  This technical note supplies an affirmative answer to a question raised in a
recent pre-print [arXiv:0910.1879] in the context of a "matrix recovery"
problem. Assume one samples m Hermitian matrices X_1, ..., X_m with replacement
from a finite collection. The deviation of the sum X_1+...+X_m from its
expected value in terms of the operator norm can be estimated by an "operator
Chernoff-bound" due to Ahlswede and Winter. The question arose whether the
bounds obtained this way continue to hold if the matrices are sampled without
replacement. We remark that a positive answer is implied by a classical
argument by Hoeffding. Some consequences for the matrix recovery problem are
sketched.
