(open quantum) Research

Any (open) quantum system is unavolidably affected by its environment. Modelling open-system dynamics accurately is a formidable challenge—not only because of the complexity of typical environments, but also because we often know very little about them. The mission of the theory of open quantum systems is to transform such an herculean task into manageable calculations. But simplifying open-system dynamics comes at a cost—many approximations need to be made. Questioning their range of validity, accuracy, and thermodynamic consistency has paved the way towards a rich and active area of research.

At the Exeter Open Quantum Systems group, we work to shed new light on dissipation and energy transport across nanoscale systems, which could be used ro model, e.g., the registers of a quantum computer, or proteins within a photosynthetic complex.

The methods of open quantum systems can be applied to realistic models for a quantum sensor—e.g., an atomic impurity sensing the temperature of an ultra-cold atomic gas—when blended with the toolbox of quantum parameter estimation. For instance, one can obtain insights on how to optimise the sensors' design (should the impurity–gas interactions be tuned to be strong or weak?); what to measure (is absorption imaging optimal for thermometry?); or even how to interpret the measured data correctly (which metrological bounds are more meaningful when data is scarce?). This is the remit of "quantum thermometry".

At the Exeter Open Quantum Systems group, we work to improve the modelling of practically relevant scenarios. For instance, developing new tools to calculate metrological bounds on non-linear open quantum systems, or combining open-system modelling with bayesian parameter estimation to find new thermometric protocols that can work accurately with limited data.

To read more on quantum thermometry take a look to our recent topical review on the subject!

Under certain conditions, the physics of an individual (open) quantum system appears to follow the laws of macroscopic thermodynamics. This intriguing (and decades-old) observation suggests that thermodynamic behaviour might emerge from open-system theory, and has triggered a roaring interest on "quantum thermodynamics".

We are interested in its more practical side; namely, the characterisation and performance optimisation of quantum heat devices—especially refrigerators; and in drawing the quantum–classical boundary in quantum thermodynamics (can quantumness be exploited to our advantage in nanoscale thermodynamcis? If so, how?) Specifically, we are looking into extending quantum thermodynamics to non-linear open systems which dissipate strongly into engineered environments.

We have recently edited a book on quantum thermodynamics collecting the recent progress in the field. Why not read (most of) it?