  Ultracold atoms are a powerful resource for quantum technologies. As such,
they are usually confined in an external potential that often depends on the
atomic spin, which may lead to inhomogeneous broadening, phase separation and
decoherence. Dynamical decoupling provides an approach to mitigate these
effects by applying an external field that induces rapid spin rotations.
However, a continuous periodic driving of a generic interacting many-body
system eventually heats it up. The question is whether dynamical decoupling can
be applied at intermediate times without altering the underlying physics. Here
we answer this question affirmatively for a strongly interacting degenerate
Fermi gas held in a flat box-like potential. We counteract most of the
gravitational force by applying an external magnetic field with an appropriate
gradient. Since the magnetic force, and consequently, the whole potential, is
spin-dependent, we employ rf to induce a rapid spin rotation. The driving
causes atoms in both spin states to experience the same time-average flat
potential, leading to a uniform cloud. Most importantly, we find that when the
driving frequency is high enough, there is no heating on experimentally
relevant timescales, and physical observables are similar to those of a
stationary gas. In particular, we measure the pair-condensation fraction of a
fermionic superfluid at unitarity and the contact parameter in the BEC-BCS
crossover. The condensate fraction exhibits a non-monotonic dependence on the
drive frequency and reaches a value higher than its value without driving. The
contact agrees with recent theories and calculations for a uniform stationary
gas. Our results establish that a strongly-interacting quantum gas can be
dynamically decoupled from a spin-dependent potential for long periods of time
without modifying its intrinsic many-body behavior.
