73 research outputs found
Single Nuclear Spin Cavity QED
We constructed a cavity QED system with a diamagnetic atom of 171Yb and
performed projective measurements on a single nuclear spin. Since Yb has no
electronic spin and has 1/2 nuclear spin, the procedure of spin polarization
and state verification can be dramatically simplified compared with the pseudo
spin-1/2 system. By enhancing the photon emission rate of the 1S0-3P1
transition, projective measurement is implemented for an atom with the
measurement time of T_meas = 30us. Unwanted spin flip as well as dark counts of
the detector lead to systematic error when the present technique is applied for
the determination of diagonal elements of an unknown spin state, which is
delta|beta|^2 < 2 * 10^-2. Fast measurement on a long-lived qubit is key to the
realization of large-scale one-way quantum computing.Comment: 5 pages, 5 figure
Total Synthesis and Structural Revision of Cyclotetrapeptide Asperterrestide A
The structural revision
of cyclotetrapeptide asperterrestide A
has been achieved based on total synthesis and molecular modeling.
For these studies, (2R,3S)-MePhe(3-OH)
and (2S,3S)-MePhe(3-OH) suitably
protected for peptide synthesis were prepared via a stereoselective
reduction of a ketone precursor derived from L- or d-serine,
using L-selectride or DIBAL-H. The synthesis of the proposed structure
of asperterrestide A (1a) was accomplished by solution-phase
synthesis of a linear precursor followed by macrolactamization. The
NMR spectra of our synthetic 1a were not identical to
those reported for the natural compound. Molecular modeling studies
suggested that the correct structure 1b was the one in
which the stereochemistry at the α-positions of the Ala and
MePhe(3-OH) residues is the opposite to that of the proposed structure.
This was confirmed by the total synthesis of 1b and its
subsequent structural characterization
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