The static and dynamic properties of many-body quantum systems are often well described by collective excitations, known as quasiparticles. Engineered quantum systems offer the opportunity to study such emergent phenomena in a precisely controlled and otherwise inaccessible way. However, as these engineered systems become larger and more complex, conventional tomograhic methods for characterising their states and processes soon become either ineﬃcient or of limited applicability. New methods are required to verify what has been built in the laboratory and to study the properties of these fascinating systems.
Here, we present a spectroscopic technique to study artificial quantum matter and use it for characterizing quasiparticles in a many- body atomic system of trapped atomic ions. Our approach is to excite combinations of the system’s fundamental quasiparticle eigenmodes, given by delocalized spin waves. By observing the dynamical response to superpositions of such eigenmodes, we extract the system dispersion relation, magnetic order, and even detect signatures of quasiparticle interactions. Our technique is not limited to trapped ions, and it is suitable for verifying quantum simulators by tuning them into regimes where the collective excitations have a simple form.
P. Jurcevic, P. Hauke, C. Maier, C. Hempel, B. P. Lanyon, R. Blatt, and C. F.Roos, Phys. Rev. Lett. 115, 100501 (2015)