Optical lattice
An optical lattice is formed by the interference of counter-propagating laser beams, creating a spatially periodic intensity pattern.
The resulting periodic potential may trap neutral atoms via the Stark shift.
The resulting arrangement of trapped atoms resembles a crystal lattice[2] and can be used for quantum simulation.
The potential experienced by the atoms is related to the intensity of the laser used to generate the optical lattice.
The potential depth of the optical lattice can be tuned in real time by changing the power of the laser, which is normally controlled by an acousto-optic modulator (AOM).
The AOM is tuned to deflect a variable amount of the laser power into the optical lattice.
Active power stabilization of the lattice laser can be accomplished by feedback of a photodiode signal to the AOM.
Titanium-sapphire lasers, with their large tunable range, provide a possible platform for direct tuning of wavelength in optical lattice systems.
Continuous control of the periodicity of a one-dimensional optical lattice while maintaining trapped atoms in-situ was first demonstrated in 2005 using a single-axis servo-controlled galvanometer.
Keeping atoms (or other particles) trapped while changing the lattice periodicity remains to be tested more thoroughly experimentally.
Such accordion lattices are useful for controlling ultracold atoms in optical lattices, where small spacing is essential for quantum tunneling, and large spacing enables single-site manipulation and spatially resolved detection.
Site-resolved detection of the occupancy of lattice sites of both bosons and fermions within a high tunneling regime is regularly performed in quantum gas microscopes.
This induced dipole will then interact with the electric field, leading to an energy shift
("red-detuning"), the induced dipole will be in phase with the field and thus the resulting potential energy gradient will point in the direction of higher intensity.
By use of additional laser beams, two- or three-dimensional optical lattices may be constructed.
Likewise, three orthogonal optical standing waves can give rise to a 3D array of sites which may be approximated as tightly confining harmonic oscillator potentials.
[1] Once cooled and trapped in an optical lattice, the atoms can be manipulated or left to evolve.
Common manipulations involve the "shaking" of the optical lattice by varying the relative phase between the counterpropagating beams or by modulating the frequency of one of the counterpropagating beams, or amplitude modulation of the lattice.
, a characteristic pattern in a TOF image of an optical-lattice system is a series of peaks along the lattice axis at momenta
Combined with in-situ absorption images (taken with the lattice still on), this is enough to determine the phase space density of the trapped atoms, an important metric for diagnosing Bose–Einstein condensation (or more generally, the formation of quantum degenerate phases of matter).
Atoms in an optical lattice provide an ideal quantum system where all parameters are highly controllable and where simplified models of condensed-matter physics may be experimentally realized.
Quantum gas microscopy techniques applied to trapped atom optical-lattice systems can even provide single-site imaging resolution of their evolution.
This is particularly relevant to complicated Hamiltonians which are not easily solvable using theoretical or numerical techniques, such as those for strongly correlated systems.
[17] Besides trapping cold atoms, optical lattices have been widely used in creating gratings and photonic crystals.
