Quantum control via a genetic algorithm of the field ionization pathway of a Rydberg electron

Abstract

Quantum control of the pathway along which a Rydberg electron field ionizes is experimentally and computationally demonstrated. Selective field ionization is typically done with a slowly rising electric field pulse. The (1/n * ) 4 scaling of the classical ionization threshold leads to a rough mapping between arrival time of the electron signal and principal quantum number of the Rydberg electron. This is complicated by the many avoided level crossings that the electron must traverse on the way to ionization, which in general leads to broadening of the time-resolved field ionization signal. In order to control the ionization pathway, thus directing the signal to the desired arrival time, a perturbing electric field produced by an arbitrary waveform generator is added to a slowly rising electric field. A genetic algorithm evolves the perturbing field in an effort to achieve the target time-resolved field ionization signal.

Soft X-ray Induced Production of Neutral Fragments in High-Rydberg States at the O 1s Ionization Threshold of the Water Molecule

“… 14 An electron that begins in a single state at low field will spread out over multiple states as it passes through avoided crossings until field ionization. 29 Feynman et al 14 and Gregoric et al 29 have performed quantum mechanical calculations for the spreading of the amplitude using hydrogen-like wave functions in the parabolic basis and compared them with the experimental results of Rb atoms in high-Rydberg states. The calculations show that the spreading of amplitude can become very complicated if there are several avoided crossings before field ionization.…”

Improving the state selectivity of field ionization with quantum control

“…Each gene is subjected to a 1% chance of mutating; if a gene mutates, it is reset to a random value. For a fuller description of our algorithm, see [27]. The performance of a GA is highly dependent on how the fitness score is calculated, since this determines which genetic material is passed down to future generations.…”

“…A modification to SFI was recently developed in which the electron is directed through the many Stark states it encounters on the way to ionization, thus controlling the shape of the time-resolved signal [27]. This is done by perturbing the electric field ramp with a continuous series of small fluctuations in the electric field.…”

Time Dependence of Few-Body Förster Interactions among Ultracold Rydberg Atoms

“…Simulation suggests a Rydberg density on the order of 10 8 cm −3 , corresponding to an average spacing of about 20 μm. Highly excited atoms then exchange energy through a dipole-dipole interaction and the fraction of atoms in each state is quantified using directed field ionization (DFI) [34].…”

“…In addition, the p-state signal causes ringing in our detector, which makes quantitative measurement of the s 0 -state fraction difficult. We therefore use DFI to better resolve the s and p states and measure the s-state fraction [34][35][36]. Using a genetic algorithm, DFI optimizes a small perturbation that is added to an SFI ramp.…”