Coherent optical nanotweezers for ultracold atoms.

There has been a recent surge of interest and progress in creating subwavelength free-space optical potentials for ultracold atoms. A key open question is whether geometric potentials, which are repulsive and ubiquitous in the creation of subwavelength free-space potentials, forbid the creation of narrow traps with long lifetimes. Here, we show that it is possible to create such traps. We propose two schemes for realizing subwavelength traps and demonstrate their superiority over existing proposals. We analyze the lifetime of atoms in such traps and show that long-lived bound states are possible. This work allows for subwavelength control and manipulation of ultracold matter, with applications in quantum chemistry and quantum simulation.

Floquet engineering of optical lattices with spatial features and periodicity below the diffraction limit.

Floquet engineering or coherent time periodic driving of quantum systems has been successfully used to synthesize Hamiltonians with novel properties. In ultracold atomic systems, this has led to experimental realizations of artificial gauge fields, topological band structures, and observation of dynamical localization, to name just a few. Here we present a Floquet-based framework to stroboscopically engineer Hamiltonians with spatial features and periodicity below the diffraction limit of light used to create them, by time-averaging over various configurations of a 1D optical Kronig-Penney (KP) lattice. The KP potential is a lattice of narrow subwavelength barriers spaced by half the optical wavelength ( λ / 2 ) and arises from the nonlinear optical response of the atomic dark state. Stroboscopic control over the strength and position of this lattice requires time-dependent adiabatic manipulation of the dark-state spin composition. We investigate adiabaticity requirements, and shape our time-dependent light fields to respect these requirements. We apply this framework to show that a λ / 4 -spaced lattice can be synthesized using realistic experimental parameters. As an example, we discuss mechanisms that limit lifetimes in these lattices, explore candidate systems with their limitations, and study adiabatic loading into the ground band of these lattices.

Dark State Optical Lattice with a Subwavelength Spatial Structure.

We report on the experimental realization of a conservative optical lattice for cold atoms with a subwavelength spatial structure. The potential is based on the nonlinear optical response of three-level atoms in laser-dressed dark states, which is not constrained by the diffraction limit of the light generating the potential. The lattice consists of a one-dimensional array of ultranarrow barriers with widths less than 10 nm, well below the wavelength of the lattice light, physically realizing a Kronig-Penney potential. We study the band structure and dissipation of this lattice and find good agreement with theoretical predictions. Even on resonance, the observed lifetimes of atoms trapped in the lattice are as long as 44 ms, nearly 10^{5} times the excited state lifetime, and could be further improved with more laser intensity. The potential is readily generalizable to higher dimensions and different geometries, allowing, for example, nearly perfect box traps, narrow tunnel junctions for atomtronics applications, and dynamically generated lattices with subwavelength spacings.

Attenuated post-exercise heart rate recovery in patients with systemic lupus erythematosus: the role of disease severity and beta-blocker treatment.

Objective Sinus tachycardia is frequently reported in systemic lupus erythematosus (SLE), while there are limited data on post-exercise ability to slow heart rate (i.e. heart rate recovery, HRR) in this group of patients. Methods We studied consecutive 70 patients with SLE and 30 healthy controls. All examined individuals underwent detailed clinical examination, echocardiography, Holter monitoring with heart rate variability and treadmill stress test using Bruce's protocol. HRR values were calculated as the difference between maximum HR during exercise and HR at the first (HRR1) and third (HRR3) minute of rest. Individuals with coronary artery disease, diabetes mellitus and suspected pulmonary hypertension were excluded from further analysis ( n = 15). Results Fifty-five SLE patients were eligible for this study: aged 41.5 ± 12.4 years, 87.3% women, SLICC/ACR-DI score 3.58 ± 1.85. In the SLE group 36.4% patients received beta-blockers, usually for previously detected sinus tachycardia and/or arterial hypertension. Mean HRR1 (36.9 ± 12.6 vs 49.5 ± 18.6, p = 0.0004) and HRR3 (55.5 ± 14.3 vs 69.2 ± 16.4, p = 0.0001) were significantly lower in SLE than in healthy individuals. Significantly negative correlations between SLICC/ACR-DI score and HRR1 ( r = -0.299, p = 0.01), HRR3 ( r = -0.361, p = 0.001) and exercise capacity ( r = -0.422, p < 0.0001) were revealed. Additionally, beta-blocker treatment was also revealed to alter significantly HRR1, HRR3 and exercise capacity in SLE. Conclusion Patients with SLE are characterized by attenuated HRR after exercise. In our study impaired HRR was associated with disease severity and beta-blocker treatment and probably with disease duration. The use of HRR assessment in SLE can be used as an additional marker of cardiac autonomic nervous system dysfunction.

Enhancement of Rydberg-mediated single-photon nonlinearities by electrically tuned Förster resonances.

Mapping the strong interaction between Rydberg atoms onto single photons via electromagnetically induced transparency enables manipulation of light at the single-photon level and few-photon devices such as all-optical switches and transistors operated by individual photons. Here we demonstrate experimentally that Stark-tuned Förster resonances can substantially increase this effective interaction between individual photons. This technique boosts the gain of a single-photon transistor to over 100, enhances the non-destructive detection of single Rydberg atoms to a fidelity beyond 0.8, and enables high-precision spectroscopy on Rydberg pair states. On top, we achieve a gain larger than 2 with gate photon read-out after the transistor operation. Theory models for Rydberg polariton propagation on Förster resonance and for the projection of the stored spin-wave yield excellent agreement to our data and successfully identify the main decoherence mechanism of the Rydberg transistor, paving the way towards photonic quantum gates.

Coulomb Bound States of Strongly Interacting Photons.

We show that two photons coupled to Rydberg states via electromagnetically induced transparency can interact via an effective Coulomb potential. This interaction gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasibound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb potential, thus obtaining a photonic analogue of the hydrogen atom. Under certain conditions, the wave function resembles that of a diatomic molecule in which the two polaritons are separated by a finite "bond length." These states propagate with a negative group velocity in the medium, allowing for a simple preparation and detection scheme, before they slowly decay to pairs of bound Rydberg atoms.

Dipolar Dephasing of Rydberg D-State Polaritons.

We experimentally study the effects of the anisotropic Rydberg interaction on D-state Rydberg polaritons slowly propagating through a cold atomic sample. We observe the interaction-induced dephasing of Rydberg polaritons at very low photon input rates into the medium. We develop a model combining the propagation of the two-photon wave function through our system with nonperturbative calculations of the anisotropic Rydberg interaction to show that the observed effect can be attributed to pairwise interaction of individual Rydberg polaritons at distances larger than the Rydberg blockade.

Assessment of systemic and pulmonary arterial remodelling in women with systemic sclerosis.

OBJECTIVES: Systemic sclerosis (SSc) leads to pulmonary circulation dysfunctionand there are some indications of systemic circulation impairment. We evaluated the influence of SSc on the elastic properties of large systemic arterial walls and potential correlations between systemic and pulmonary circulation involvement. METHOD: We examined 75 consecutive women (mean age 53.13±10.1 years) with confirmed SSc [mean disease duration (DD) 7.1±9.1 years] and 21 age-matched female volunteers (mean age 52.6±8.3 years, ns). Pulse wave velocity (PWV) and transthoracic echocardiography were performed. SSc patients were divided into two groups according to the median of DD: ≤3 years (39 patients) and >3 years (36 patients). RESULTS: Patients with DD>3 years had higher PWV than those with DD≤3 years and controls (log PWV: 2.23±0.23 vs. 2.13±0.16 and vs. 2.11±0.16 m/s; p=0.028 and 0.029, respectively). In addition, echocardiographic indices showed impaired right ventricular (RV) function in the patients with DD>3 years. Also in these SSc patients, PWV correlated with clinical and echocardiographic parameters of pulmonary circulation: age (r=0.64, p<0.0001), acceleration time of pulmonary ejection (AcT; r=-0.38, p=0.021), and tricuspid regurgitation peak gradient (TRPG; r=0.34, p=0.04). Multiple linear regression analysis showed that PWV was independently associated with DD (ß=0.22, p==0.02), AcT (ß=-0.215, p=0.03), and age (ß=0.44, p<0.001). CONCLUSIONS: In patients with SSc lasting more than 3 years, the disease is characterized by increased stiffness of the large systemic arteries. Longer duration of SSc leads simultaneously to the increased stiffness of the large systemic arteries and to the progressive impairment of RV function and its coupling to the pulmonary arterial bed.

Pro- and antiangiogenic markers in patients with pulmonary complications of systemic scleroderma.

Systemic sclerosis (SSc) is an autoimmune disorder characterized by skin and internal organs fibrosis and concomitant vascular abnormalities. Although SSc is considered mainly fibrosing disease, underlying vascular pathology plays a fundamental role in its pathogenesis. We have focused on positive and negative serum markers of angiogenesis and fibrosis (pigment epithelium-derived factor [PEDF], vascular endothelial growth factor [VEGF], and soluble VEGF receptor [sVEGFR]), in progressive SSc patients at baseline and after follow-up in relation to cardiopulmonary complications (systemic hypertension [HT], pulmonary arterial hypertension [PAH] and pulmonary fibrosis [PF]). VEGF and PEDF but not sVEGFR were reciprocally regulated in SSc progression. Moreover, VEGF/PEDF ratio significantly increased during follow up suggesting that it might be used as a biomarker of disease progression. No correlation between the studied markers and cardiopulmonary complications was observed. In conclusion, VEGF and PEDF level, and the VEGF/PEDF ratio are significantly changed in the course of SSc progression and these markers can be used to assess SSc activity.

Antiendothelial cells antibodies in patients with systemic sclerosis in relation to pulmonary hypertension and lung fibrosis.

Although scleroderma is generally considered a fibrosing disease, it is now recognized that the underlying vascular pathology is playing a fundamental role in its pathogenesis. The present study was aimed at testing the prevalence of anti-endothelial cell antibodies (AECA) in systemic scleroderma (SSc) patients with and without pulmonary hypertension (PH) and in relation to the presence of pulmonary fibrosis. Fifty four SSc patients (50 females and 4 male, mean age 55.7 ± 16.3 years) were prospectively screened. All patients underwent transthoracic echocardiography with the estimation of pulmonary artery pressure (PAP) and tricuspid regurgitant peak gradient (TRPG). All patients suspected to have pulmonary hypertension were referred for right heart catheterization. Restrictive lung disease was confirmed by HRCT. A healthy control group included (n = 27; 7 men and 20 women, mean age 49.8 ± 12.1 years). The study of AECA was performed using the indirect immunofluorescence method on commercially available human umbilical vein endothelial cells. The HRCT scans in patients with suspected interstitial lung disease revealed signs of lung fibrosis in 15 (out of the 36 examined patients). TRPG at rest of 31 mmHg was demonstrated in 14 (21%) patients. During cardiac catheterization, arterial PH was found in two patients. Resting venous PH was found in one patient and an excessive post capillary PAP elevation at rest was demonstrated in 11 patients. At the baseline, 14/54 patients (26%) were positive for AECA. In the control group, the frequency of the antibodies was 3/27 (11%). No statistical correlation between antibody titter and the presentation of the disease existed. AECA were highly prevalent in a subgroup of patients suffering from interstitial pulmonary fibrosis. Out of the 15 patients suffering from lung fibrosis, 7 were AECA positive. The presence of AECA correlated very well with antinuclear antibodies (ANA), but was not related to the profile of ANA. Our findings support evidence that endothelial cell damage is involved in SSc, as there was increased prevalence of circulating AECA of the IgG isotype in SSc patients. AECA may also be related to the complications of SSc, like pulmonary fibrosis.