The Silicon Vacancy in Silicon Carbide: a promising qubit in a technological material

点击翻译按钮获取中文摘要

How small can one shrink an electronic memory? The ultimate limit in storage can be reached by encoding information in a single particle, for example a single electron or a single atomic nucleus. There are several ways to encode a bit of information into an electron. For example, one could label "1" the presence of the particle, and "0" its absence. Or, one could use an intrinsic property of quantum objects called "spin", which makes the particle behave as a tiny magnet. In this case, "1" would be encoded, for example, as spin pointing to the North Pole and "0" as spin pointing to the South Pole of the single particle magnet. Using single particles to encode information can give advantages that go beyond miniaturization. Electron spins obeys the laws of quantum mechanics. In quantum physics, the spin of an electron is not required to point either "North" or "South", like a magnetic needle, but it can be "North" AND "South" at the same time. Or, while a bit in a computing device is either in the "0" or "1" state, a quantum bit can be both at the same time. This is much more than a bizarre curiosity: in the last few decades, we have learnt that the laws of quantum mechanics can be exploited to perform tasks impossible for classical physics, such as secure communication, faster computing or precise sensing.The goal of this project is to measure and control single spins in silicon carbide, a material consisting of a lattice of silicon and carbon atoms. A silicon atom missing in this lattice creates a defect which hosts a single electronic spin that can be measured and manipulated by laser and radiofrequency pulses. Basically, this system behaves as a single atom trapped in silicon carbide. Why silicon carbide? In addition to hosting spins with great properties, silicon carbide is a technological material routinely used by the semiconductor industry to manufacture transistors and other microelectronic components. The availability of established recipes for growth, doping and nano-fabrication can lead to practical quantum devices.Control of single spins in silicon carbide is still in its infancy. We learned only recently how electrons are arranged in these defects. Only in the past year, control of a single spin in silicon carbide was demonstrated. There is plenty of information missing, and we can improve the efficiency of our control tools by learning more about the structure of these defects.This project will characterize the electronic structure of these defects by studying how they absorb and emit light. By operating at very low temperatures, the noise related to atomic vibrations which would mask the optical signal will be frozen out. The knowledge about light emission and absorption, and its relation to the spin trapped in the defect, will enable us to realizing exciting schemes that use single spins to encode and decode information for future technologies.