Quantum Tech

‘Near perfect’ control of single atoms major advance towards quantum computing

27th March 2024
Paige West

Engineers and physicists at UCL have developed a new fabrication process for building quantum computers, achieving an almost zero failure rate with the potential for scaling up.

This breakthrough marks the first reliable method for positioning single atoms within an array, a concept initially proposed 25 years ago. With near-perfect precision and scalability, this method opens the door to constructing a quantum computer capable of addressing the world's most intricate problems, albeit facing significant engineering hurdles ahead.

Quantum computing holds the promise of solving complex issues beyond the reach of traditional binary, transistor-based computers. This new approach involves creating qubits (quantum bits) from single atoms embedded in silicon and cooled to very low temperatures to maintain quantum stability. These atoms, manipulable through electrical and magnetic signals, facilitate information processing in a manner akin to binary transistors in classical computers.

Such quantum computing exploits the fundamental principles of quantum mechanics, including superposition – the capacity of qubits to assume multiple states simultaneously – and quantum entanglement, where qubits become inseparably interconnected. This capability enables quantum computers to explore numerous potential outcomes concurrently, a task that would take today's most advanced supercomputers millions of years.

Despite ongoing efforts, current quantum computing projects have not yet achieved the necessary scale and low error rates. A novel method by UCL researchers involves positioning 'impurity' atoms within a silicon crystal, utilising arsenic instead of phosphorus to leverage its inherently low qubit error rates and compatibility with scalable silicon microelectronics technologies. This technique has historically seen a 70% success rate with phosphorus, underscoring the need for a more reliable material like arsenic to attain the near-zero failure rates essential for quantum computing.

Dr Taylor Stock, first author of the study from UCL Electronic & Electrical Engineering, emphasised the challenges in reducing qubit error rates and scaling up the number of qubits in contemporary quantum computing systems. Through their research, they discovered that arsenic atoms could be positioned more reliably than phosphorus, achieving an estimated 97% accuracy rate, with aspirations to reach 100% soon.

Currently, the positioning of each atom is a manual, time-consuming process, suggesting the need for automation and industrialisation to create vast arrays of qubits necessary for a universal quantum computer. The silicon semiconductor industry, valued at around $550 billion and familiar with arsenic and silicon, is poised to play a pivotal role in advancing this field. The compatibility of the new approach with existing semiconductor processing offers hope for its integration once engineering obstacles are addressed.

Professor Neil Curson, senior author of the study from UCL Electronic & Electrical Engineering, highlighted the significance of achieving such precision and scalability in quantum computing. He sees this as a critical milestone, marking the first instance where the accuracy and scale required for quantum computing have been demonstrated, presenting a substantial engineering challenge to expedite and simplify the process. However, he expressed confidence in the feasibility of constructing a universal quantum computer.

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