Coherent control of orthogonal continuum states in XUV photoionization

Abstract

We demonstrate coherent control of orthogonal continuum electron states in the XUV photoionization of atomic hydrogen using polarization-tailored driving fields. By combining polarization mixing with carrier-envelope-phase (CEP) control, we generate a pair of orthogonal momentum-space basis states whose populations and relative phase can be independently tuned via the polarization-mixing parameter and CEP, respectively. The resulting photoelectron wave packets are prepared as coherent superpositions within this effective two-dimensional subspace, with quantum coherence confirmed by interference visibilities reaching 99% in the photoelectron momentum distributions (PMDs). We further demonstrate that a bichromatic driving-field configuration extends this framework to a four-dimensional continuum manifold, with basis states distinguished by both angular emission patterns and radial momentum distributions, and with independent amplitude and phase control preserved across the higher-dimensional subspace. These results establish that polarization-tailored XUV fields provide a flexible route to independent amplitude and phase control within low-dimensional subspaces of the photoelectron continuum, with the engineered dynamics directly observable in momentum-resolved spectra.