Robust quantum state transfer using tunable couplers

We analyze the transfer of a quantum state between two resonators connected by a superconducting transmission line. Nearly perfect state-transfer efficiency can be achieved by using adjustable couplers and destructive interference to cancel the back-reflection into the transmission line at the receiving coupler. We show that the transfer protocol is robust to parameter variations affecting the transmission amplitudes of the couplers. We also show that the effects of the Gaussian filtering, pulse-shape noise, and multiple reflections on the transfer efficiency are insignificant. However, the transfer protocol is very sensitive to frequency mismatch between the two resonators. Moreover, the tunable coupler we considered produces time-varying frequency detuning caused by the changing coupling. This detuning requires an active frequency compensation with an accuracy better than 90% to yield the transfer efficiency above 99%

Robust quantum state transfer using tunable couplers

We analyze the transfer of a quantum state between two resonators connected by a superconducting transmission line. Nearly perfect state-transfer efficiency can be achieved by using adjustable couplers and destructive interference to cancel the back-reflection into the transmission line at the receiving coupler. We show that the transfer protocol is robust to parameter variations affecting the transmission amplitudes of the couplers. We also show that the effects of the Gaussian filtering, pulse-shape noise, and multiple reflections on the transfer efficiency are insignificant. However, the transfer protocol is very sensitive to frequency mismatch between the two resonators. Moreover, the tunable coupler we considered produces time-varying frequency detuning caused by the changing coupling. This detuning requires an active frequency compensation with an accuracy better than 90% to yield the transfer efficiency above 99%

Propene oligomerization using Alkali metal- and nickel-exchanged mesoporous aluminosilicate catalysts

A series of alkali metal- and nickel-exchanged Al-MCM-41 catalysts were prepared via aqueous ion exchange and then investigated for gas-phase oligomerization of propene at 453 K and near ambient pressures. All catalysts were active and produced oligomers with >98% selectivity. The highest activities per Ni2+ cation were observed when the cations were highly dispersed as a consequence of either lowering the Ni loading for a fixed MCM-41 Si/Al ratio or by decreasing the concentration of exchangeable sites within the material by increasing the MCM-41 Si/Al ratio at a fixed Ni loading. The identity of the alkali metal cation had no significant effect on the catalytic activity or degree of dimer branching, except for the sample containing Cs + cations, where the decreased pore volume resulted in a lower catalyst activity and slightly more linear dimer products. Comparison of Ni-MCM-41 prepared with and without Na+ cations showed that a higher yield of oligomers could be achieved when Na+ cations are present because of partial removal of strong Brønsted acid sites. For the same reaction conditions, Ni-Na-MCM-41 was more than twice as active as smaller-pored Ni-Na-X zeolites, demonstrating that the activity of Ni2+ cations increases with the increasing free volume near the site. This effect of free volume on the activity of Ni2+ cations was further confirmed by comparing the activities of Ni-Na-X, Ni-Na-MCM-41, Ni-Na-MCM-48, and Ni-Na-SBA-15 with respect to pore size. © 2013 American Chemical Society

Propene oligomerization using Alkali metal- and nickel-exchanged mesoporous aluminosilicate catalysts

A series of alkali metal- and nickel-exchanged Al-MCM-41 catalysts were prepared via aqueous ion exchange and then investigated for gas-phase oligomerization of propene at 453 K and near ambient pressures. All catalysts were active and produced oligomers with >98% selectivity. The highest activities per Ni2+ cation were observed when the cations were highly dispersed as a consequence of either lowering the Ni loading for a fixed MCM-41 Si/Al ratio or by decreasing the concentration of exchangeable sites within the material by increasing the MCM-41 Si/Al ratio at a fixed Ni loading. The identity of the alkali metal cation had no significant effect on the catalytic activity or degree of dimer branching, except for the sample containing Cs + cations, where the decreased pore volume resulted in a lower catalyst activity and slightly more linear dimer products. Comparison of Ni-MCM-41 prepared with and without Na+ cations showed that a higher yield of oligomers could be achieved when Na+ cations are present because of partial removal of strong Brønsted acid sites. For the same reaction conditions, Ni-Na-MCM-41 was more than twice as active as smaller-pored Ni-Na-X zeolites, demonstrating that the activity of Ni2+ cations increases with the increasing free volume near the site. This effect of free volume on the activity of Ni2+ cations was further confirmed by comparing the activities of Ni-Na-X, Ni-Na-MCM-41, Ni-Na-MCM-48, and Ni-Na-SBA-15 with respect to pore size. © 2013 American Chemical Society

Selective propene oligomerization with nickel(II)-based metal-organic frameworks

Two Ni2+-containing metal-organic frameworks, Ni 2(dobdc) and Ni2(dobpdc), are shown to be active for the oligomerization of propene in the gas phase. The metal-organic frameworks exhibit activity comparable to Ni2+-exchanged aluminosilicates but maintain high selectivity for linear oligomers. Thus, these frameworks should enable the high yielding synthesis of linear propene oligomers for use in detergent and diesel fuel applications. © 2014 American Chemical Society

Selective propene oligomerization with nickel(II)-based metal-organic frameworks

Two Ni2+-containing metal-organic frameworks, Ni 2(dobdc) and Ni2(dobpdc), are shown to be active for the oligomerization of propene in the gas phase. The metal-organic frameworks exhibit activity comparable to Ni2+-exchanged aluminosilicates but maintain high selectivity for linear oligomers. Thus, these frameworks should enable the high yielding synthesis of linear propene oligomers for use in detergent and diesel fuel applications. © 2014 American Chemical Society

Dihydropyridine Ca(2+) channel antagonists and agonists block Kv4.2, Kv4.3 and Kv1.4 K(+) channels expressed in HEK293 cells

1. We have determined the molecular basis of nicardipine-induced block of cardiac transient outward K(+) currents (I(to)). Inhibition of I(to) was studied using cloned voltage-dependent K(+) channels (Kv) channels, rat Kv4.3L, Kv4.2, and Kv1.4, expressed in human embryonic kindey cell line 293 (HEK293) cells. 2. Application of the dihydropyridine Ca(2+) channel antagonist, nicardipine, accelerated the inactivation rate and reduced the peak amplitude of Kv4.3L currents in a concentration-dependent manner (IC(50): 0.42 μM). The dihydropyridine (DHP) Ca(2+) channel agonist, Bay K 8644, also blocked this K(+) current (IC(50): 1.74 μM). 3. Nicardipine (1 μM) slightly, but significantly, shifted the voltage dependence of activation and steady-state inactivation to more negative potentials, and also slowed markedly the recovery from inactivation of Kv4.3L currents. 4. Coexpression of K(+) channel-interacting protein 2 (KChIP2) significantly slowed the inactivation of Kv4.3L currents as expected. However, the features of DHP-induced block of K(+) current were not substantially altered. 5. Nicardipine exhibited similar block of Kv1.4 and Kv4.2 channels stably expressed in HEK293 cells; IC(50)'s were 0.80 and 0.62 μM, respectively. 6. Thus, at submicromolar concentrations, DHP Ca(2+) antagonist and agonist inhibit Kv4.3L and have similar inhibiting effects on other components of cardiac I(to), Kv4.2 and Kv1.4