Measurement plays a crucial role in a quantum system beyond just learning about the system state: it changes the postmeasurement state and hence influences the subsequent time evolution; further, measurement can even create entanglement in the postmeasurement conditional state. In this work, we study how a careful choice of parameters for a typical measurement process on cold atom systems—phase-contrast imaging—strongly impacts both what the experimentalist observes and the measurement backaction on the system, including the creation and diffusion of quasiparticles emerging from the quantum many-body dynamics. We focus on a Bose-Einstein-condensate array in the low-temperature, low-momentum limit. Our theoretical investigation identifies regimes in which the imaging light probes either bare atomic or Bogoliubov quasiparticle dynamics. Furthermore, we show that, together with a weak global drive, appropriate tuning of the measurement bandwidth enables direct probing of Bogoliubov quasiparticles while controlling the measurement-induced creation and diffusion of quasiparticles across momentum modes. These results clarify how the measurement protocol determines both the observed excitations and the corresponding measurement backaction in weakly interacting Bose-Einstein condensates.

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• Cold atoms & matter waves
• Quantum metrology
• Quantum sensing