How do you determine what is going on when you can’t actually see the components in the system you are investigating? This is the challenge when investigating the quantum behavior of electrons in a lattice of ions. The solution being created by the Physics Department at the University of San Diego, California is to build a model that is slightly larger with observable components of atoms moving in an optical lattice. The challenge is to cool the atoms to near absolute zero and then move them into a triangular lattice formation using pulses of laser light, which have to be ultra-precise, with virtually no noise in the control signal for the laser beams. To achieve this, a Spectrum Instrumentation M4i.6622-x8 Arbitrary Waveform Generator is used.
Dr. Julio Barreiro, the Assistant Professor in charge of the research, explained: “To manipulate individual atoms, you need extraordinary precision to deliver exactly the right amount of energy from each laser pulse. I heard about the precision of Spectrum AWGs from a colleague at CalTech who is using one to move individual atoms in his research and recommended them. Its extreme precision and lack of noise is exactly what we need, otherwise atoms would not go where we want them and, worse, any signal noise would heat up the atoms.”
The first step is to cool a few million strontium atoms to within a few hundred nano-degrees of absolute zero in a vacuum chamber. The next step is to move the ultra-cold atoms into a flat sheet like a pancake again using laser pulses. Then, three lasers that are arranged in a plane at 120 degrees from each other, are fired in turn to propel the atoms into synchronized triangle patterns. These dancing atoms are simulating the quantum behavior of electrons in a lattice of ions. “This gives us a model of quantum behavior that we can observe with ultra-sensitive cameras as we subject it to changing conditions to see how our predicted result from computer modelling compares with reality,” added Dr. Barreiro, “which is something that you just cannot do at the electron level.” For a size comparison, this modeling is working at 500nm sizes, whereas the electrons in a lattice is at the level of Angstroms. The precise and coordinated dance of the atoms in a triangular lattice is enabled by multiple triplets of laser light frequencies controlled by the Spectrum AWG using its multi-channel outputs.