  Nanofabricated mechanical resonators are gaining significant momentum among
potential quantum technologies due to their unique design freedom and
independence from naturally occurring resonances. With their functionality
being widely detached from material choice, they constitute ideal tools to be
used as transducers, i.e. intermediaries between different quantum systems, and
as memory elements in conjunction with quantum communication and computing
devices. Their capability to host ultra-long lived phonon modes is
particularity attractive for non-classical information storage, both for future
quantum technologies as well as for fundamental tests of physics. Here we
demonstrate such a mechanical quantum memory with an energy decay time of
$T_1\approx2$ ms, which is controlled through an optical interface engineered
to natively operate at telecom wavelengths. We further investigate the
coherence of the memory, equivalent to the dephasing $T_2^*$ for qubits, which
exhibits a power dependent value between 15 and 112 $\mu$s. This demonstration
is enabled by a novel optical scheme to create a superposition state of
$\rvert{0}\rangle+\rvert{1}\rangle$ mechanical excitations, with an arbitrary
ratio between the vacuum and single phonon components.
