Quantum many-body information

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Microscopic particles, such as electrons, atoms, and certain microfabricated devices, do not behave as common sense would dictate. Instead, they obey the strange laws of quantum mechanics. These mathematical laws predict for instance that a microscopic particle can be at two places at the same time. While it is hard, if not impossible, to get an intuitive sense about these laws, they are mathematically well understood, they have lead to many scientific predictions, and they have never been contradicted by an experiment. It is by studying the laws of quantum mechanics that devices such as the laser and the transistor were theoretically discovered, before being fabricated. These two devices led to the information revolution, which has impacted all spheres of human activity.While quantum mechanics is at the heart of the information age, the information itself remains classical: the bits processed by a smartphone do not take two different values at a given time, or any such quantum weirdness. Quantum information science is preparing the next information revolution, where quantum mechanical effects are harnessed to enhanced our information processing ability. Quantum communication systems enable unconditionally secure private communication (in contrast to current cryptographic schemes that can be broken with sufficient computing power). Quantum information processors offer an exponential speed-up for certain computations such as factoring integers (with applications in code breaking) and the simulation of quantum mechanical systems (with applications in physics, chemistry, and biology). And these few examples are only the tip of the iceberg.But quantum systems are extremely vulnerable to errors of all kinds, which poses major roadblock to the development of these technologies. If left unattended, these errors will quickly corrupt the quantum information. Scientists have devised fault-tolerant quantum computation, a set of methods to cope with these errors, which is the central theme of my research. While this remedy is well founded theoretically, it entails an explosion of resources required to quantum compute. For instance, with existing schemes, it takes several millions of noisy quantum bits to do the job of a single clean quantum bit. This overhead represents a serious obstacle to the realization of certain quantum technologies, and the main objective of this research proposal is to find theoretical methods to significantly reduce that overhead. Obviously, improving the quality of the physical devices is one way to suppress the overhead. However, it is by improving the software, i.e. the fault-tolerant techniques themselves, that the most significant improvement can be obtained.In the next five years, my NSERC supported research will combine ideas and techniques from theoretical computer science and many-body physics in innovative ways to reduce this overhead. This will be achieve by 1) Enhancing the ways in which fault-tolerant techniques are currently being decoded; 2) Devising new ways to manipulate information fault-tolerantly; and 3) Discovering new phases of matter that naturally protect quantum information. Much like the field itself, my approach is multidisciplinary. I have acquired a unique expertise in these research areas and have assembled an interdisciplinary team of talented young researchers. With this team, I will continue to propose new innovative fault-tolerant methods that will take quantum information processing from a theoretical dream to reality. Canada is already at the forefront of quantum information, and my program will contribute to increase our knowledge in this field and create opportunities for students to learn and apply this knowledge.