Silicon Photonics for Quantum Computing

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The most ambitious application for silicon photonics - Chrostowski's expertise - is in quantum computing. Quantum computing is expected to deliver the next leap in information technology, with anticipated impacts as significant as the development of silicon integrated circuits and the Internet. Quantum computing (QC) differs from classical computing in that particles (electrons, photons) that store bits of information (a quantum bit or "qubit") can exist as a linear combination of states (called superposition), whereas a classical bit can only be in one state. Superposition, together with correlations between qubits (entanglement), offer quantum computers (QCs) an exponential advantage over classical computers, where even 100 qubit QCs would outperform supercomputers with trillions of classical transistors. This would allow us to solve some of the world's most pressing computational and societal problems that are unsolvable by classical computers. QC will enable breakthroughs in fields as diverse as chemical design (e.g. enzymes for carbon capture), material design (e.g. batteries), precision health, optimization, and artificial intelligence. There are several hardware approaches being pursued in industry: the leading contenders are based on superconducting (IBM, Google) and trapped ion (IonQ, Honeywell) qubits. New contenders are based on spins in silicon (Intel) and photonics (PsiQuantum, Xanadu). These silicon-based approaches offer the potential for scaling to millions of qubits owing to the small device size and wafer-scale manufacturing. There are now two prominent silicon photonics QC start-ups, PsiQuantum in California, and Xanadu in Toronto, which have raised $509M and $36M, respectively. This proposal aims to develop a new architecture that has the potential to solve the challenges faced by the above approaches. We propose to develop a silicon-based platform that uses implanted donors as electron spin qubits with photonics used for the interconnects. This hybrid electro-optic approach makes use of two key advantages - electrons make excellent memories (qubits), while photons are excellent for communication (entanglement). This research program will fund 4 PhD, 3 MASc and 8 undergraduate students to design, fabricate, and test photonic devices for quantum computing using silicon donor spin qubits, with the long-term goal of developing all ingredients necessary to build a scalable fault-tolerant QC. Trainees will build experimental apparatus for testing at cryogenic temperatures, design novel nano-photonic components for quantum information processing (single photon sources and detectors, spin qubit to photon coupling using resonators, low-loss optical switches), develop novel fabrication techniques using infrastructure from a recent CFI Innovation grant, and demonstrate qubit operation in a scalable architecture. The HQP trained will be in a position to translate the research and technology into new commercial enterprises.