  We extend two rigorous results of Aizenman, Lebowitz, and Ruelle in their
pioneering paper of 1987 on the Sherrington-Kirkpatrick spin-glass model
without external magnetic field to the quantum case with a "transverse field"
of strength $b$. More precisely, if the Gaussian disorder is weak in the sense
that its standard deviation $v>0$ is smaller than the temperature $1/\beta$,
then the (random) free energy almost surely equals the annealed free energy in
the macroscopic limit and there is no spin-glass phase for any $b/v\geq0$. The
macroscopic annealed free energy (times $\beta$) turns out to be non-trivial
and given, for any $\beta v>0$, by the global minimum of a certain functional
of square-integrable functions on the unit square according to a Varadhan
large-deviation principle. For $\beta v<1$ we determine this minimum up to the
order $(\beta v)^4$ with the Taylor coefficients explicitly given as functions
of $\beta b$ and with a remainder not exceeding $(\beta v)^6/16$. As a
by-product we prove that the so-called static approximation to the minimization
problem yields the wrong $\beta b$-dependence even to lowest order. Our main
tool for dealing with the non-commutativity of the spin-operator components is
a probabilistic representation of the Boltzmann-Gibbs operator by a Feynman-Kac
(path-integral) formula based on an independent collection of Poisson processes
in the positive half-line with common rate $\beta b$. Its essence dates back to
Kac in 1956, but the formula was published only in 1989 by Gaveau and Schulman.
