Center for Quantum Technologies, National University of Singapore
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Publications (arXiv)
PhD thesis - Information flow at the quantum-classical boundary
MSc thesis - Monte Carlo study of the magnetic flux lattice fluctuations in high-temperature superconductors
Quantum information

Physics aims to predict the result of observations. Any observation is a physical interaction between the observer and the system being observed. The information gained during that interaction does not only depend on the state of the system, but also on the precise way that we choose to interact with it. Any particular such choice is called an observable. Before the discovery of quantum mechanics, physicists relied on the "classical" assumption that there always exists in principle one best way of making an observation, such that the information obtained allows one to deduce what the result of any other type of observation would have been.

However our understanding of quantum mechanics tells us that there are physical regimes (typically microscopic) where this principle does not hold, and hence it is valid only approximately in special circumstances. It is now known that there exists an infinite number of incompatible ways of observing any given system, which each yield fundamentally different information about it (e.g. Heisenberg's uncertainty principle).

This can be alternatively conceived as follow: an observation only extracts classical information from a physical system. The system actually encode a more general type of information which has no classical counterpart, and which is called quantum information. Contrary to classical information, quantum information cannot be duplicated (no-cloning theorem), which is why an observer cannot acquire it in its entirety.

One can naturally use this property for cryptography: quantum information is fundamentally private since it cannot be shared. In addition, computations performed on quantum rather than classical information could solve problems which are classically intractable (e.g. factoring, simulation of quantum processes).

Research interests

My interests lie at the frontier between the fully quantum and the fully classical regimes. How are classical observations effectively reduced to a single quantum observable (decoherence)? How is this phenomenon related to the size or other properties of the object under study? What is its relation to thermal equilibrium? Can it be avoided, even for objects which possess different characteristics (e.g. through quantum error correction)? - a question which needs to be solved if one hope to build a useful quantum computer.