Science & Technology, Australia (Commonwealth Union) – Researchers from the Universities of Melbourne and Manchester have devised a groundbreaking method for producing exceptionally pure silicon, marking a significant leap forward in the development of powerful quantum computers.
According to the researchers, this novel technique for engineering ultra-pure silicon renders it an ideal material for manufacturing quantum computers on a large scale and with remarkable precision.
Professor David Jamieson, one of the project’s co-supervisors at the University of Melbourne, explained that the innovation, detailed in a publication in Communications Materials, a Nature journal, involves utilizing qubits of phosphorous atoms embedded within crystals of pure, stable silicon. This advancement could potentially surmount a critical obstacle in quantum computing by extending the duration of quantum coherence, which is notoriously fragile.
Professor Jamieson remarked that fragility in quantum coherence leads to the rapid accumulation of computing errors. With the robust coherence offered by the new technique, quantum computers could tackle problems in mere hours or minutes that would otherwise require conventional, or ‘classical,’ computers – including supercomputers – centuries to solve.
Quantum bits, or qubits, which are the fundamental units of quantum computers, are extremely sensitive to even the slightest changes in their surroundings, such as variations in temperature. Despite being operated within highly stable refrigerators at temperatures approaching absolute zero (minus 273 degrees Celsius), existing quantum computers can uphold error-free coherence for mere fractions of a second.
Professor Richard Curry, co-supervisor at the University of Manchester, highlighted that the use of ultra-pure silicon enables the fabrication of high-performance qubit devices. This advancement is pivotal in the journey toward scalable quantum computing.
Professor Curry pointed out in essence, that they have successfully produced a crucial ‘building block’ necessary for the development of silicon-based quantum computers. This achievement represents a significant stride towards a technology that holds immense transformative potential for humanity.
“Electronic chips currently within an everyday computer consist of billions of transistors — these can also be used to create qubits for silicon-based quantum devices. The ability to create high quality silicon qubits has in part been limited to date by the purity of the silicon starting material used. The breakthrough purity we show here solves this problem.”
Lead author Ravi Acharya, a Cookson Scholar from the University of Manchester and the University of Melbourne, underscored the notable advantage of silicon chip quantum computing: it leverages the same foundational techniques employed in the manufacturing of contemporary computer chips.
Professor Jamieson emphasized that the latest silicon computer chips, boasting high levels of purification, serve as a stronghold for qubits, allowing them to maintain quantum coherence for extended periods. This advancement drastically minimizes the necessity for error correction during complex computations.
he elaborated that their approach paves the way for dependable quantum computers, promising revolutionary advancements across various sectors, such as artificial intelligence, secure data transmission, vaccine and pharmaceutical development, as well as optimization in energy consumption, logistics, and manufacturing.
Silicon, derived from commonplace beach sand, stands as the cornerstone of today’s information technology realm due to its abundant nature and adaptable semiconductor properties. It possesses the unique capability to function either as an electrical conductor or insulator, contingent upon the addition of specific chemical elements.
Professor Jamieson pointed out that while alternative materials are under scrutiny, they firmly assert that silicon remains the primary contender for quantum computer chips, essential for maintaining enduring coherence crucial for reliable quantum computations.
“The problem is that while naturally occurring silicon is mostly the desirable isotope silicon-28, there’s also about 4.5 percent silicon-29. Silicon-29 has an extra neutron in each atom’s nucleus that acts like a tiny rogue magnet, destroying quantum coherence and creating computing errors,” added Professor Jamieson.
“The great news is to purify silicon to this level, we can now use a standard machine – an ion implanter – that you would find in any semiconductor fabrication lab, tuned to a specific configuration that we designed,” explained Professor Jamieson.
The scientists aimed a precise, swift beam of pure silicon-28 onto a silicon chip, facilitating the gradual replacement of silicon-29 atoms with silicon-28. This process diminished the silicon-29 content from 4.5 percent to a mere two parts per million (0.0002 percent).
In prior studies conducted in collaboration with the ARC Centre of Excellence for Quantum Computation and Communication Technology, the University of Melbourne established and maintains the global benchmark for single-qubit coherence at 30 seconds, utilizing silicon of lesser purity. This duration provides ample time for executing intricate quantum computations devoid of errors.
