Comparison of quantum and classical gates in the 2D case: I_p = 24.59 eV, ₂ = 0.07, ₃ = 0, I = 1.36 × 10¹⁴ W cm⁻², λ = 1600 nm

Figure 2. Comparison of quantum and classical gates in the 2D case: I_p = 24.59 eV, ₂ = 0.07, ₃ = 0, I = 1.36 × 10¹⁴ W cm⁻², λ = 1600 nm. (a) Two-colour delay (black dots) corresponding to the maximum of the quantum gate Q^{q}_1, two-colour delay (red curve) corresponding to the maximum of classical gate Q^{c}_1, two-colour delay ₀ (green curve) corresponding to zero of the vector potential of the control field at the moment of ionization t_i. (b) Contrast of modulation for the quantum gate, normalized to its maximum for each recombination time. (c) Contrast of modulation for the classical gate.

Abstract

High harmonic spectroscopy has the potential to combine attosecond temporal with sub-Angstrom spatial resolution of the early nuclear and multielectron dynamics in molecules. It involves strong-field ionization of the molecule by an infrared (IR) laser field followed by time-delayed recombination of the removed electron with the molecular ion. The time-delay is controlled on the attosecond time scale by the oscillation of the IR field and is mapped into the harmonic number, providing a movie of molecular dynamics between ionization and recombination. One of the challenges in the analysis of a high harmonic signal stems from the fact that the complex dynamics of both ionization and recombination with their multiple observables are entangled in the harmonic signal. Disentangling this information requires a multidimensional approach, capable of mapping ionization and recombination dynamics into different independent parameters. We suggest multidimensional high harmonic spectroscopy as a tool for characterizing ionization and recombination processes separately allowing for simultaneous detection of both the ionization delays and sub-cycle ionization rates. Our method extends the capability of the two-dimensional set-up suggested recently by Shafir et al on reconstructing ionization delays, while keeping the reconstruction procedure as simple as in the original proposal. The scheme is based on the optimization of the high harmonic signal in orthogonally polarized strong fundamental and relatively weak multicolour control fields.