Entanglement is a central phenomenon which distinguishes quantum from classical physics. In entangled quantum states, correlations are stronger than any possible in classical systems, which has profound consequences for how we think about nature. Entangled states are also the key resource which give upcoming quantum technologies - such as quantum computers - their power.
Entangled states are generally fragile and difficult to control. They tend to degrade upon any contact with the surrounding environment (which is why quantum computers are so hard to build). Therefore, experimentalists usually work very hard to isolate their quantum systems well and eliminate any sources of noise, for example via cryogenic cooling. However, it has been found that noisy, out-of-equilibrium thermal processes can sometimes be exploited to generate and stabilise entanglement, rather than destroy it. A classical heat engine uses the difference in temperature between a hot and a cold reservoir to create useful work. In a similar manner, it is possible to design quantum thermal machines, which exploits a temperature gradient to generate entanglement.
Entanglement-generating quantum thermal machines have been studied at an abstract level, but not many implementations in real, physical systems have been proposed. In this theoretical project, you will study the implementation of a simple machine with two quantum bits using nitrogen-vacancy (NV) centres in diamond. You will analyse realistic imperfections, interactions, temperature regimes, and control and read-out techniques to determine the feasibility of such a machine and the amount of entanglement, which can be generated.
NV centres are imperfections in the crystal lattice of diamond, where a carbon atom is missing and a nitrogen atom is substituted. This creates a localised quantum system with atom-like properties which can be manipulated and measured using laser light and other electromagnetic fields. NV centers provide a versatile platform for quantum optics experiments. At DTU Physics they are used experimentally for high-sensitivity sensing of magnetic fields, e.g. in biological systems.
Quantum Mechanics. A prior course or experience with quantum information is an advantage.