Phys. Rev. X (in the press); preprint at https://arxiv.org/abs/1812.02175
Reaching temperatures that are low enough to observe many predicted quantum phases is challenging, even with today’s state-of-the-art techniques. This obstacle is one of many preventing the study of extremely low-temperature phenomena with quantum simulators. To overcome this difficulty, Jordan Cotler and co-workers have now proposed a scheme that allows access to low-temperature physics without the need to actually reach the low temperature physically. They dub this technique ‘virtual cooling’.
The central idea explored by the scheme is the link between the density matrix of a system at low temperature and the higher power of the density matrix of the same system at high temperature. The authors showed that the higher power can be accessed through operations involving the exchange of multiple copies of the system. In cold-atom experiments, this is achievable by collective measurements. As an experimental demonstration, the scheme was implemented in a Bose–Hubbard model. Expectation values of an observable at half the temperature of the physical system were derived.