  The effective control of atomic coherence with cold atoms has made atom
interferometry an essential tool for quantum sensors and precision
measurements. The performance of these interferometers is closely related to
the operation of large wave packet separations. We present here a novel
approach for atomic beam splitters based on the stroboscopic stabilization of
quantum states in an accelerated optical lattice. The corresponding Floquet
state is generated by optimal control protocols. In this way, we demonstrate an
unprecedented Large Momentum Transfer (LMT) interferometer, with a momentum
separation of 600 photon recoils ($600\hbar k$) between its two arms. Each LMT
beam splitter is realized in a remarkably short time (2 ms) and is highly
robust against the initial velocity dispersion of the wave packet and lattice
depth fluctuations. Our study shows that Floquet engineering is a promising
tool for exploring new frontiers in quantum physics at large scales, with
applications in quantum sensing and testing fundamental physics.
