Shortcuts to adiabaticity for loading an ultracold Fermi gas into higher orbital bands of one-dimensional optical lattice

We present a shortcuts-to-adiabaticity protocol to load a spin-polarized ultracold Fermi gas from the ground ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mi>s</a:mi> </a:math> ) band into the first excited ( <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mi>p</b:mi> </b:math> ) band of a one-dimensional optical lattice. In contrast to a Bose-Einstein condensate in a shallow lattice—whose narrow quasimomentum distribution admits uniform lattice modulation—a noninteracting Fermi gas occupies the entire first Brillouin zone, rendering high-efficiency transfer across all momentum classes exceptionally challenging. To address this, we cast the loading process as a global, multiparameter optimization problem: We jointly optimize the timing of lattice-depth pulses and the corresponding phase shifts to maximize the ensemble-averaged transfer fidelity over all quasimomentum states. We demonstrate that fine phase tuning dramatically enhances loading efficiency, though the mean fidelity systematically decreases as more quasimomentum modes are occupied. Finally, we benchmark our shortcuts-to-adiabaticity protocol against established high-band-loading methods, underscoring its minimal hardware requirements and submillisecond timescales. Our work provides a practical path for rapid, high-fidelity preparation of Fermi gases in excited lattice orbitals, opening avenues for exploring orbital dynamics, anisotropic interactions, and many-body phenomena.