Physicists at the University of Basel can show for the first time what a single electron looks like in an artificial atom. A newly developed method allows them to show the probability that an electron is present in a space. This allows for better control of electron spins, which could serve as the smallest unit of information in a future quantum computer. The experiments were published in Physical revision letters and the related theory in Physical revision B.
The spin of an electron is a promising candidate for use as the smallest information unit (qubit) of a quantum computer. Controlling and changing this turn or coupling it with other turns is a challenge in which numerous research groups from all over the world work. The stability of a single turn and the entanglement of several turns depends, among other things, on the geometry of the electrons, which previously had been impossible to determine experimentally.
Only possible in artificial atoms.
Team scientists led by professors Dominik Zumbühl and Daniel Loss of the Department of Physics and the Swiss Institute of Nanoscience at the University of Basel have developed a method by which they can spatially determine the geometry of electrons at quantum dots.
A quantum dot is a potential trap that allows you to confine free electrons in an area that is approximately 1000 times larger than a natural atom. Because trapped electrons behave similarly to electrons attached to an atom, quantum dots are also known as "artificial atoms."
The electron is maintained at the quantum point by electric fields. However, it moves within space and, with different probabilities corresponding to a wave function, it remains in certain locations within its confinement.
Load distribution throws light
Scientists use spectroscopic measurements to determine energy levels at the quantum point and study the behavior of these levels in magnetic fields of varying intensity and orientation. On the basis of its theoretical model, it is possible to determine the probability density of the electron and, therefore, its wave function with an accuracy in the sub-nanometer scale.
"In a nutshell, we can use this method to show how an electron looks for the first time," explains Las.
Better understanding and optimization.
The researchers, who work closely with colleagues in Japan, Slovakia and the US Thus, they obtain a better understanding of the correlation between the geometry of electrons and the spin of the electron, which should be stable for as long as possible and quickly exchangeable to use as a qubit.
"Not only can we map the shape and orientation of the electron, but also control the wave function according to the configuration of the applied electric fields, which gives us the opportunity to optimize turn control in a very specific way." says Zumbühl.
The spatial orientation of the electrons also plays a role in the entanglement of several turns. Similar to the union of two atoms to a molecule, the wave functions of two electrons must lie in a plane for successful entanglement.
With the help of the developed method, numerous previous studies can be better understood and the performance of the spin qubits can be further optimized in the future.
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