Supervisors: Ahsan Nazir, Alex Chin and Terry Rudolph
Non-Gaussian environmental states in strongly-coupled open quantum systems
Everything is influenced by its environment, or surroundings, to some extent. An example of this is the case of an ice cube, understanding how an ice cube behaves depends very much on its environment, whether it is in a drink, a fire or a freezer. The same is true for quantum systems. They are always influenced by their environment to some degree and this can have a significant effect on the way they behave, resulting in imprecise control or loss of quantum features. For this reason isolating quantum systems from environmental influence is a research area that has attracted a great deal of attention over the years and continues to do so. This isolation can require huge experimental effort such as cooling to ultralow temperatures or actively cancelling magnetic fields and other disturbances. The idea is to reduce interactions with the environment to such an extent that they can safely be ignored. Such methods are implemented in order to preserve the often delicate quantum properties of certain systems, particularly those used for quantum simulation and potential precursors to quantum computers.
Complete isolation from environmental effects is often not possible; in this case one enters the field of open quantum systems. When the interactions with the environment are weak there are useful and well-established approximations, but when the environment is strongly coupled to the system we must use alternative approaches to analyse the system and protect against decoherence. In this regime we also open up the possibility of using environmental interactions to our advantage.
In this project we are looking at how environments themselves can display quantum features; in particular the formation of non-Gaussian (quantum) environmental states due to interaction with spin systems. We are investigating how one can gain more insight by modelling the combined system-environment wavefunction with a variational ansatz. This should permit better characterisation of the behaviour of the interacting spin systems, in particular modelling the effect of the interaction on the spin coherence.