(a) Schematic of HHG in a mixed-gas jet composed of He and Ar. HHG occurs at each atom and the generated EUV radiation propagates to a far-field detector, where interference between the harmonic emissions from the different species becomes evident. (b) Single-atom HHG spectra for He (green) and Ar (blue), obtained by solving the 3D-TDSE for a driving pulse with 800 nm wavelength, 2.84 × 10¹⁴ W/cm² peak intensity, and 7.7 fs pulse duration.