We propose short and robust directional couplers designed by shortcuts to adiabaticity, based on Lewis-Riesenfeld invariant theory. The design of directional couplers is discussed by combining invariant-based inverse engineering and perturbation theory. The error sensitivity of the coupler is minimized by optimizing the evolution of dynamical invariant with respect to coupling coefficient/input wavelength variations. The proposed robust coupler devices are verified with beam propagation simulations.
We propose fast and robust mode conversion in multimode waveguides based on Lewis-Riesenfeld invariant theory. The design of mode converters using the multimode driving for dynamical invariant is discussed. Computer-generated planar holograms are used to mimic the shaped pulses driving the states in three-level quantum systems. We show that the invariant-based inverse engineering scheme reduces mode converter length as compared to the common adiabatic scheme.
Sending multiple messages on qubits encoded in different vibrational modes of cold atoms or ions along a transmission waveguide requires to merge first and then separate the modes at input and output ends. Similarly, different qubits can be stored in the modes of a trap and be separated later. We design the fast splitting of a harmonic trap into an asymmetric double well so that the initial ground vibrational state becomes the ground state of one of two final wells, and the initial first excited state becomes the ground state of the other well. This might be done adiabatically by slowly deforming the trap. We speed up the process by inverse engineering a double-function trap using dynamical invariants. The separation (demultiplexing) followed by an inversion of the asymmetric bias and then by the reverse process (multiplexing) provides a population inversion protocol based solely on trap reshaping. Introduction.-One of the main goals of atomic physics is to achieve an exhaustive control of atomic states and dynamics [1]. The ultra-cold domain is particularly suitable for this aim as it provides a rich scenario of quantum states and phenomena. Atom optics and atomtronics [2] intend to manipulate cold atoms in circuits and devices for applications in metrology, quantum information, or fundamental science. These devices are frequently inspired by electronics (e.g. the atom diode [3,4], the transistor [2], atom chips [5]), or optics (e.g. beam splitters [6], or multiplexing [7,8]).In this paper we shall focus on a cold-atom realization of multiplexing, a basic process in modern telecommunications. Multiplexing is the transmission of different messages via a single physical medium. A multiplexer combines signals from several emitters into a single medium whereas a demultiplexer performs the reverse operation. The concept of multiplexing is relevant for quantum information processing (for its use in quantum repeaters see [9,10], or for trapped ions [11]). We envision here optical or magnetic waveguides for atoms holding several transverse orthogonal modes [12][13][14][15]. If the qubit is encoded in the internal state of the atom, several qubits may be carried out simultaneously by different modes. To develop such a quantum-information architecture, fast mul-
Cilostazol is an anti-platelet agent with vasodilatory activity that acts by increasing intracellular concentrations of cAMP. Recent reports have suggested that cilostazol may promote angiogenesis. In the present study, we have investigated the effect of cilostazol in promoting angiogenesis and vasculogenesis in a hindlimb ischaemia model and have also examined its potential mechanism of action in vitro and in vivo. We found that cilostazol treatment significantly increased colony formation by human early EPCs (endothelial progenitor cells) through a mechanism involving the activation of cAMP/PKA (protein kinase A), PI3K (phosphoinositide 3-kinase)/Akt/eNOS (endothelial NO synthase) and ERK (extracellular-signal-regulated kinase)/p38 MAPK (mitogen-activated protein kinase) signalling pathways. Cilostazol also enhanced proliferation, chemotaxis, NO production and vascular tube formation in HUVECs (human umbilical vein endothelial cells) through activation of multiple signalling pathways downstream of PI3K/Akt/eNOS. Cilostazol up-regulated VEGF (vascular endothelial growth factor)-A165 expression and secretion of VEGF-A in HUVECs through activation of the PI3K/Akt/eNOS pathway. In a mouse hindlimb ischaemia model, recovery of blood flow ratio (ipsilateral/contralateral) 14 days after surgery was significantly improved in cilostazol-treated mice (10 mg/kg of body weight) compared with vehicle-treated controls (0.63±0.07 and 0.43±0.05 respectively, P<0.05). Circulating CD34+ cells were also increased in cilostazol-treated mice (3614±670 compared with 2151±608 cells/ml, P<0.05). Expression of VEGF and phosphorylation of PI3K/Akt/eNOS and ERK/p38 MAPK in ischaemic muscles were significantly enhanced by cilostazol. Our data suggest that cilostazol produces a vasculo-angiogenic effect by up-regulating a broad signalling network that includes the ERK/p38 MAPK, VEGF-A165, PI3K/Akt/eNOS and cAMP/PKA pathways.
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