Weak Measurement Induced Phonon Fluctuations in a Bose-Einstein Condensate

Non-destructive imaging methods are weak measurement techniques that offer new opportunities for understanding the system-reservoir dynamics of many-body systems. Weak measurements yield a controlled reservoir and consequently allow time-resolved study of the system evolution. We consider the quantum backaction induced by weak measurements in quasi-one dimensional 87Rb Bose-Einstein condensates (BECs) using a common non-destructive imaging technique: phase contrast imaging. In this talk, I first discuss the theoretical model for weak measurement via phase contrast imaging (PCI) [1]. I then describe our experimental work and novel methodology of eliminating artifacts present in imperfect imaging systems. Weak measurements provide noisy information about the ultracold atoms system, and thus aberration-compensation is crucial for extracting the underlying quantum phenomena. Next, I present our preliminary results on the phonon fluctuations that result from the quantum backaction induced by repeated PCI of the condensate. Finally, I will discuss possible feedback control protocols for future applications of Hamiltonian engineering using weak measurements and feedback. 

[1] Hurst et. al., Phys. Rev. A 99, 053612 (2019).