adenocarcinomas represent two distinct subtypes of papillary endometrial neoplasia.

Recombinant tobacco mosaic virus movement protein is an RNA-binding, alpha-helical membrane protein.

The 30-kDa movement protein (MP) is essential for cell-cell spread of tobacco mosaic virus in planta. To explore the structural properties of MP, the full-length recombinant MP gene was expressed in Escherichia coli, and one-step purification from solubilized inclusion bodies was accomplished by using anion exchange chromatography. Soluble MP was maintained at >4 mg/ml without aggregation and displayed approximately 70% alpha-helical conformation in the presence of urea and SDS. A trypsin-resistant core domain of the MP had tightly folded tertiary structure, whereas 18 aa at the C terminus of the monomer were rapidly removed by trypsin. Two hydrophobic regions within the core were highly resistant to proteolysis. Based on results of CD spectroscopy, trypsin treatment, and MS, we propose a topological model in which MP has two putative alpha-helical transmembrane domains and a protease-sensitive carboxyl terminus.