Controlling coherent interaction at avoided crossings is at the heart of quantum information processing. The regime between sudden switches and adiabatic transitions is characterized by quantum superpositions that enable interference experiments. Here, we implement periodic passages at intermediate speed in a GaAs-based two-electron charge qubit and observe Landau-Zener-Stückelberg-Majorana (LZSM) quantum interference of the resulting superposition state. We demonstrate that LZSM interferometry is a viable and very general tool to not only study qubit properties but beyond to decipher decoherence caused by complex environmental influences. Our scheme is based on straightforward steady state experiments. The coherence time of our two-electron charge qubit is limited by electron-phonon interaction. It is much longer than previously reported for similar structures.LZSM interferometry is a double-slit kind experiment which, in principle, can be realized with any qubit, while the specific measurement protocol might vary. Our system is a charge qubit based on two-electron states in a lateral double quantum dot (DQD) embedded in a twodimensional electron system (2DES) (Fig. 1). Source and drain leads at chemical potentials µ S,D , each tunnel coupled to one dot, allow current flow by single-electron tunneling. Applying the voltage V = (µ S − µ D )/e = 1 mV across the DQD (Fig. 1B) we use this current to detect the steady-state properties of the driven system. We interprete the singlets, S 11 (one electron in each dot) and S 20 (two electrons in the left dot), as qubit states. They form an avoided crossing (Fig. 1C), described by the Hamiltonianwhere we consider a variable energy detuning (t) and a constant inter-dot tunnel coupling tuned to ∆ 13 µeV, corresponding to a clock speed of ∆/h 3.1 GHz, where h is the Planck constant. Let us first discuss a single sweep through the avoided crossing at = 0: as shown back in 1932 independently by Landau, Zener, Stckelberg, and Majorana it brings the qubit into a superposition state [1][2][3][4], the electronic analog to the optical beam splitter. The probability to remain in the initial qubit state, P LZ = exp(−π∆ 2 /2 v), thereby grows with the velocity v = d /dt, here assumed to be constant [1][2][3][4]. Because the relative phase between the split wavepackets depends on their energy evolutions, repeated passages by a periodic modulation (t) =¯ +A cos(Ωt), give rise to so-called LZSM quantum interference [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. We present a breakthrough which * These authors contributed equally to this work.makes LZSM interferometry a powerful tool: it is based on systematic measurements together with a realistic model, which explicitly includes the noisy environment. We demonstrate how to decipher the detailed qubit dynamics and directly determine its decoherence time T 2 based on straightforward steady state measurements. Keeping the experiment simple we detect the dccurrent I through the DQD. It involves electron tunneling giving rise to the confi...

The current paper aims to identify the antecedents of social entrepreneurial intention formation. Applying the theory of planned behavior on an international sample of 159 entrepreneurial volunteers in a corporate framework, we find positive relationships between empathy, perceived social norms, self-efficacy, perceived collective efficacy, and social entrepreneurial intentions with mediation by perceived desirability and perceived feasibility. Overall, we contribute to the upcoming domain of social entrepreneurship research by investigating the individual and environmental antecedents of social entrepreneurial action in a corporate setting.

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g Gamma interferon (IFN-␥) regulates immune defenses against viruses, intracellular pathogens, and tumors by modulating cell proliferation, migration, invasion, and vesicle trafficking processes. The large GTPase guanylate binding protein 1 (GBP-1) is among the cellular proteins that is the most abundantly induced by IFN-␥ and mediates its cell biologic effects. As yet, the molecular mechanisms of action of GBP-1 remain unknown. Applying an interaction proteomics approach, we identified actin as a strong and specific binding partner of GBP-1. Furthermore, GBP-1 colocalized with actin at the subcellular level and was both necessary and sufficient for the extensive remodeling of the fibrous actin structure observed in IFN-␥-exposed cells. These effects were dependent on the oligomerization and the GTPase activity of GBP-1. Purified GBP-1 and actin bound to each other, and this interaction was sufficient to impair the formation of actin filaments in vitro, as demonstrated by atomic force microscopy, dynamic light scattering, and fluorescence-monitored polymerization. Cosedimentation and band shift analyses demonstrated that GBP-1 binds robustly to globular actin and slightly to filamentous actin. This indicated that GBP-1 may induce actin remodeling via globular actin sequestering and/or filament capping. These results establish GBP-1 as a novel member within the family of actin-remodeling proteins specifically mediating IFN-␥-dependent defense strategies.

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