Measurement-Induced Dynamics of Particles and Quasiparticles in a Bose-Hubbard BEC

Measurement plays a crucial role in a quantum system beyond just learning about the system state: it changes the post-measurement state and hence influences the subsequent time evolution; further, measurement can even create entanglement in the post-measurement conditional state. In this work, we study how careful choice of parameters for a typical measurement process on cold atoms systems -- phase contrast imaging -- has a strong impact on both what the experimentalist observes but also on the backaction the measurement has on the system, including the creation and diffusion of quasiparticles emerging from appropriately renormalized measurements of a field theory. We focus on the case of a Bose-Einstein condensate, in the low-temperature and low-momentum limit. Our theoretical investigation allows us to look at both the real particle and quasiparticle dynamics under this measurement, and we find a path to the measurement of quasiparticles directly, as well as control over the measurement-induced creation and diffusion of quasiparticles into different momentum states. This lays a foundation for understanding the effects of both experimental approaches for probing many-body systems, but also more speculative directions such as observable consequences of `spontaneous collapse' predictions from novel models of gravitational decoherence on aspects of the Standard Model.