Recent research from QuTech demonstrates a significant advancement in quantum computing technology. Scientists have successfully used a single hole trapped in a germanium quantum dot as a functional qubit, marking a breakthrough in quantum bit development that relies solely on standard semiconductor manufacturing techniques.
Holes, which are essentially the absence of electrons in a semiconductor’s atomic lattice, possess favorable quantum properties that make them excellent candidates for quantum computing. Unlike electrons, which have traditionally been the focus of qubit research, holes can maintain their quantum state for sufficient periods to perform computations and can be manipulated using only electrical signals. This eliminates the need for additional control components, potentially simplifying the scaling process for quantum computers.
While these advantageous properties were theoretically predicted in 2005, the practical implementation of isolating a single hole for use as a qubit remained elusive until now. The research team, led by Menno Veldhorst at QuTech (a collaboration between TU Delft and TNO), achieved this milestone using germanium.
Interestingly, germanium was the material used in the very first transistor created in 1947, though silicon later became the dominant semiconductor in modern electronics. Two years ago, QuTech researcher Giordano Scappucci demonstrated that germanium structures could be built with the high quality required for quantum applications. Now, Veldhorst’s team has developed a germanium quantum dot—a semiconductor particle just nanometers in size — capable of trapping a single hole.
What makes this development particularly promising is that these germanium quantum dots are created using the same manufacturing techniques employed to produce billions of transistors on conventional computer chips. This compatibility with existing semiconductor fabrication methods suggests a clearer pathway to scaling up quantum computing systems.
This achievement builds on the team’s earlier success in realizing two-qubit logic with germanium, published in Nature earlier in the same year. The researchers are now working toward developing larger qubit arrays using holes in germanium, bringing scalable quantum computing systems closer to reality.
Reference: Nature Communications 10 July 2020, https://doi.org/10.1038/s41467-020-17211-7
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