The science behind Rydbergator
The basic physics of Rydbergator
Rydberg atoms are atoms with highly excited electrons (usually just one of them). The electron in a Rydberg state with high principal quantum number n orbits the nucleus at a large distance, where the Bohr model of an atom becomes a good approximation.
The electronic states of an atom are generally quantized and require a very specific amount of energy to be excited. The quantum of energy carried by light particles (photons) is determined by the color or more specifically, the wavelength of the light. Therefore only photons with the right wavelength (resonant photons) can be efficiently absorbed by the atoms making their electrons excited.
The excitation energy of an atom depends on the forces inside the atom and on externally applied electromagnetic fields.
Since the electron of a Rydberg atom is far away from its ionic core, it creates a strong dipolar field around it and can thereby influence the resonant energy of the surrounding atoms. Depending on the strength and sign of the interaction, this can either block or facilitate excitation of these atoms when the next laser light pulse is applied. In the case of facilitation, only atoms at a specific distance from an already excited Rydberg atom (where the resonance condition is satisfied) can get excited. This resonant excitation radius can be precisely controlled by the choice of the laser light wavelength.
The Germinate game simulates excitation of atoms into Rydberg states in a 2-dimensional plane. The atoms are placed on a hexagonal grid. Only atoms at the right distance from the already excited atoms can get excited (shown as raised blue hexagons in the figure). Too close or too far, the electron energy level is either too high (light blue) or too low (grey color hexagons) for the laser frequency. The excitation occurs in turns, in analogy with a sequential application of laser pulses in a real experiment.
The excitation mechanics in the real experiment occurs with a finite probability, depending on the power of the laser and the excited atoms may decay back to the ground state. In the game, the player is allowed to vary all laser and atomic parameters, and explore both physical and unphysical regimes, e..g, simplified excitation rules that allow excitation of all particles with certainty if their frequency is right.
The scientific purpose of the game is to provide a graphical tool for simulation of different excitation scenarios and to visualize the possible interesting dynamics in the field of Rydberg atoms.
To turn the physical simulator into a game, two species of Rydberg excitations (blue and yellow) can be excited by different laser frequencies. This allows the players to control and compare the excitation patterns formed and to compete, e.g., to conquer the largest group of excited atoms of a specific color.