Dopant-Based Scalable Platform in Silicon for Quantum Information Processing

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Following the digital revolution, everyone is now massively using silicon transistors provided by microelectronics industry: They are the basic element not only of supercomputers, but of all electronic devices that have invaded every aspect of our modern lives (cell phones, PCs, GPS, cars, TV, internet router, .). This revolution of our modern society has brought increased comfort and allowed progress in science. Improvement of computer chips has been driven by reducing the size of the transistors, but this scaling has now reached a limit where both sensitivity to the exact position of single dopant atoms and quantum effects present major obstacles to further downscaling, calling for the exploration of highly innovative and disruptive approaches to further the development of computing in silicon. Several academic and major industrial players (as Intel) explore ultrascaled transistors at low temperature for quantum computation: The transistor channel then behaves as a quantum dot confining a single electron whose spin (instead of charge) is used to encode quantum information. Yet, the electron spin-coherence time is limited, allowing only for a very limited number of operations before the system decoheres, and the devices are still prone to dopant variability, preventing scalable architecture to emerge. In this discovery grant (DG) we instead consider nuclear spins of dopants, naturally present in transistors, to encode the quantum information. They have already demonstrated record coherence times, several orders of magnitude larger than the ones of electron spins in quantum dots. We will first address the key challenge for operating nuclear spin qubits: addressability. This DG will turn the strong sensitivity of ultrascaled transistor to individual dopants into an advantage. The small size of ultrascaled transistors will here be a key advantage by providing a means to focus electric and magnetic fields onto the well isolated nuclear spin. We will focus our research on dopants with high nuclear spin which provide the necessary redundancy to encode error-corrected logical qubits and allow for electrical manipulation of the spin, an essential asset to scalability. We will then develop coupling schemes between two nuclear spins located in distant transistors by using a lossless superconducting resonators, mediating the interaction between two nuclear spins via an electron spin. This DG will provide a way forward for the classical electronics industry by bringing it to use for future quantum computers. Our research will provide the building blocks of a quantum processor: Excellent quantum bits formed by the nuclear spin of a dopant located in the transistor channel. We expect our device to show unprecedented capabilities, such as built-in error correction, long coherence and scalability. This DG has the potential to provide Canada with disruptive devices for the microelectronic industry as well as a cutting edge in the race of quantum computation.