A fundamental tenet of quantum mechanics is that measurements change a system's wavefunction to that most consistent with the measurement outcome, even if no observer is present. Weak measurements produce only limited information about the system, and as a result only minimally change the system state. In this context, the interaction of a nearly closed quantum system with its environment can be described as a continuous weak measurement process. Bose-Einstein condensates (BECs) offer multiple weak measurement techniques, that yield a controlled reservoir and consequently allow time-resolved study of the system evolution. We theoretically and experimentally characterize the quantum projection noise in atomic BECs weakly measured by the light scattered from a far-from resonant, i.e., dispersivly interacting, laser beam. We quantify the resulting wavefunction change with two observations: the contrast in a Ramsey interferometer, and the deposited energy. Next, we present a versatile high-resolution ultracold atom microscope: a combined hardware/software system that recovers near-diffraction limited performance and minimizes the information loss. Our high-fidelity digital correction technique reduces the contribution of photon shot noise to density-density correlation measurements, which would otherwise contaminate the quantum projection noise signal in weak measurements . We demonstrate our aberration compensation technique using phase contrast imaging, a dispersive homodyne detection technique directly applicable to quantum back-action limited measurements.
 E. Altuntas, and I. B. Spielman, Physical Review Research, 3, 043087 (2021).
|Presenter name||Emine Altuntas|
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