One person's ancilla is another person's target

My latest preprint is finally out for everyone to read! In this work we improve on models of Heat-Bath Algorithmic Cooling (HBAC) protocols taking place in a NV centre in diamond. Find it at Physical Review Letters.

We use the model to analyse data extracted from an experiment that reaches the cooling limits of the protocol. In the experimental realization the reset qubits thermalize to two slightly distinct temperatures, which is in contrast to the previously known results determining the cooling limits, that depended on having a single heat bath. By solving the model analytically we are thus able to extend our knowledge of the lowest temperatures achievable to a system with two heat baths.

Our model is capable of better accounting the experimental intricacies of implementing HBAC in a lab, in a minimal way: our refinements do not involve coherences, and we identify separate ways to control the convergence rate towards the steady state and to control the asymptotic temperature values.