Mechanistic And Synthetic Investigations In Sulfonyl Chemistry And Acyl Transfer

This thesis contains three chapters dealing with the organic chemistry of sulfonyl and carbonyl compounds. The first chapter describes the synthesis and rate studies of a series of {dollar}\beta{dollar}-methoxy sulfones and their unsubstituted parent compounds designed to test some basic ideas of the nature of the electronic effects of substituents in saturated systems. The substrates were designed to illustrate the effect of the change of the H{dollar}\sb\alpha{dollar}-C{dollar}\sb\alpha{dollar}-C{dollar}\sb\beta{dollar}-O dihedral angle on the rate of base-promoted H-D exchange reaction. The presence of a {dollar}\beta{dollar}-methoxy group affected the H-D exchange rates by factors varying from a few hundred to greater than ten thousands. This study leads to the conclusion that the effect of a {dollar}\beta{dollar}-alkoxy substituent cannot be accounted for by the conventional polar effect (i.e. inductive and field effects), but must involve a kinetic anomeric effect.;The second chapter describes synthesis, hydrolysis, and p{dollar}K\sb{lcub}\rm a{rcub}{dollar} determination of sulfonamides and sulfonimides. Ethane-1,2-disulfonimide has been synthesized for the first time. More than twenty other sulfonamides and sulfonimides were synthesized to examine the effect of ring strain and a stereoelectronic effect in acidities and hydrolysis rates. It has been found that the acidities of five-membered cyclic sulfonimides are one to two orders of magnitude greater than six-membered cyclic sulfonimides or acyclic sulfonimides. It has also been found that ethane-1,2-disulfonimide hydrolyses 430 times faster than its six-membered analogue, propane-1,3-disulfonimide, and 320 times faster than its open chain analogue, dimethanesulfonimide.;In the third chapter pH optimization in acyl transfer has been described. The reaction of amines with Ac{dollar}\sb2{dollar}O in water gave variable yields of the N-substituted acetamide. From the p{dollar}K\sb{lcub}\rm a{rcub}{dollar}\u27s of the amines and {dollar}k\sb{lcub}\rm w{rcub}{dollar} and {dollar}k\sb{lcub}\rm OH{rcub}{dollar} for Ac{dollar}\sb2{dollar}O, both {dollar}k\sb{lcub}\rm DN{rcub}{dollar} and {dollar}k\sb{lcub}\rm GB{rcub}{dollar} may be readily evaluated by fitting the pH-yield data to pH-yield or pH-product ratio profiles. The extent of general base catalysis is evidently dependent on the amount of steric hindrance and the pK{dollar}\sb{lcub}\rm a{rcub}{dollar} of the amine. The reactions of PhCOCl with PhCH{dollar}\sb2{dollar}NH{dollar}\sb2{dollar} and piperidine in aqueous solution show no sign of the general base assisted hydrolysis. A general equation for obtaining the maximum yield in competition with hydrolysis is presented and verified with the benzoylation and acetylation reactions

Finite-key analysis for quantum key distribution with discrete phase randomization

Quantum key distribution(QKD) allows two remote parties to share information-theoretic secret keys. Many QKD protocols assume the phase of encoding state can be continuous randomized from 0 to 2 pi, which, however, may be questionable in experiment. This is particularly the case in the recently proposed twin-field(TF) QKD, which has received a lot of attention, since it can increase key rate significantly and even beat some theoretical rate-loss limits. As an intuitive solution, one may introduce discrete phase-randomization instead of continuous one. However, a security proof for a QKD protocol with discrete phase-randomization in finite-key region is still missing. Here we develop a technique based on conjugate measurement and quantum state distinguishment to ana-lyze the security in this case. Our result shows that TF-QKD with reasonable number of discrete random phases, e.g. 8 phases from {0, pi/4, pi/2, ..., 7pi/4}, can achieve satisfactory performance. More importantly, as a the first proof for TF-QKD with discrete phase-randomization in finite-key region, our method is also applicable in other QKD protocols.Comment: 1 figures,20 page

Novel and Neuroprotective Tetranortriterpenoids from Chinese Mangrove Xylocarpus granatum Koenig

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Threshold-independent method for single-shot readout of spin qubits in semiconductor quantum dots

The single-shot readout data process is essential for the realization of high-fidelity qubits and fault-tolerant quantum algorithms in semiconductor quantum dots. However, the fidelity and visibility of the readout process is sensitive to the choice of the thresholds and limited by the experimental hardware. By demonstrating the linear dependence between the measured spin state probabilities and readout visibilities along with dark counts, we describe an alternative threshold-independent method for the single-shot readout of spin qubits in semiconductor quantum dots. We can obtain the extrapolated spin state probabilities of the prepared probabilities of the excited spin state through the threshold-independent method. Then, we analyze the corresponding errors of the method, finding that errors of the extrapolated probabilities cannot be neglected with no constraints on the readout time and threshold voltage. Therefore, by limiting the readout time and threshold voltage we ensure the accuracy of the extrapolated probability. Then, we prove that the efficiency and robustness of this method is 60 times larger than that of the most commonly used method. Moreover, we discuss the influence of the electron temperature on the effective area with a fixed external magnetic field and provide a preliminary demonstration for a single-shot readout up to 0.7 K/1.5T in the future.Comment: 18 pages, 6 figure

Flopping-mode spin qubit in a Si-MOS quantum dot

Spin qubits based on silicon metal-oxide semiconductor (Si-MOS) quantum dots (QDs) are promising platforms for large-scale quantum computers. To control spin qubits in QDs, electric dipole spin resonance (EDSR) has been most commonly used in recent years. By delocalizing an electron across a double quantum dots charge state, flopping-mode EDSR has been realized in Si/SiGe QDs. Here, we demonstrate a flopping-mode spin qubit in a Si-MOS QD via Elzerman single-shot readout. When changing the detuning with a fixed drive power, we achieve s-shape spin resonance frequencies, an order of magnitude improvement in the spin Rabi frequencies, and virtually constant spin dephasing times. Our results offer a route to large-scale spin qubit systems with higher control fidelity in Si-MOS QDs.Comment: 5 pages, 4 figure