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Means Found to Prevent Information Loss of Qubit in Semiconductor


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Some day we may see quantum computers running algorithms and models no modern computer could hope to complete, but there is still a lot to do before that day comes. Part of that work is figuring out how to protect the quantum information because the states that store it are very fragile. Researchers at the Technical University of Munich, Los Alamos National Laboratory, and Stanford University however have found a way to protect qubits held between two semiconductor materials.

Qubits are analogous to the electronic bits in modern devices, but store information using quantum states, like spin, and superposition, which is a phenomenon allowing one particle to be in multiple states at the same time. The qubits the researchers were working with were made by putting a layer of indium gallium arsenide on a gallium arsenide substrate. These two materials have different structures, which puts strain on the interface between them, resulting in quantum dots. By cooling the system and optically exciting it, single electrons can be trapped in each dot, and then the spins of these electrons can store the quantum information. When they did this though, the researchers found that the qubits would lose their information after a few hundred nanoseconds because of tiny electric fields that formed and affected the spins of the atomic nuclei around the electrons.

This discovery led the researchers to find other ways information could be lost, but they also found the loss could be avoided by applying a magnetic field to the system, about the strength of a strong permanent magnet. The field acts to stabilize the nuclear spins and thus protects the electron spins. Because the qubits are stored within semiconductor quantum dots, they have potential for being integrated into current computer technology, and could even have electrical contacts applied, so voltages instead of light pulses could be used to manipulate them.

Source: Technical University of Munich

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