1,396 research outputs found
Frustration elimination for effective optical spins in coherent Ising machines
Frustration, that is, the impossibility to satisfy the energetic preferences
between all spin pairs simultaneously, underlies the complexity of many
fundamental properties in spin systems, including the computational hardness to
determine their ground states. Coherent Ising machines (CIM) have been proposed
as a promising analog computational approach to efficiently find different
degenerate ground states of large and complex Ising models. However, CIMs also
face challenges in solving frustrated Ising models: Frustration not only
reduces the probability to find good solutions, but it also prohibits to
leverage quantum effects in doing so. To circumvent these detrimental effects
of frustration, we show how frustrated Ising models can be mapped to
frustration-free CIM configurations by including ancillary modes and modifying
the coupling protocol used in current CIM designs. In our proposal, degenerate
optical parametric oscillator (DOPO) modes encode the ground state candidates
of the studied Ising model, while the ancillary modes enable the autonomous
transformation to a frustration-free Ising model that preserves the ground
states encoded in the DOPO modes. Such frustration elimination may empower
current CIMs to improve precision and to benefit from quantum effects in
dealing with frustrated Ising models.Comment: 6 pages, 3 figure
Coherent-cluster-state generation in networks of degenerate optical parametric oscillators
Cluster states are versatile quantum resources and an essential building
block for measurement-based quantum computing. The possibility to generate
cluster states in specific systems may thus serve as an indicator if and to
what extent these systems can be harnessed for quantum technologies and quantum
information processing in particular. Here, we apply this analysis to networks
of degenerate optical parametric oscillators (DOPOs), also called coherent
Ising machines (CIMs). CIMs are distinguished by their highly flexible coupling
capabilities, which makes it possible to use them, e.g., to emulate large spin
systems. As CIMs typically operate with coherent states (and superpositions
thereof), it is natural to consider cluster states formed by superpositions of
coherent states, i.e., coherent cluster states. As we show, such coherent
cluster states can, under ideal conditions, be generated in DOPO networks with
the help of beam splitters and classical pumps. Our subsequent numerical
analysis provides the minimum requirements for the generation of coherent
cluster states under realistic conditions. Moreover, we discuss how
nonequilibrium pumps can improve the generation of coherent cluster states. In
order to assess the quality of the cluster state generation, we map the
generated states to an effective spin space using modular variables, which
allows us to apply entanglement criteria tailored for spin-based cluster
states.Comment: 12 pages, 8 figure
Electronic coolers based on superconducting tunnel junctions: fundamentals and applications
International audienceThermo-electric transport at the nano-scale is a rapidly developing topic, in particular in superconductor-based hybrid devices. In this review paper, we first discuss the fundamental principles of electronic cooling in mesoscopic superconducting hybrid structures, the related limitations and applications. We review recent work performed in Grenoble on the effects of Andreev reflection, photonic heat transport, phonon cooling, as well as on an innovative fabrication technique for powerful coolers
High flux cold Rubidium atomic beam for strongly coupled Cavity QED
This paper presents a setup capable of producing a high-flux continuous beam
of cold rubidium atoms for cavity QED experiments in the regime of strong
coupling. A 2 MOT, loaded by rubidium getters in a dry film coated vapor
cell, fed a secondary moving-molasses MOT (MM-MOT) at a rate of 1.5 x
atoms/sec. The MM-MOT provided a continuous beam with tunable velocity. This
beam was then directed through the waist of a 280 m cavity resulting in a
Rabi splitting of more than +/- 10 MHz. The presence of sufficient number of
atoms in the cavity mode also enabled splitting in the polarization
perpendicular to the input. The cavity was in the strong coupling regime, with
parameters (g, , )/2 equal to (7, 3, 6)/ 2 MHz.Comment: Journal pape
Design and Vertical Tests of SPS-series Double-Quarter Wave (DQW) Cavity Prototypes for the HL-LHC Crab Cavity System
Crab crossing is essential for high-luminosity colliders. The High Luminosity
Large Hadron Collider (HL-LHC) will equip one of its Interaction Points (IP1)
with Double-Quarter Wave (DQW) crab cavities. A DQW cavity is a new generation
of deflecting RF cavities that stands out for its compactness and broad
frequency separation between fundamental and first high-order modes. The
deflecting kick is provided by its fundamental mode. Each HL-LHC DQW cavity
shall provide a nominal deflecting voltage of 3.4 MV, although up to 5.0 MV may
be required. A Proof-of-Principle (PoP) DQW cavity was limited by quench at 4.6
MV. This paper describes a new, highly optimized cavity, designated DQW
SPS-series, which satisfies dimensional, cryogenic, manufacturing and impedance
requirements for beam tests at SPS and operation in LHC. Two prototypes of this
DQW SPS-series were fabricated by US industry and cold tested after following
conventional SRF surface treatment. Both units outperformed the PoP cavity,
reaching a deflecting voltage of 5.3-5.9 MV. This voltage - the highest reached
by a DQW cavity - is well beyond the nominal voltage of 3.4 MV and may even
operate at the ultimate voltage of 5.0MVwith sufficient margin. This paper
covers fabrication, surface preparation and cryogenic RF test results and
implications
Two-Level Atom in an Optical Parametric Oscillator: Spectra of Transmitted and Fluorescent Fields in the Weak Driving Field Limit
We consider the interaction of a two-level atom inside an optical parametric
oscillator. In the weak driving field limit, we essentially have an atom-cavity
system driven by the occasional pair of correlated photons, or weakly squeezed
light. We find that we may have holes, or dips, in the spectrum of the
fluorescent and transmitted light. This occurs even in the strong-coupling
limit when we find holes in the vacuum-Rabi doublet. Also, spectra with a
sub-natural linewidth may occur. These effects disappear for larger driving
fields, unlike the spectral narrowing obtained in resonance fluorescence in a
squeezed vacuum; here it is important that the squeezing parameter tends to
zero so that the system interacts with only one correlated pair of photons at a
time. We show that a previous explanation for spectral narrowing and spectral
holes for incoherent scattering is not applicable in the present case, and
propose a new explanation. We attribute these anomalous effects to quantum
interference in the two-photon scattering of the system.Comment: 10 pages, 17 figures, submitted to Phys Rev
Glycaemic control and risk of incident urinary incontinence in women with Type 1 diabetes: results from the Diabetes Control and Complications Trial and Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study
AimsTo study the impact of glycaemic control on urinary incontinence in women who participated in the Diabetes Control and Complications Trial (DCCT; 1983â1993) and its observational followâup study, the Epidemiology of Diabetes Interventions and Complications (EDIC; 1994âpresent).MethodsStudy participants were women who completed, at both years 10 (2003) and 17 (2010) of the EDIC followâup, the urological assessment questionnaire (UroEDIC). Urinary incontinence was defined as selfâreported involuntary leakage of urine that occurred at least weekly. Incident urinary incontinence was defined as weekly urinary incontinence present at EDIC year 17 but not at EDIC year 10. Multivariable regression models were used to examine the association of incident urinary incontinence with comorbid prevalent conditions and glycaemic control (mean HbA1c over the first 10 years of EDIC).ResultsA total of 64 (15.3%) women with Type 1 diabetes (mean age 43.6 ± 6.3 years at EDIC year 10) reported incident urinary incontinence at EDIC year 17. When adjusted for clinical covariates (including age, DCCT cohort assignment, DCCT treatment arm, BMI, insulin dosage, parity, hysterectomy, autonomic neuropathy and urinary tract infection in the last year), the mean EDIC HbA1c was associated with increased odds of incident urinary incontinence (odds ratio 1.03, 95% CI 1.01â1.06 per mmol/mol increase; odds ratio 1.41, 95% CI 1.07â1.89 per % HbA1c increase).ConclusionsIncident urinary incontinence was associated with higher HbA1c levels in women with Type 1 diabetes, independent of other recognized risk factors. These results suggest the potential for women to modify their risk of urinary incontinence with improved glycaemic control. (Clinical Trials Registry no: NCT00360815 and NCT00360893).Whatâs new?Research to date has failed to show an association between glycaemic control and urinary incontinence (UI) in women with diabetes.We examined the relationship between HbA1c and UI using longitudinal data from the Diabetes Control and Complications Trial (DCCT) and its observational followâup, the Epidemiology of Diabetes Interventions and Complications (EDIC) study.Our findings show that the odds of UI increase with poor glycaemic control in women with Type 1 diabetes, independently of other wellâdescribed predictors of UI.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134490/1/dme13126.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134490/2/dme13126_am.pd
Direct measurement of three-body interactions
Three-body interactions have been measured among three charged colloidal
particles in deionized solvent. Two of the particles have been confined to an
optical line-trap while the third one was approached by means of a focused
laser beam. The experimentally determined three-body interactions are
attractive and roughly of the same magnitude and range as the
pair-interactions. In addition, numerical calculations have been performed,
which show good agreement with the experimental results
Risk factors associated with typhoid fever in children aged 2-16 years in Karachi, Pakistan
We analysed the data from the control group in a typhoid vaccine trial in Karachi to assess the differences in individual-, household-and cluster-level characteristics for developing typhoid fever. The annual incidence of typhoid in children aged 2-16 years in the control arm of the vaccine trial was 151/100 000 population. After adjustment, the risk of typhoid was lower with increasing age [risk ratio (RR) 0.89, 95% confidence interval (CI) 0.83-0.95], was higher with an increase in population density (RR 1.13, 95% CI 1.05-1.21) and was lower in the households using a safe drinking-water source (RR 0.63, 95% CI 0.41-0.99). Typhoid fever affects younger children living in areas of high population density and lack of access to safe water in Pakistan. A combination of environmental and biological interventions is required to prevent the continued epidemiological and economic impact of typhoid fever in high-risk areas of Pakistan
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