QScaleUp: Energy-efficient operation for scaling up quantum computing

José Carlos García-Abadillo Uriel obtained a degree in Physics in 2012 and a Master’s in Fundamental Physics in 2013 at the Universidad Complutense de Madrid (UCM). In 2014 he joined the Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC) where he worked on quantum computing using dopants and valley physics in nanostructures, receiving his Ph.D. “cum laude” from the Universidad Autónoma de Madrid (UAM) in 2018.

Between 2018 and 2023, he completed two postdoctoral stays at the University of Wisconsin-Madison (USA) and CEA in Grenoble (France), in which he worked on qubit dynamics, couplings between semiconductor qubits and QED cavities, as well as physics of holes in semiconductors. In this period, he provided theoretical support to several experiments carried out in these centres leading to publications in Nature Nano., Nature Phys. or Phys. Rev. Lett.

In April 2023, he returned to ICMM after becoming a ComFuturo fellow with his project QScaleUp.

La computación cuántica tiene enormes posibilidades para impactar en distintas áreas como la química o la ciberseguridad. Sin embargo, el potencial real de los ordenadores cuánticos solo se alcanzará cuando se pueda escalar eficientemente el número de cúbits que usan, que son la unidad fundamental de información de estos ordenadores. Un ordenador cuántico a gran escala requeriría miles de estas unidades que a su vez necesitarían para funcionar grandes cantidades de energía, motivo por el cual es esencial encontrar plataformas y métodos óptimos de escalado. El proyecto QScaleUp se centra en investigar un tipo concreto de plataforma de procesadores cuánticos, la basada en la manipulación de cúbits de espín en semiconductores, que reduce significativamente los requisitos de energía para la manipulación y, potencialmente, la refrigeración. Esto le confiere claras ventajas como plataforma escalable y energéticamente eficiente en el desarrollo de ordenadores cuánticos potentes y sostenibles.
Quantum computing has enormous potential to impact areas such as chemistry and cybersecurity. However, the real potential of quantum computers will only be achieved when the number of cubits they use, which are the fundamental unit of information in quantum computers, can be scaled up efficiently. A large-scale quantum computer would require thousands of these units, which in turn would require large amounts of energy to operate, which is why it is essential to find optimal scaling platforms and methods. The QScaleUp project focuses on investigating a particular type of quantum processor platform, one based on the manipulation of spin cubits in semiconductors, which significantly reduces the power requirements for manipulation and, potentially, cooling. This gives it clear advantages as a scalable and energy-efficient platform in the development of powerful and sustainable quantum computers.

Extended project summary:

At the beginning of the XX century, the foundations of physics were shaken by the emergence of quantum mechanics. Forty years later, the first quantum revolution was born with the invention of the transistor. In 1986, it was theorized that one could use the properties of quantum mechanics to build a computer. Such a computer would allow solving problems beyond classical computers’ reach. As of today, there is no doubt that quantum advantage has the potential to revolutionize multiple fields: cryptography, database search, drug development, or dark matter search, among others.

Due to increased interest in this area, the most important technology companies have started funding their quantum technologies programs with successful demonstrations of tens of qubits. However, there is still a long way to go before the real potential of quantum computing can be fully achieved. Scaling up to a large number of qubits is a considerable challenge. By adding qubits, the power requirements for manipulation and refrigeration further increase. Sustainably taking quantum computers to the desired scales will require new ideas and further optimization.

The QScaleUp project is based in the belief that spin qubits in semiconductors could provide a platform for an efficient quantum computer. Semiconductor-based qubits stand out compared to other platforms due to their potential for scalability. A single wafer can host tens of thousands of qubits, and high-temperature operation (>1K) has been demonstrated, strongly reducing the refrigeration power requirements and allowing integration with the classical control on the same stage. This advantage will give an edge to this technology over others in the long run.

The main goal of this project is to theoretically develop and optimize energy-efficient ways of manipulating semiconductor qubits and their interactions. For achieving this goal, the project will focus mainly on hole spin qubits which have shown great potential for low-power manipulation.