Single photon (qubit) probes

Can we probe and control the quantum mechanical properties of complex molecules?

Optics lab

Background

ChartA major goal of quantum physics is to use quantum mechanics to build efficient nanoscale information processors. This requires the control of quantum phenomena at the level of single electrons, where they behave as waves that extend over a region of space. The electron-waves, then, can combine and superpose constructively and destructively when their amplitudes are in step – this constant periodicity is called coherence and is necessary for quantum computing. A major obstacle to building such computers is that constant amplitude-relationships between electron-waves – and even within a single wave – are so short-lived that they don’t allow time for computing operations. This is because heat from surroundings lengthens the electron-waves randomly and unequally. For this reason quantum experiments need temperatures as low as -272 degrees.

A growing body of evidence suggests that protein-sized biomolecules could harbour long-lived quantum states. This is surprising given the large size and warm environments of the molecules, which are highly unfavourable to the extremely fragile quantum states. Ultimately we would like to copy their trick. That goal is highly ambitious.

Aim

Optical lensesThe ultimate and most sensitive way of probing complex systems is by using other quantum systems as probes. Such capability does not exist yet. We will develop a state-of-the-art experimental quantum probe to test the properties of single-molecules using single-photons (quantum objects). By recording and analysing the statistical distributions of photons scattered by a single-molecule, we will infer how well electron quantum states are confined or smeared inside the molecule, how efficiently the photons and electron states can encode information bits, and how much useful work can be extracted from them.

Our enabling technology is a highly efficient micron-sized optical microcavity (lens-system) that channels the extremely faint light-signal when single photons are emitted.

Our experimental effort covers quantum physics and chemistry, material sciences and molecular quantum optics.

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