Statistical limits for entanglement swapping with semiconductor entangled photon sources

Semiconductor quantum dots are promising building blocks for quantum communication applications. Al- though deterministic, efficient, and coherent emission of entangled photons has been realized, implementing a practical quantum repeater remains outstanding. Here we explore the statistical limits for entanglement swapping with sources of polarization-entangled photons from the commonly used biexciton-exciton cascade. We stress the necessity of tuning the exciton fine structure, and explain why the often observed time evolution of photonic entanglement in quantum dots is not applicable for large quantum networks. We identify the critical, statistically distributed device parameters for entanglement swapping based on two sources. A numerical model for benchmarking the consequences of device fabrication, dynamic tuning techniques, and statistical effects is developed, in order to bring the realization of semiconductor-based quantum networks one step closer to reality. ©2022 American Physical Societ

Photoneutralization of charges in GaAs quantum dot based entangled photon emitters

Semiconductor-based emitters of pairwise photonic entanglement are a promising constituent of photonic quantum technologies. They are known for the ability to generate discrete photonic states on-demand with low multiphoton emission, near-unity entanglement fidelity, and high single photon indistinguishability. However, quantum dots typically suffer from luminescence blinking, lowering the efficiency of the source and hampering their scalable application in quantum networks. In this paper, we investigate and adjust the intermittence of the neutral exciton emission in a GaAs/AlGaAs quantum dot under two-photon resonant excitation of the neutral biexciton. We investigate the spectral and quantum optical response of the quantum dot emission to an additional wavelength tunable gate laser, revealing blinking caused by the intrinsic Coulomb blockade due to charge capture processes. Our finding demonstrates that the emission quenching can be actively suppressed by controlling the balance of free electrons and holes in the vicinity of the quantum dot and thereby significantly increasing the quantum efficiency by 30%. ©2022 American Physical Societ

2015 Research & Innovation Day Program

A one day showcase of applied research, social innovation, scholarship projects and activities.https://first.fanshawec.ca/cri_cripublications/1002/thumbnail.jp

High Molecular Weight Fibroblast Growth Factor-2 in the Human Heart Is a Potential Target for Prevention of Cardiac Remodeling

<div><p>Fibroblast growth factor 2 (FGF-2) is a multifunctional protein synthesized as high (Hi-) and low (Lo-) molecular weight isoforms. Studies using rodent models showed that Hi- and Lo-FGF-2 exert distinct biological activities: after myocardial infarction, rat Lo-FGF-2, but not Hi-FGF-2, promoted sustained cardioprotection and angiogenesis, while Hi-FGF-2, but not Lo-FGF-2, promoted myocardial hypertrophy and reduced contractile function. Because there is no information regarding Hi-FGF-2 in human myocardium, we undertook to investigate expression, regulation, secretion and potential tissue remodeling-associated activities of human cardiac (atrial) Hi-FGF-2. Human patient-derived atrial tissue extracts, as well as pericardial fluid, contained Hi-FGF-2 isoforms, comprising, respectively, 53%(±20 SD) and 68% (±25 SD) of total FGF-2, assessed by western blotting. Human atrial tissue-derived primary myofibroblasts (hMFs) expressed and secreted predominantly Hi-FGF-2, at about 80% of total. Angiotensin II (Ang II) up-regulated Hi-FGF-2 in hMFs, via activation of both type 1 and type 2 Ang II receptors; the ERK pathway; and matrix metalloprotease-2. Treatment of hMFs with neutralizing antibodies selective for human Hi-FGF-2 (neu-Ab^Hi-FGF-2) reduced accumulation of proteins associated with fibroblast-to-myofibroblast conversion and fibrosis, including α-smooth muscle actin, extra-domain A fibronectin, and procollagen. Stimulation of hMFs with recombinant human Hi-FGF-2 was significantly more potent than Lo-FGF-2 in upregulating inflammation-associated proteins such as pro-interleukin-1β and plasminogen-activator-inhibitor-1. Culture media conditioned by hMFs promoted cardiomyocyte hypertrophy, an effect that was prevented by neu-Ab^Hi-FGF-2<i>in vitro</i>. In conclusion, we have documented that Hi-FGF-2 represents a substantial fraction of FGF-2 in human cardiac (atrial) tissue and in pericardial fluid, and have shown that human Hi-FGF-2, unlike Lo-FGF-2, promotes deleterious (pro-fibrotic, pro-inflammatory, and pro-hypertrophic) responses <i>in vitro.</i> Selective targeting of Hi-FGF-2 production may, therefore, reduce pathological remodelling in the human heart.</p></div

Detection of Hi-FGF-2 in human atrial myofibroblasts.

<p><b>Panel (A)</b> shows two sets of western blots analyzing FGF-2 isoforms. The first set, (i), is a composite of two blots (separated by a broken line) and analyzes FGF-2 isoforms in hMF lysates (20 µg/lane), from atrial myofibroblast primary cultures obtained from 10 patients (patients 11–20), and correspondingly labeled as C11–20. The second set, (ii), also a composite of two blots separated by a broken line, analyzes FGF-2 isoforms in atrial tissue lysates from patients 11–20, and labelled T11–20 (50 µg/lane). The hMF blots or tissue blots were also probed for, respectively, β-tubulin (β-tub), or Troponin-T (TnT), as indicated. Following densitometry of the hMF blots, the % contribution of each FGF-2 isoform to the total FGF-2 signal was determined for each individual lane, and cumulative results (mean±SD) are included in graph form (n = 10). <b>In Panel (B)</b>, a western blot shows FGF-2 signals from 0.5 and 0.2 ng/lane of recombinant histidine tagged Lo-FGF-2 (FGF-2<i>^His</i>), atrial tissue lysates (T11, T15 and T17, loaded at 50 µg/lane), side by side with FGF-2 signals from lysates obtained from corresponding primary hMF cultures (C11, C15 and C17, loaded at 10 µg/lane). The graph shows comparisons between tissue and cell lysates for their relative total FGF-2 content, assessed by densitometry as optical density (O.D.) units (n = 3). Measurements corresponding to cell FGF-2 were multiplied by 5, to correct for the 5-fold difference in total protein loading. In both panels, comparisons between groups are indicated by brackets, where P>0.05 is marked as ns, while P<0.001, 0.01, are marked as ***, or **, respectively. <b>Panels C and D</b> show immunofluorescence images of hMFs stained for, (C), Hi-FGF-2 (green), as well as, (D), alpha smooth muscle actin (red) and nuclei (blue). White arrows point to cytosolic Hi-FGF-2; pink and pale- pink arrows arrows point to nuclear and nucleolar Hi-FGF-2, respectively. Grey sizing bars correspond to 20 µm.</p

Detection of Hi-FGF-2 in human atrial tissue.

<p><b>Panel (A)</b> shows representative western blot images of human atrial extracts (hA1, hA2, hA3, 50 µg/lane) probed for FGF-2 with an antibody detecting all FGF-2 isoforms. Expected migration of all human FGF-2 isoforms (34, 24, 22–22.5, and 18 kDa), corresponding to Hi- or Lo-FGF-2, is indicated by arrows; please note that the 34 kDa isoform is not detectable in tissue lysates. Western blots were also probed for cardiac troponin T (TnT) to verify equivalent loading of lanes. Samples hA1, hA2 were analyzed in small (8.3×5.5 cm²) 15% polyacrylamide gels, while hA3 was analyzed in a large (16×11.5 cm²) 15% polyacrylamide gel. The included graph shows percentage of each isoform over total FGF-2, where, n = 45; comparisons between groups are indicated by brackets, where *** and ** denote P<0.001, and P<0.01, respectively. <b>Panels (B) and (C)</b> show images from patient-derived serial atrial sections, subjected to (B) incubation with purified anti-Hi-FGF-2 antibodies followed by immunohistochemical visualization of antigen-antibody complexes (brown color) as well as nuclear staining (hematoxylin, blue), and (C) similar procedures as in B but without the anti-Hi-FGF-2 antibodies. Incubation with anti-Hi-FGF-2 antibody elicits extensive immunostaining, in what appears to be nuclear as well as cytosolic sites in cardiomyocytes; staining of non-cardiomyocytes located at the epicardium is indicated by arrows. <b>Panels (D) and (E)</b> are close-up images from human atrial tissue sections stained as in (B), showing cellular and subcellular distribution of Hi-FGF-2. <b>Panels (G) and (F)</b> show human atrial sections subjected to double-immunofluorescence staining for Hi-FGF-2 (green), and either vimentin (G, red), or desmin (F, red). In all images, yellow or pink arrows point, respectively, to nuclear or cytosolic sites within cardiomyocytes. Blue arrows in (D) point to small connective tissue cells, likely fibroblasts. Green arrows in (E) point to endothelial cells, lining a vessel. White arrows in (G) and (F) point to non-myocytes, found at or near the epicardial region. These cells are positive for vimentin, but not desmin. In (F), co-staining with desmin confirms presence of Hi-FGF-2 in atrial cardiomyocytes. Sizing bars in (B) or (D,E,F,G) correspond to 250 or 100 µM, respectively. Insets within panels G and F are shown in larger magnification in Fig S2.</p

Both AT-1R and AT-2R mediate the Ang II-induced ERK activation in hMFs.

<p>Panel A shows western blot of activated (phosphorylated) pERK, and total ERK, in hMFs stimulated for 30 minutes with with Ang II (lanes 1,2,3), Ang II + PD123319 (lanes 4,5,6), Ang II + Losartan (lanes 7,8,9), and Ang II +PD123319 +Losartan (lanes 10,11,12), in the absence (-) or presence (+) of neutralizing anti-FGF-2 antibodies (neu-Ab^FGF-2), as indicated. Please note that the western blot for pERK in the groups incubated with neu-Ab^FGF-2 is not directly comparable to the western blot for pERK in the groups incubated in the absence of neu-Ab^FGF-2 (different exposures). Panel B shows pERK/ERK ratios in the groups shown in panel A. Brackets show statistically significant differences between groups, where *, **, ***, correspond to P<0.05, 0.01, and 0.001, respectively.</p

Selective neutralization of extracellular human Hi-FGF-2 attenuates expression of pro-fibrotic proteins.

<p><b>Panel A</b>. Western blots showing the effect of incubation with either control antibodies (Cont-Ab, 20 µg/ml, lanes 1,2,3), or anti-Hi-FGF-2 antibodies (Neu-Ab^Hi-FGF-2, 20 µg/ml, lanes 4,5,6) on the accumulation of α-SMA, procollagen, SMemb, EDA-Fibronectin (EDA-FN), β-tubulin, and GAPDH, by hMFs, as indicated. <b>Panels B</b>,<b>C</b>,<b>D</b> and <b>E</b> show corresponding quantitative (densitometry) data for α-SMA, procollagen, SMemb, EDA-Fibronectin (EDA-FN), as indicated (±SEM). Incubation with Neu-Ab^Hi-FGF-2 significantly decreased expression of α-SMA, procollagen, SMemb and EDA-Fibronectin, without having any effect on GAPDH or β-tubulin. Brackets show comparisons between groups, where *, **, *** correspond to P<0.05, <0.01, <0.001; n = 3/group.</p

Human Hi-FGF-2 exerts pro-hypertrophic effect.

<p><b>Panel A.</b> Neonatal rat cardiomyocyte cell surface area (normalized, assigning a value of 1 in control, untreated samples) is shown in response to stimulation with Endothelin 1 (ET-1), serving as a positive control, and a recombinant human Hi-FGF-2 preparation (10 ng protein/ml), n = 320 myocytes/group. CM denotes conditioned medium obtained from unstimulated hMFs while CM* denotes conditioned medium from Ang II-stimulated hMFs. ET-1, recombinant human Hi-FGF-2, as well as CM* (but not CM, or Ang II added at 100 nM) increased myocyte cell surface area significantly. <b>Panel B</b>. Cardiomyocyte cell surface area (normalized) is shown as a function of incubation with CM, CM*or CM* supplemented with neutralizing antibodies to total FGF-2 (neu-Ab^FGF-2), as indicated; n = 480 cells/group. Neutralization of total FGF-2 eliminated the ability of CM* to increase myocytes cell surface area compared to CM. <b>Panel C.</b> Protein synthesis (³H-Leucine incorporation) of cardiomyocytes incubated with CM, CM*, and CM* supplemented with 20 µg/ml neutralizing anti-Hi-FGF-2 antibodies (CM* +neu-Ab^Hi-FGF-2). Neutralization of Hi-FGF-2 eliminated the ability of CM* to increase protein synthesis of cardiomyocytes compared to CM; n = 5 plates/group. <b>D</b>. Cardiomyocyte cell surface area (normalized) is shown as a function of incubation with CM, CM*, and CM* +neu-Ab ^Hi-FGF-2. Neutralization of Hi-FGF-2 eliminated the ability of CM* to increase surface area of cardiomyocytes compared to CM; n = 480/group. Please note that for the experiments shown in B,C,D panels the conditioned media in the first two groups (CM, CM*) were supplemented with non-specific rabbit IgG, at 20 µg/ml. <b>E</b>. Representative images of cardiomyocytes stained for anti-N-cadherin (green), alpha-actinin (red) and nuclei (blue), and incubated with CM, CM*, and CM* +neu-Ab (FGF-2). Sizing bar in (iii) coresponds to 100 µM. In all graphs, brackets show comparison between groups, where *, **, ***, ns correspond to P<0.05, <0.01, <0.001, or P>0.05.</p