  Following the first demonstration of a levitated nanosphere cooled to the
quantum ground state in 2020 [1], macroscopic quantum sensors are seemingly on
the horizon. The nanosphere's large mass as compared to other quantum systems
enhances the susceptibility of the nanoparticle to gravitational and inertial
forces. In this viewpoint we describe the features of experiments with
optically levitated nanoparticles [2] and their proposed utility for
acceleration sensing. Unique to the levitated nanoparticle platform is the
ability to implement not only quantum noise limited transduction, predicted by
quantum metrology to reach sensitivities on the order of $10^{-15}$ms$^{-2}$
[3], but also long-lived quantum spatial superpositions for enhanced
gravimetry. This follows a global trend in developing sensors, such as
cold-atom interferometers, that exploit superposition or entanglement. Thanks
to significant commercial development of these existing quantum technologies,
we discuss the feasibility of translating levitated nanoparticle research into
applications.
