Faster Simulations of Quantum Dots
Quantum dots (QDs) are being investigated as one possible component of ultra-fast computers. The electron spins within these structures can serve as qubits. QDs can also be a source of entangled photons. By entangling the qubits, a processor would be able to take advantage of the parallelism inherent to quantum mechanics. Specific software algorithms could show a significant speed up when run on a machine using these fundamental units. The pyramidal dots themselves can be 100 nanometers high with only 200 atoms for each side. Trying to model molecules quantum mechanically is computationally intensive. Ironically, one of the benefits of quantum computers is being able to simulate molecular processes with greater speed and fidelity. A quantum simulator would be an analog device that could model the intricate details of atomic interactions in a way a digital CPU could not. This may lead to more breakthroughs in chemistry and material science. Currently, though, the amount of entangled qubits is low and this number would have to be increased to hundreds before these specialized computers could become viable in this arena. To help scientists reach that point, they have to be able to emulate QD’s on conventional machines. Any shortcut they find to do this is enormously helpful in expediting the analysis and new work has uncovered a superior method of accomplishing this.
Researchers at EPFL’s Laboratory of Physics and Nanostructures wanted to understand the optical properties of QDs. The QDs can emit photons and this capability makes them a possible cheaper future light source or supercomputing component. They can also be utilized as solar panel material. There are other possible uses as well. The scientists have developed a novel physical theory that can reduce the amount of time needed to carry out the calculations. The main scientist Marc-André Dupertuis figured out that the behavior of QD’s could be better understood by taking into account the symmetries of the wave function. The wave function describes the quirky properties of matter on an atomic scale. These electron states oscillate when electrical current is injected into the QD. The amount of equations necessary to describe the object can be significantly reduced by using a mathematical tool known as group theory. Efficiently modeling the quantum dots could lead to novel nanotechnologies in the future. The theoretical approach analyzes the true degeneracies and polarized decay patterns of exciton complexes that exist within semiconductor quantum dots. Excitons are a bound state of an electron coupled with an electron hole. The scientists found a high agreement of the models with spectroscopy characterizations. It is not an easy task to be able to simplify the description of the particle’s behavior while retaining a high degree of accuracy. However, this avenue appears to have performed the task well.
The paper is about “Symmetries and the polarized optical spectra of exciton complexes in quantum dots“.
See the article good vibrations for future quantum computers for more information.
