Experimental observation of curved light-cones in a quantum field simulator

Abstract

We investigate signal propagation in a quantum field simulator of the Klein–Gordon model realized by two strongly coupled parallel one-dimensional quasi-condensates. By measuring local phononic fields after a quench, we observe the propagation of correlations along sharp light-cone fronts. If the local atomic density is inhomogeneous, these propagation fronts are curved. For sharp edges, the propagation fronts are reflected at the system’s boundaries. By extracting the space-dependent variation of the front velocity from the data, we find agreement with theoretical predictions based on curved geodesics of an inhomogeneous metric. This work extends the range of quantum simulations of nonequilibrium field dynamics in general space–time metrics.

Identifying diffusive length scales in one-dimensional Bose gases

“…Refs. [27][28][29][30][31]). However, when considering the underlying microscopic Hamiltonian (here the Lieb-Liniger Hamiltonian), phonons are superpositions of the true eigenstates and therefore do not have infinite lifetime.…”

“…Our analysis also provides a proxy for the phonon lifetime, enabling one to gauge the applicability of a phonon basis to describe dynamics. Phonon bases have been used extensively to describe quantum field simulators realized with ultracold atoms [25][26][27][28][29][30][31]; identifying the time scales at which a low-energy effective theory remains valid is thus beneficial for a number of applications.…”

Rotating curved spacetime signatures from a giant quantum vortex

“… Gravity simulators 1 are laboratory systems in which small excitations such as sound 2 or surface waves 3 , 4 behave as fields propagating on a curved spacetime geometry. The analogy between gravity and fluids requires vanishing viscosity 2 – 4 , a feature naturally realized in superfluids such as liquid helium or cold atomic clouds 5 – 8 . Such systems have been successful in verifying key predictions of quantum field theory in curved spacetime 7 – 11 .…”