Hi group,
Dr. Qi Wei from Professor Herschbach's lab will giving us a 30-40min talk
tomorrow *3/22/2011 at 1:30* in the division room. He'll talk about his
recent work with Prof Herschbach analyzing the use of molecules for quantum
computing. The abstract is below:
*Title: *Entanglement of polar molecules in pendular states
*Abstract: *In proposals for quantum computers using arrays of trapped
ultracold polar molecules as qubits, a strong external field with appreciable
gradient is imposed in order to prevent quenching of the dipole moments by
rotation and to distinguish among the qubit sites. That field induces the
molecular dipoles to undergo pendular oscillations, which markedly affect
the qubit states and the dipole-dipole interaction. We evaluate entanglement
of the pendular qubit states for two linear dipoles, characterized by
pairwise concurrence, as a function of the molecular dipole moment and
rotational constant, strengths of the external field and the dipole-dipole
coupling, and ambient temperature. We also evaluate a key frequency shift
produced by the dipole-dipole interaction. Under conditions envisioned for
the proposed quantum computers, both the concurrence and the key frequency
become very small for the ground eigenstate. In principle, such weak
entanglement can be sufficient for operation of logic gates, provided the
resolution is high enough to detect the frequency shift unambiguously. In
practice, however, for many candidate polar molecules it appears a
challenging task to attain adequate resolution. Simple approximate formulas
fitted to our numerical results are provided from which the concurrence and
frequency shift can be obtained in terms of unitless reduced variables.
J. D. Whitfield
Aspuru-Guzik Group
Department of Chemistry and Chemical Biology
Harvard University
tel: 301-520-7847
web:
aspuru.chem.harvard.edu/people/James_Whitfield