Quantum computing advances with silicon-based donor spin qubits

Quantum computing advances with silicon-based donor spin qubits
by Robert Schreiber
Berlin, Germany (SPX) Jan 10, 2025
The EQUSPACE consortium, known as Enabling New Quantum Frontiers with Spin Acoustics in Silicon, has secured 3.2 million euros from the European Innovation Council's Pathfinder Open funding program. This initiative is focused on advancing silicon-based quantum technologies by bringing together expertise from spin qubits, optomechanics, and atomic silicon modifications. The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and four other partners from three EU countries are working collaboratively to develop a novel silicon quantum platform.

Silicon, the foundation of traditional computing, has not yet emerged as a dominant material for quantum computing. However, leveraging the extensive semiconductor infrastructure to process qubits could prove to be a significant step forward. Donor spin qubits, which utilize the spin properties of impurity atoms, offer potential due to their stability over extended periods, a critical requirement for quantum mechanical computations. Despite these advantages, the absence of scalable coupling and readout mechanisms has limited their commercial viability.

The EQUSPACE project aims to overcome these limitations by connecting donor spin qubits using sound waves in vibrating structures. The platform will incorporate lasers and single-electron transistors to enable electrical readout of computational results. Researchers plan to develop scalable solutions for controlling and reading results, establishing spin-spin coupling, and transmitting quantum information between qubits on the silicon chip. The ultimate goal is a comprehensive quantum information platform featuring qubits, interconnects, and scalable electronics.

HZDR's role in advancing silicon quantum technology

The Institute of Ion Beam Physics and Materials Research at HZDR is a key contributor to EQUSPACE, offering expertise in atomic modifications of silicon for quantum applications. Using a focused ion beam, the team will enrich ultra-pure silicon with the isotope silicon-28, which lacks atomic nuclei spin. This property minimizes interactions with magnetic fields or other particle spins, maintaining quantum state stability for longer durations.

"Through the targeted enrichment with special isotopes, the quantum state remains stable for longer timespans. This allows more complex quantum operations, and the platform could thus outperform classical computers and other quantum computer systems in the future," explained Dr. Nico Klingner, HZDR project manager.

Additionally, HZDR is developing single-ion implantation techniques for donor atoms, such as bismuth, to form two-state systems. At extremely low temperatures, these systems exhibit superposition, allowing simultaneous existence of "up" and "down" spin states. This unique property enables parallel quantum computations, greatly enhancing processing power. Donor spin qubits also exhibit relative stability compared to superconducting circuit-based qubits, maintaining coherence over longer periods and supporting scalability without sacrificing computation precision.

"These contributions from HZDR, especially in the areas of isotope purification, implantation and strain engineering in semiconductors, are fundamental to the success of the EQUSPACE project," stated Professor Juha Muhonen, project coordinator.

Boosting Europe's quantum leadership

The EQUSPACE consortium comprises researchers from the University of Jyvaskyla, VTT Technical Research Center of Finland, HZDR, NWO Institute AMOLF in the Netherlands, and Finnish start-up SemiQon Oy. This collaboration underscores Europe's commitment to competing globally in the quantum technology arena, where challenges from the USA, China, Canada, and Australia are intensifying.

"EQUSPACE's approach is crucial to ensure that Europe remains competitive in the rapidly advancing field of quantum technologies. With this funding, EQUSPACE is building a strong research network in Europe based on donor spin qubits - a development that will strengthen the European quantum industry in the long term," added Muhonen. The project, funded under Horizon Europe, is set to commence on February 1, 2025.