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Speaker: Amit Ashok, ECE and Optical Sciences, UA
Title: Quantum Limits to Phase and Amplitude Estimation in the High-Strehl Regime
Abstract: Ground-based telescopes are susceptible to seeing, an atmospheric blur that reduces the resolving power of large observatories to only a few arcseconds. Compensating these effects is critical to realizing the potential of both existing and upcoming extremely large telescopes, a challenging task that requires precise wavefront control. Ultimately, this precision is limited by the wavefront sensor (WFS) design and its inherent capacity to accurately encode phase and amplitude aberrations. In this talk, I will discuss how the Quantum Cramer Rao Bound can be employed to derive fundamental limits to phase and amplitude estimation, providing a closed-form expression for the minimum-achievable residual error. However, when estimating phase and amplitude jointly, we find that the QCRB is unachievable, and we must calculate the Holevo’s Cramer Rao Bound (HCRB) that is achievable. I will discuss the closed-form expression for the HCRB and how there is an inherent trade-off between phase and amplitude estimation implied by this bound.