RESUMEN
Social interactions are a crucial aspect of human behaviour. Numerous neurophysiological studies have focused on socio-cognitive processes associated with the so-called theory of mind-the ability to attribute mental states to oneself and others. Theory of mind is closely related to social intelligence defined as a set of abilities that facilitate effective social interactions. Social intelligence encompasses multiple theory of mind components and can be measured by the Four Factor Test of Social Intelligence (the Guilford-Sullivan test). However, it is unclear whether the differences in social intelligence are reflected in structural brain differences. During the experiment, 48 healthy right-handed individuals completed the Guilford-Sullivan test. T1-weighted structural MRI images were obtained for all participants. Voxel-based morphometry analysis was performed to reveal grey matter volume differences between the two groups (24 subjects in each)-with high social intelligence scores and with low social intelligence scores, respectively. Participants with high social intelligence scores had larger grey matter volumes of the bilateral caudate. The obtained results suggest the caudate nucleus involvement in the neural system of socio-cognitive processes, reflected by its structural characteristics.
Asunto(s)
Cognición , Sustancia Gris , Encéfalo/diagnóstico por imagen , Inteligencia Emocional , Sustancia Gris/diagnóstico por imagen , Humanos , Imagen por Resonancia MagnéticaRESUMEN
AIMS: Oxidative stress is evident in resected epileptogenic brain tissue of patients with developmental brain malformations related to mammalian target of rapamycin activation: tuberous sclerosis complex (TSC) and focal cortical dysplasia type IIb (FCD IIb). Whether chronic activation of anti-oxidant pathways is beneficial or contributes to pathology is not clear. METHODS: We investigated oxidative stress markers, including haem oxygenase 1, ferritin and the inflammation associated microRNA-155 in surgically resected epileptogenic brain tissue of TSC (n = 10) and FCD IIb (n = 8) patients and in a TSC model (Tsc1GFAP-/- mice) using immunohistochemistry, in situ hybridization, real-time quantitative PCR and immunoblotting. Using human foetal astrocytes we performed an in vitro characterization of the anti-oxidant response to acute and chronic oxidative stress and evaluated overexpression of the disease-relevant pro-inflammatory microRNA-155. RESULTS: Resected TSC or FCD IIb tissue displayed higher expression of oxidative stress markers and microRNA-155. Tsc1GFAP-/- mice expressed more microRNA-155 and haem oxygenase 1 in the brain compared to wild-type, preceding the typical development of spontaneous seizures in these animals. In vitro, chronic microRNA-155 overexpression induced haem oxygenase 1, iron regulatory elements and increased susceptibility to oxidative stress. Overexpression of iron regulatory genes was also detected in patients with TSC, FCD IIb and Tsc1GFAP-/- mice. CONCLUSION: Our results demonstrate that early and sustained activation of anti-oxidant signalling and dysregulation of iron metabolism are a pathological hallmark of FCD IIb and TSC. Our findings suggest novel therapeutic strategies aimed at controlling the pathological link between both processes.
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Antioxidantes/metabolismo , Epilepsia/metabolismo , Hierro/metabolismo , Malformaciones del Desarrollo Cortical/complicaciones , Malformaciones del Desarrollo Cortical/metabolismo , Redes y Vías Metabólicas , Animales , Células Cultivadas , Encefalitis/genética , Encefalitis/metabolismo , Epilepsia/complicaciones , Epilepsia/genética , Femenino , Ferritinas/metabolismo , Proteína Ácida Fibrilar de la Glía/genética , Hemo-Oxigenasa 1/metabolismo , Humanos , Masculino , Malformaciones del Desarrollo Cortical/genética , Malformaciones del Desarrollo Cortical de Grupo I/genética , Malformaciones del Desarrollo Cortical de Grupo I/metabolismo , Ratones , Ratones Noqueados , MicroARNs/genética , Estrés Oxidativo , Esclerosis Tuberosa/genética , Esclerosis Tuberosa/metabolismoRESUMEN
Quantum algorithms offer a dramatic speedup for computational problems in material science and chemistry. However, any near-term realizations of these algorithms will need to be optimized to fit within the finite resources offered by existing noisy hardware. Here, taking advantage of the adjustable coupling of gmon qubits, we demonstrate a continuous two-qubit gate set that can provide a threefold reduction in circuit depth as compared to a standard decomposition. We implement two gate families: an imaginary swap-like (iSWAP-like) gate to attain an arbitrary swap angle, θ, and a controlled-phase gate that generates an arbitrary conditional phase, Ï. Using one of each of these gates, we can perform an arbitrary two-qubit gate within the excitation-preserving subspace allowing for a complete implementation of the so-called Fermionic simulation (fSim) gate set. We benchmark the fidelity of the iSWAP-like and controlled-phase gate families as well as 525 other fSim gates spread evenly across the entire fSim(θ,Ï) parameter space, achieving a purity-limited average two-qubit Pauli error of 3.8×10^{-3} per fSim gate.
RESUMEN
A quantum computer can solve hard problems, such as prime factoring, database searching and quantum simulation, at the cost of needing to protect fragile quantum states from error. Quantum error correction provides this protection by distributing a logical state among many physical quantum bits (qubits) by means of quantum entanglement. Superconductivity is a useful phenomenon in this regard, because it allows the construction of large quantum circuits and is compatible with microfabrication. For superconducting qubits, the surface code approach to quantum computing is a natural choice for error correction, because it uses only nearest-neighbour coupling and rapidly cycled entangling gates. The gate fidelity requirements are modest: the per-step fidelity threshold is only about 99 per cent. Here we demonstrate a universal set of logic gates in a superconducting multi-qubit processor, achieving an average single-qubit gate fidelity of 99.92 per cent and a two-qubit gate fidelity of up to 99.4 per cent. This places Josephson quantum computing at the fault-tolerance threshold for surface code error correction. Our quantum processor is a first step towards the surface code, using five qubits arranged in a linear array with nearest-neighbour coupling. As a further demonstration, we construct a five-qubit Greenberger-Horne-Zeilinger state using the complete circuit and full set of gates. The results demonstrate that Josephson quantum computing is a high-fidelity technology, with a clear path to scaling up to large-scale, fault-tolerant quantum circuits.
RESUMEN
The act of measurement bridges the quantum and classical worlds by projecting a superposition of possible states into a single (probabilistic) outcome. The timescale of this 'instantaneous' process can be stretched using weak measurements, such that it takes the form of a gradual random walk towards a final state. Remarkably, the interim measurement record is sufficient to continuously track and steer the quantum state using feedback. Here we implement quantum feedback control in a solid-state system, namely a superconducting quantum bit (qubit) coupled to a microwave cavity. A weak measurement of the qubit is implemented by probing the cavity with microwave photons, maintaining its average occupation at less than one photon. These photons are then directed to a high-bandwidth, quantum-noise-limited amplifier, which allows real-time monitoring of the state of the cavity (and, hence, that of the qubit) with high fidelity. We demonstrate quantum feedback control by inhibiting the decay of Rabi oscillations, allowing them to persist indefinitely. Such an ability permits the active suppression of decoherence and enables a method of quantum error correction based on weak continuous measurements. Other applications include quantum state stabilization, entanglement generation using measurement, state purification and adaptive measurements.
RESUMEN
Leakage errors occur when a quantum system leaves the two-level qubit subspace. Reducing these errors is critically important for quantum error correction to be viable. To quantify leakage errors, we use randomized benchmarking in conjunction with measurement of the leakage population. We characterize single qubit gates in a superconducting qubit, and by refining our use of derivative reduction by adiabatic gate pulse shaping along with detuning of the pulses, we obtain gate errors consistently below 10^{-3} and leakage rates at the 10^{-5} level. With the control optimized, we find that a significant portion of the remaining leakage is due to incoherent heating of the qubit.
RESUMEN
The review states and argues theoretical propositions on the pathogenetic role of pre- and perinatal hypoxic-ischemic brain damage in the formation of sustained oxygen-dependent energy deficit underlying in further ontogenesis the following neurobiological abnormalities: a) a decline in the level of health and compensatory-adaptive capacities of the organism, b) disorders of the psycho-speech development and adaptive behavior in children, c) early development of neuropsychic diseases, g) addition of other types of brain energy metabolism (including glucose metabolism) disorders in chronic polyetiologic diseases young and middle-aged individuals. We highlight and theoretically substantiate the integrated physiological parameters of the oxygen-dependent energy deficit types. We address the features of abnormalities in neuroreflectory and neurohumora regulatory mechanisms of the wakefulness level and its vegetative and hemodynamic provision in different types of energy deficit in children with DSMD, ADHD and school maladjustment. The use of the state-of-the-art neuroimaging techniques significantly increased the possibility of the disintegration of regulatory processes and cognitive functions in children with psycho-speech delays and in a wide range of chronic polyetiologic diseases.
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Sistema Nervioso Central/metabolismo , Discapacidades del Desarrollo/metabolismo , Metabolismo Energético , Consumo de Oxígeno , Trastorno por Déficit de Atención con Hiperactividad/metabolismo , Trastorno por Déficit de Atención con Hiperactividad/fisiopatología , Encéfalo/metabolismo , Encéfalo/fisiopatología , Sistema Nervioso Central/fisiopatología , Niño , Cognición/fisiología , Discapacidades del Desarrollo/fisiopatología , Glucosa/metabolismo , HumanosRESUMEN
The present paper dedicated to the research of the functional interactions between brain structures while executing deliberate deceptive actions. Based on our own and literature data, we formulated the hypothesis that the functional interaction between brain areas responsible for the executive control, localized in the prefrontal cortex (inferior frontal gyrus), and the elements of error detection brain system, underlies deception. To test this hypothesis, we applied an analysis of the psychophysiological interaction (PPI), which revealed that the false actions (in comparison with true honestones) associated with increased functional connectivity between the left caudate nucleus and the left inferior frontal gyrus. Obtained experimental data support our hypothesis that the interaction of neural brain systems, which are responsible for executive control and error detection, underpins the brain maintenance of the execution of deceptive actions.
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Núcleo Caudado/fisiología , Decepción , Corteza Prefrontal/fisiología , Percepción Visual/fisiología , Adulto , Femenino , Humanos , MasculinoRESUMEN
The creation of a quantum network requires the distribution of coherent information across macroscopic distances. We demonstrate the entanglement of two superconducting qubits, separated by more than a meter of coaxial cable, by designing a joint measurement that probabilistically projects onto an entangled state. By using a continuous measurement scheme, we are further able to observe single quantum trajectories of the joint two-qubit state, confirming the validity of the quantum Bayesian formalism for a cascaded system. Our results allow us to resolve the dynamics of continuous projection onto the entangled manifold, in quantitative agreement with theory.
RESUMEN
Two recombinant proteins with three copies of the ectodomain of the conserved influenza protein M2 (M2e) of influenza viruses were developed: A (H1N1)pdm09, A/Kurgan/05/05 (H5N1), and M2e consensus sequence of the human influenza A virus (H1N1, H2N2, H3N2) based on flagellin and core antigen of hepatitis B (HBc). The first recombinant protein comprised flagellin fused to three tandem copies of M2e, the second preparation was based on non-covalent interaction between M2e peptides and HBc. The immunogenicity of two preparations was comparatively tested. A covalent linkage of flagellin with M2e significant increased the immunogenicity of the target antigen compared with non-covalent interaction M2e and HBc. Flagellin as a protein carrier of M2e induced mainly IgG1 subclass, whereas HBc stimulated more balanced Th1/Th2 response. Our study showed a decrease in the viral titers in lung tissues of immunized mice after lethal challenge of A/PR/8/34 (H1N1). The study revealed a possibility to obtain a vaccine preparation with equal immunogenicity both against human influenza viruses and highly pathogenic avian influenza viruses.
Asunto(s)
Anticuerpos Antivirales/inmunología , Flagelina/genética , Vacunas contra la Influenza/inmunología , Gripe Humana/prevención & control , Infecciones por Orthomyxoviridae/prevención & control , Proteínas Recombinantes de Fusión/inmunología , Proteínas de la Matriz Viral/genética , Secuencia de Aminoácidos , Animales , Anticuerpos Antivirales/sangre , Protección Cruzada , Flagelina/inmunología , Expresión Génica , Humanos , Inmunoglobulina G/sangre , Inmunoglobulina G/inmunología , Subtipo H1N1 del Virus de la Influenza A/genética , Subtipo H1N1 del Virus de la Influenza A/inmunología , Subtipo H2N2 del Virus de la Influenza A/genética , Subtipo H2N2 del Virus de la Influenza A/inmunología , Subtipo H3N2 del Virus de la Influenza A/genética , Subtipo H3N2 del Virus de la Influenza A/inmunología , Subtipo H5N1 del Virus de la Influenza A/genética , Subtipo H5N1 del Virus de la Influenza A/inmunología , Vacunas contra la Influenza/administración & dosificación , Vacunas contra la Influenza/genética , Gripe Humana/inmunología , Gripe Humana/virología , Ratones , Datos de Secuencia Molecular , Infecciones por Orthomyxoviridae/inmunología , Infecciones por Orthomyxoviridae/virología , Estructura Terciaria de Proteína , Proteínas Recombinantes de Fusión/administración & dosificación , Proteínas Recombinantes de Fusión/genética , Vacunación , Vacunas Sintéticas , Carga Viral , Proteínas de la Matriz Viral/inmunologíaRESUMEN
In the present article it was shown that the functional connectivity of brain structures, revealed by factor analysis of resting PET CBF and rCMRglu data, is an adequate tool to study the default mode of the human brain. The identification of neuroanatomic systems of default mode (default mode network) during routine clinical PET investigations is important for further studying the functional organization of the normal brain and its reorganizations in pathological conditions.
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Mapeo Encefálico , Encéfalo , Red Nerviosa , Adolescente , Adulto , Encéfalo/irrigación sanguínea , Encéfalo/diagnóstico por imagen , Encéfalo/fisiología , Encéfalo/fisiopatología , Femenino , Glucosa/metabolismo , Humanos , Masculino , Persona de Mediana Edad , Red Nerviosa/fisiología , Red Nerviosa/fisiopatología , Neuroanatomía , Tomografía de Emisión de Positrones , Radiografía , Descanso/fisiologíaRESUMEN
In this paper possible mechanism of improvement of the functional state of the brain areas, maintaining movement, visual, auditory, and higher functions of the brain during correction of generalized spastic syndrome (botulinotherapy with Xeomin) in patients in a vegetative state (VS) is discussed. If to consider the vegetative state as stable pathological condition (SPC) of the brain, then from the perspective of the theory of structural and functional organization of the brain with systems with rigid and flexible elements (N.P. Behtereva), the therapy led to an unbalance of SPC, "functional release" of neurons and redistribution of their functions to provide other activities, the formation of new interneuronal connections. Taking into account the functional variability of neurons (S.V. Medvedev), blocking neuromuscular transmission in spastic muscles leads to a reduction of abnormal afferent and efferent hyperactivity of motor and sensory neuronal circuits, which releases the brain for other activities. This allows to consider botulinotherapy of pharmacoresistant muscle spasticity in patients in VS and minimal consciousness, not only as a symptomatic treatment, but also as a "indirect neuroprotection".
Asunto(s)
Encéfalo/fisiopatología , Neuronas , Estado Vegetativo Persistente/fisiopatología , Estado de Conciencia/fisiología , Humanos , Movimiento , Espasticidad Muscular/fisiopatología , Neuronas/patología , Neuronas/fisiologíaRESUMEN
In the present article the features of the functional activity of the anterior cingulate cortex (ACC), a key element of neuroanatomical brain system of an error detection, in drug-resistant forms of obsessive-compulsive disorder (OCD) are discussed on a basis of both original and literature data. Available data indicate the presence of functional deficit in the ACC during OCD. This allows to suggest that functions of the ACC in OCD patient are partially redistributed between other brain areas. Thus in contrast to the previously accepted notion, the ACC as the target ofstereotactic surgery for OCD is pathologically altered brain region. Probably this is the reason why stereotactic destruction of ACC does not lead to significant changes in the patient's psyche. The essence of the pathological reorganisation of the functional activity of the brain in OCD remains unclear and requires further investigation.
Asunto(s)
Mapeo Encefálico , Giro del Cíngulo/fisiopatología , Trastorno Obsesivo Compulsivo , Resistencia a Medicamentos/fisiología , Giro del Cíngulo/diagnóstico por imagen , Humanos , Trastorno Obsesivo Compulsivo/tratamiento farmacológico , Trastorno Obsesivo Compulsivo/fisiopatología , Trastorno Obsesivo Compulsivo/psicología , Trastorno Obsesivo Compulsivo/cirugía , Radiografía , Técnicas EstereotáxicasRESUMEN
Live and inactivated vaccines are currently produced using virus reassortants originating from various gene donors of internal proteins. Based on the pandemic virus A/Hong Kong/1/68 (H3N2), a cold-adapted thermo-sensitive strain A/Hong Kong/1/68/162/35 was generated. It is distinguished for its high reproductive capacity (9-9.5 lg EID50), and hemagglutinating activity (1:1024-1:2048). The strain has ts and ca phenotype: reproductive capacity at t = 39 degrees C is 1.0 lg EID50; at t = 26 degrees C, 8.5 lg EID50. A total of 16 mutations have emerged from comprehensive sequencing of the virus genome. Among them 10 mutations were located in the genes of polymerase complex and NP, with respective amino-acid substitutions. The stability of strain characteristics, such as attenuation to humans and high reproductive capacity, were confirmed by repeated sequencing of the genome after tenfold passing of the virus in chicken embryos. Reassortants of the strain A/Hong Kong/1/68/162/35 with the wild-type viruses have inherited useful features of donor virus.
Asunto(s)
Subtipo H3N2 del Virus de la Influenza A , Vacunas contra la Influenza/genética , Gripe Humana , Vacunas Atenuadas , Frío , Humanos , Subtipo H3N2 del Virus de la Influenza A/genética , Subtipo H3N2 del Virus de la Influenza A/inmunología , Gripe Humana/genética , Gripe Humana/prevención & control , Gripe Humana/virología , Mutación , Virus Reordenados/genética , Temperatura , Proteínas Virales/genéticaRESUMEN
Influenza reassortant viruses A/SPb/HK/09(H1N1), A/Astana/HK/2009 (H5N1), A/Otar/HK/2010(H3N8), and A/Perth/ HK/2011(H3N2), carrying surface antigens of different subtypes, were constructed on the basis of new potential unified donor strain A/HK/1/68/162/35(H3N2). The virulence and reproduction activity of the obtained reassortants were tested. The safety of the candidate live and inactivated influenza vaccines produced from the reassortant viruses was demonstrated. The study demonstrates that A/HK/1/68/162/35 can be used as a unified donor for attenuated and high-yield vaccine reassortants.
Asunto(s)
Vacunas contra la Influenza , Gripe Humana , Vacunas Atenuadas , Vacunas de Productos Inactivados , Animales , Humanos , Subtipo H1N1 del Virus de la Influenza A/genética , Subtipo H1N1 del Virus de la Influenza A/inmunología , Subtipo H1N1 del Virus de la Influenza A/patogenicidad , Subtipo H3N2 del Virus de la Influenza A/genética , Subtipo H3N2 del Virus de la Influenza A/inmunología , Subtipo H3N2 del Virus de la Influenza A/patogenicidad , Subtipo H3N8 del Virus de la Influenza A/genética , Subtipo H3N8 del Virus de la Influenza A/inmunología , Subtipo H3N8 del Virus de la Influenza A/patogenicidad , Subtipo H5N1 del Virus de la Influenza A/genética , Subtipo H5N1 del Virus de la Influenza A/inmunología , Subtipo H5N1 del Virus de la Influenza A/patogenicidad , Vacunas contra la Influenza/genética , Gripe Humana/genética , Gripe Humana/inmunología , Gripe Humana/prevención & control , Gripe Humana/virología , Ratones , Vacunas Atenuadas/genética , Vacunas Atenuadas/inmunología , Vacunas de Productos Inactivados/genética , Vacunas de Productos Inactivados/inmunología , Replicación Viral/genéticaRESUMEN
The aim of the present research was to study the deliberate deception. Event related functional magnetic resonance (fMRI) imaging technique was used to assess the changes in functional brain activity by virtue of recording blood oxygen level dependant signal (BOLD-signal). 12 right-handed healthy volunteers aged 19-44 participated in the study. BOLD images were acquired in three different experimental trials. There were deliberate deception, manipulative honest and control truthful trials (catch trials). The main finding of the present study is that the deliberate deception and manipulative honest actions in comparison with instructed truthful responding was characterized by BOLD signal increase within the anterior cingulated cortex (ACC), frontal and parietal areas as well. Comparison of present fMRI data with results demonstrated in our previous research implemented with event related potentials technique points to the involvement of the brain mechanism of error detection to brain processing of deliberate deception.
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Mapeo Encefálico , Decepción , Detección de Mentiras/psicología , Oxígeno/sangre , Adulto , Humanos , Imagen por Resonancia Magnética/métodosRESUMEN
AIM: Study of specter of low-manifest infections (LMI) with central nervous system (CNS) damage and their role in patients in prolonged unconscious state (PUS) of noninflammatory etiology. MATERIALS AND METHODS: 32 patients (23 male, 9 female; age 14-58) in PUS of various etiology were examined. The main group (18 patients) received therapy against all infectious diseases including LMI; control group (14 patients)--only against common and nosocomial microflora. Patients were immunologically, infectologically and neurologically examined in dynamic. The data obtained were treated by using STATISTICA for Windows (version 5.5). RESULTS: Significant differences in immune and infectologic status depending on the nature of primary CNS damage were not detected. Immunodeficiency was detected in all patients; 94% of patients had increased non-specific IgM and IgE. Among LMI agents Chlamydia spp. were predominant. Cultural and/or PCR methods detected this microorganism during the primary examination in cerebrospinal fluid samples in 56% patients and in blood samples in 56%; during the second diagnostics or autopsy--only in 13 and 25%, respectively. Detection of Bacteroides fragilis, Human Herpes Virus (HHV-6), Virus Epstein Barr (VEB), Cytomegalovirus (CMV) in cerebrospinal fluid, blood and on mucous membranes of nasopharynx and conjunctiva was grouped more frequently with the presence of Chlamydia spp. in the CNS (p < 0.05) than with other LMI agents. Sanation of CNS from LMI was significantly accompanied by regeneration of communicative activity in comparison with the control group. CONCLUSION: In patients with PUS high frequency of CNS infection by various LMI agents and primarily Chlamydia spp. should be considered. Sanation from LMI can become a "window" for effective neuro-regenerative treatment.
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Infecciones Bacterianas/diagnóstico , Infecciones del Sistema Nervioso Central/diagnóstico , Chlamydia/aislamiento & purificación , Coinfección , Inconsciencia/diagnóstico , Virosis/diagnóstico , Adolescente , Adulto , Antibacterianos/administración & dosificación , Antivirales/administración & dosificación , Infecciones Bacterianas/líquido cefalorraquídeo , Infecciones Bacterianas/tratamiento farmacológico , Infecciones Bacterianas/microbiología , Infecciones Bacterianas/virología , Bacteroides fragilis/genética , Bacteroides fragilis/aislamiento & purificación , Sistema Nervioso Central/microbiología , Sistema Nervioso Central/patología , Sistema Nervioso Central/virología , Infecciones del Sistema Nervioso Central/líquido cefalorraquídeo , Infecciones del Sistema Nervioso Central/tratamiento farmacológico , Infecciones del Sistema Nervioso Central/microbiología , Infecciones del Sistema Nervioso Central/virología , Chlamydia/genética , Citomegalovirus/genética , Citomegalovirus/aislamiento & purificación , ADN Bacteriano/análisis , ADN Viral/análisis , Femenino , Herpesvirus Humano 4/genética , Herpesvirus Humano 4/aislamiento & purificación , Herpesvirus Humano 6/genética , Herpesvirus Humano 6/aislamiento & purificación , Humanos , Masculino , Persona de Mediana Edad , Tipificación Molecular , Reacción en Cadena de la Polimerasa , Inconsciencia/líquido cefalorraquídeo , Inconsciencia/tratamiento farmacológico , Inconsciencia/microbiología , Inconsciencia/virología , Virosis/líquido cefalorraquídeo , Virosis/tratamiento farmacológico , Virosis/microbiología , Virosis/virologíaRESUMEN
Quantum computing can become scalable through error correction, but logical error rates only decrease with system size when physical errors are sufficiently uncorrelated. During computation, unused high energy levels of the qubits can become excited, creating leakage states that are long-lived and mobile. Particularly for superconducting transmon qubits, this leakage opens a path to errors that are correlated in space and time. Here, we report a reset protocol that returns a qubit to the ground state from all relevant higher level states. We test its performance with the bit-flip stabilizer code, a simplified version of the surface code for quantum error correction. We investigate the accumulation and dynamics of leakage during error correction. Using this protocol, we find lower rates of logical errors and an improved scaling and stability of error suppression with increasing qubit number. This demonstration provides a key step on the path towards scalable quantum computing.
RESUMEN
We study noise-induced switching of a system close to bifurcation parameter values where the number of stable states changes. For non-Gaussian noise, the switching exponent, which gives the logarithm of the switching rate, displays a non-power-law dependence on the distance to the bifurcation point. This dependence is found for Poisson noise. Even weak additional Gaussian noise dominates switching sufficiently close to the bifurcation point, leading to a crossover in the behavior of the switching exponent.
RESUMEN
We report the identification of a localized current structure inside the JET plasma. It is a field-aligned closed helical ribbon, carrying current in the same direction as the background current profile (cocurrent), rotating toroidally with the ion velocity (corotating). It appears to be located at a flat spot in the plasma pressure profile, at the top of the pedestal. The structure appears spontaneously in low density, high rotation plasmas, and can last up to 1.4 s, a time comparable to a local resistive time. It considerably delays the appearance of the first edge localized mode.