Speaker
Description
The development of efficient techniques to cool quantum systems has been
instrumental for the emergence of quantum technologies. Preparing a many-body quantum system in a pure target state is, for example, a prerequisite for its use to study complex interactions or implement quantum computations. State preparation needs to work irrespective of the initial state of the quantum system and thus requires reduction of both system energy and entropy. A powerful way to engineer such desired dissipative dynamics is by coupling to auxiliary qubits. While protocols where the number of auxiliary qubits increases with the system size are of limited practical usefulness, "dilute" cooling is possible for certain many-body quantum systems. I will discuss two examples of frustration-free one-dimensional spin chains and show that they can be driven into their (topological) ground state by measuring two adjacent system sites only. I will then ask what it takes to make the auxiliary qubits resemble a cold bath in nature. A natural cold bath will cool a quantum system without any knowledge of the system’s spectrum or quantization axis. Assuming a reservoir of auxiliary qubits prepared in their ground state, I will introduce a protocol for universal cooling of many-body quantum systems.
