Abstract Quantum computation (QC) is one of the most challenging quantum technologies that promise to revolutionize data computation in the long-term by outperforming the classical supercomputers in specific applications. Errors will hamper this quantum revolution if not sufficiently limited and corrected by quantum error correction codes thus avoiding quantum algorithm failures. In particular millions of highly-coherent qubits arranged in a two-dimensional array are required to implement the surface code, one of the most promising codes for quantum error correction. One of the most attractive technologies to fabricate such large number of almost identical high-quality devices is the well known metal-oxide-semiconductor technology. Silicon quantum processor manufacturing can leverage the technological developments achieved in the last 50 years in the semiconductor industry. Here, we review modeling, fabrication aspects and experimental figures of merit of qubits defined in the spin degree of freedom of charge carriers confined in quantum dots and donors in silicon devices along with classical electronics innovations for qubit control and readout. Furthermore, we discuss potential applications of the technology and finally we review the role of start-ups and companies in the silicon-based QC era.
Abstract Quantum computation (QC) is one of the most challenging quantum technologies that promise to revolutionize data computation in the long-term by outperforming the classical supercomputers in specific applications. Errors will hamper this quantum revolution if not sufficiently limited and corrected by quantum error correction codes thus avoiding quantum algorithm failures. In particular millions of highly-coherent qubits arranged in a two-dimensional array are required to implement the surface code, one of the most promising codes for quantum error correction. One of the most attractive technologies to fabricate such large number of almost identical high-quality devices is the well known metal-oxide-semiconductor technology. Silicon quantum processor manufacturing can leverage the technological developments achieved in the last 50 years in the semiconductor industry. Here, we review modeling, fabrication aspects and experimental figures of merit of qubits defined in the spin degree of freedom of charge carriers confined in quantum dots and donors in silicon devices along with classical electronics innovations for qubit control and readout. Furthermore, we discuss potential applications of the technology and finally we review the role of start-ups and companies in the silicon-based QC era.
Abstract Recent advances in quantum error correction codes for fault-tolerant quantum computing and physical realizations of high-fidelity qubits in multiple platforms give promise for the construction of a quantum computer based on millions of interacting qubits. However, the classical-quantum interface remains a nascent field of exploration. Here, we propose an architecture for a silicon-based quantum computer processor based on complementary metal-oxide-semiconductor (CMOS) technology. We show how a transistor-based control circuit together with charge-storage electrodes can be used to operate a dense and scalable two-dimensional qubit system. The qubits are defined by the spin state of a single electron confined in quantum dots, coupled via exchange interactions, controlled using a microwave cavity, and measured via gate-based dispersive readout. We implement a spin qubit surface code, showing the prospects for universal quantum computation. We discuss the challenges and focus areas that need to be addressed, providing a path for large-scale quantum computing.
Recent advances in quantum error correction codes for fault-tolerant quantum computing and physical realizations of high-fidelity qubits in multiple platforms give promise for the construction of a quantum computer based on millions of interacting qubits. However, the classical-quantum interface remains a nascent field of exploration. Here, we propose an architecture for a silicon-based quantum computer processor based on complementary metal-oxide-semiconductor (CMOS) technology. We show how a transistor-based control circuit together with charge-storage electrodes can be used to operate a dense and scalable two-dimensional qubit system. The qubits are defined by the spin state of a single electron confined in quantum dots, coupled via exchange interactions, controlled using a microwave cavity, and measured via gate-based dispersive readout. We implement a spin qubit surface code, showing the prospects for universal quantum computation. We discuss the challenges and focus areas that need to be addressed, providing a path for large-scale quantum computing.
As quantum processors grow in complexity, the focus is shifting towards the scaling of the entire quantum computing system, including the quantum hardware but as well the classical support electronics. Silicon-based quantum computing offers the enticing possibility that the quantum processor, the quantum-classical interface, and the classical layer can all, in principle, be manufactured using complementary metal-oxide semiconductor (CMOS) technology, creating an opportunity to move from distributed quantum-classical systems to integrated quantum computing solutions. Here, we review the state-of-the-art in spin-based quantum computing in silicon and present different approaches to help scale the technology using CMOS technology. We discuss the use of industry-manufactured silicon devices as the basic qubit element and present radio-frequency reflectometry techniques for fast high-fidelity spin readout. Finally, we show how quantum-classical co-integration can enable large-scale control and readout via frequency- and time-domain multiplexing.
The understanding of quantum mechanics enabled the development of technology such as transistors and has been the foundation of today’s information age. Actively using quantum mechanics to build quantum technology may cause a second revolution in handling information. However, to execute meaningful algorithms, largescale quantum computers have to be built. Such systems are constructed from many qubits, the quantum version of the classical bit. While exciting progress is being made across a range of different qubit platforms, achieving the radical scalability that is necessary to build a largescale processor could be a roadblock. Huge challenges are put on reproducibility, inand output connectivity and material quality. Qubits based on the spins of electrons and holes confined in semiconductor quantum dots may have an important advantage in constructing quantum processors. This platform can profit from the advanced semiconductor industry that was responsible for the first computing revolution. Group IV semiconductors such as silicon and germanium have a high compatibility with industrial semiconductor manufacturing and contain stable isotopes with zero nuclear spin. The materials can be isotopically purified and serve as excellent hosts for spins with long quantum coherence. In Chapter 3 we present quantum dot arrays in silicon metaloxidesemiconductor (SiMOS), strained silicon (Si/SiGe) and strained germanium (Ge/SiGe). A nearly identical integration scheme based on an overlapping gate structure can be used to define quantum dots in each platform. Each platform has its own opportunities, which are carefully assessed. By employing charge sensing we confirm that all quantum dots can be depleted to the singleelectron regime. We compare capacitive crosstalk and find it to be the smallest in SiMOS, relevant for the tuning of quantum dot arrays. Using this crossplatform integration, we can study qubits in each platform with minimal overhead. Long coherence times, excellent singlequbit gate fidelities and twoqubit logic have been demonstrated with SiMOS spin qubits, making it one of the leading platforms for quantum information processing. However, due to the high disorder at the Si/SiO2 interface compared to Ge/SiGe and Si/SiGe interface, quantum dots defined in SiMOS are small and achieving sufficient control over single electrons has been a long standing challenge. In Chapter 5 we show experiments on a double quantum dot that can be isolated from its reservoir. We demonstrate a tunable tunnel coupling between single electrons up to 13 GHz and tunable tunnel rates down to below 1 Hz. These results mark an important step towards the required degree of control over the location of and coupling between quantum dots, necessary for the operation of a large array.
Quantum computing is one of the grand challenges of the 21st century and promises to transform almost every industry. As quantum computing technology exits the academic research phase into manufacturing, the goal is not to build single, unique qubits, but millions of interconnected, identical qubits capable of performing fully error corrected, general purpose calculations. Photon-based qubits offer a path to such a general-purpose machine by leveraging the mature silicon photonics high-volume manufacturing ecosystem. Creating quantum devices from silicon photonics components requires patterning innovation to bring leading-edge nanolithography to near macroscopic scale, a unique challenge for an industry where the future relies on progressive device shrink.
Quantum computing is one of the grand challenges of the 21st century and promises to transform almost every industry. As quantum computing technology exits the academic research phase into manufacturing, the goal is not to build single, unique qubits, but millions of interconnected, identical qubits capable of performing fully error corrected, general purpose calculations. Photon-based qubits offer a path to such a general-purpose machine by leveraging the mature silicon photonics high-volume manufacturing ecosystem. Creating quantum devices from silicon photonics components requires patterning innovation to bring leading-edge nanolithography to near macroscopic scale, a unique challenge for an industry where the future relies on progressive device shrink.