For the first time, scientists from the University of New South Wales (UNSW) Sydney have demonstrated that it is possible to build atomic precision qubits in a three-dimensional (3D) device.
The researchers claim they were able to extend their atomic qubit fabrication technique to different layers of a silicon crystal, which enabled them to create a vital component of the 3D chip architecture they had invented in 2015.
The research team was led by Michelle Simmons, Director of UNSW's Centre of Excellence for Quantum Computation and Communication Technology (CQC2T).
Data in classical computers is rendered as binary bits: 0 or 1. However, a quantum bit (qubit) can exist in both of these states at once. A qubit operation allows many computations to be performed in parallel, meaning quantum computers can far exceed the most powerful super computers of present time.
In 2015, the UNSW research team, in collaboration with another group of researchers from the University of Melbourne, had announced designing a 3D silicon chip architecture based on single atom quantum bits.
This new 3D chip architecture was said to provide a blueprint to create a large-scale quantum computer. The new silicon architecture uses atomic-scale qubits, aligned to control lines (essentially very narrow wires), inside a 3D design. The qubit layer in this 3D architecture is "sandwiched" between two layers of wires, which are arranged in a grid.
In their latest paper, researchers state that they have got success in aligning different layers in the 3D device with nanometre precision and were also able to read out qubit states with high fidelity within one single measurement.
"This 3D device architecture is a significant advancement for atomic qubits in silicon," said Professor Simmons.
"To be able to constantly correct for errors in quantum calculations - an important milestone in our field - you have to be able to control many qubits in parallel."
According to researchers, building a second control layer on the top of the first layer of quibts is very complicated process. They first created the first layer, and then grew the second layer by optimizing a technique, without disturbing the structures in the first layer.
The team also demonstrated that these multiple layers can be aligned with nanometre precision.
The team is now working to develop a large-scale architecture to enable commercialisation of their technology.
The findings of the study are published in journal Nature Nanotechnology.
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