Silicon Spin Qubits for Large-Scale Quantum Computing EU Quantum Flagship Programmme

The European consortium QLSI was launched on 1^st September 2020 with the goal of scaling silicon quantum technologies. This four-year EU project, coordinated by CEA, will lay the foundation for the EU’s industrial-scale implementation of semiconductor quantum processors and position Europe as a global leader in quantum computing. The project will focus on demonstrating that spin qubits are the leading platform for scaling to very large numbers of quantum bits (qubits) the building blocks of quantum information processing.

The QLSI consortium features a dynamic team with a complementary skillset, bringing together experienced academics, Research and Technology Organisations, major international businesses, as well as European start-ups. Each member brings state-of-the-art expertise in their area required to address the challenges of building a scalable quantum computer.

The partners have already realized some key advances in the field of semiconductor spin qubits, for example the demonstration of an “Ultrafast Hole Spin Qubit with Gate-Tunable Spin-Orbit Switch” in a Ge/Si nanowire quantum dot at the Zumbühl Group, University of Basel. The QLSI consortium will take this to next level with the demonstration of a 16-qubit chip in silicon CMOS (complementary metal oxide semiconductor) technology at the end of the project. What makes silicon so attractive? Owing to their experience, the partners have already quantified promising single qubit performance: small size, high fidelity, fast read-out and manipulation. Working with silicon, the next step is to leverage the vast infrastructure of the global semiconductor industry.

Superposition and entanglement

While classical computers use information as bits that are either off or on, represented by ‘0’ or ‘1’, quantum systems utilize superposition and entanglement of particles, such as electrons or photons, or other quanta. In superposition, these qubits are at 0 and 1 states simultaneously. When qubits get entangled, a primary feature of quantum mechanics, a change in one of them causes the other to also change.

Harnessing these features will make it possible to use quantum effects to make major advances in computing, sensing and metrology, simulations, cryptography, and telecommunications. Society’s benefits from quantum computing ultimately will include ultra-precise sensors for use in medicine, quantum-based communications, and hacking-proof digital data. In the long term, quantum computing has the potential to solve computational problems that would take current supercomputers longer than the age of the universe. These systems will also be able to recognize patterns and train artificial intelligence systems.

High-stakes, global competition

“Europe is well-positioned to take the EU’s spin-qubit R&D to the next level, in what is a high-stakes competition among advanced technological countries,” said Maud Vinet, CEA-Leti’s quantum hardware programme manager, who will lead the four-year, €15 million project. “The QLSI project ramps up a dedicated effort across all leading European groups in the field of spin qubits to develop complete processor systems that eventually will reach the thousands of qubits expected as a first step to show the potential for universal, error-corrected quantum computing.”

Prof. Daniel Loss, University of Basel: “There is enormous potential for silicon spin qubits due to their small size, fast speed of operation, and compatibility with established silicon large scale processing, making it possible to scale up to large numbers of qubits as needed in quantum computing.”

QLSI will pursue four essential results:

• Fabrication and operation of 16-qubit quantum processors based on industry-compatible semiconductor technology
• Demonstration of high-fidelity single- and two-qubit gates, read-out and initialization with these devices in a lab environment
• Demonstration of a quantum computer prototype, with online open-access for the community, integrating such a high-quality quantum processor in a semi-industrial environment (up to eight qubits available online), and
• Documentation of the requirements to address important issue of scalability towards large systems >1,000 qubits.

The project is a recent addition to the EU’s ambitious Quantum Flagship programme. The overall goal is to consolidate and expand European scientific leadership and excellence in quantum computing, to kick-start a competitive European industry in quantum technologies and to make Europe a dynamic and attractive region for innovative research, business and investments in this field. A complementary project to this hardware-focused project focuses on software requirements for fabricating spin qubits. 

19 QLSI consortium members

• CEA (Commissariat à l’énergie atomique et aux énergies alternatives) & CEA-Leti, France
• Centre Nationale de la Recherche Scientifique (CNRS), France
• Fraunhofer institutes IPMS & IAF, Germany
• TU Delft, Netherlands
• Forschungszentrum Jülich GmbH, Germany
• IMEC, Belgium
• University of Copenhagen, Denmark
• Infineon Dresden GmbH, Germany
• TNO (Netherlands organization for applied scientific research), Netherlands
• University of Konstanz, Germany
• University of Basel, Switzerland
• University of Twente, Netherlands
• University College London, United Kingdom
• Hitachi Europe Ltd, United Kingdom
• IHP - Leibniz Association, Germany
• Bull SAS/Atos SE, France
• Quantum Motion Technologies Ltd, United Kingdom
• Soitec SA, France
• STMicrolectronics SA, France