Master Thesis Defense: Amelia Jade White

Simulating molecular vibrations using quantum-dot induced non-linearities

Photon-photon interaction is required in order to realise photonic quantum computing applications. One way to mediate a photon-photon interaction is via a quantum-dot induced non-linearity.

In this thesis, we use linear optical circuits together with two-photon scattering from a quantum-dot to simulate molecular vibrations of molecules with anharmonicity. This simulation is compared to an otherwise equivalent simulation that uses a single-mode Kerr non-linearity. The quantum-dot scattering is seen to cause significant distortion of the optical pulse.

By changing the spectral width of the input state and the detuning between the input state and the quantum dot, it is possible to reduce this distortion. In this regime of favourable parameters, we find agreement between the simulation using the quantum dot non-linearity, and the simulation using the idealised non-linearity.

In particular, fidelities of 98% and 94% were found over 20 and 50 so-called unit cells, where one unit cell containing two quantum-dots is mapped to one unit cell containing two Kerr non-linearities.

These simulations are used to simulate the molecular vibrations of stretch modes in water with a fidelity of 96% over 12 unit cells. This simulation can in principle be scaled to larger number of modes and photons, which could be used to simulate the dynamics of molecules with many degrees of freedom. Using quantum computers for this purpose is a key area of interest in drug mechanism and discovery.