Southwest Quantum Information and Technology

Determining the asymptotic performance in single-shot coherent state phase estimation of adaptive protocols based on photon counting measurements

Presenting Author: Marco Antonio Rodríguez García, University of New Mexico CQuIC
Contributing Author(s): M. T. DiMario, P. Barberis Blostein, and F. E. Becerra

In recent years, it has been shown that the non-Gaussian measurements can surpass the sensitivity limits of Gaussian measurements in many quantum information protocols, such as state discrimination [PRA 78, 022320 (2008), Nat. Photonics 9, 48–53 (2015)], state preparation [arXiv:2103.10388], and parameter estimation [PRA 79, 040305 (2019), PRL 125, 120505 (2020)]. However, for the problem of single-shot phase estimation in coherent states, there is no proof that the non-Gaussian measurements can outperform the Gaussian limit. This work shows that a set of adaptive phase estimation strategies based on a non-Gaussian measurement consisting of input field displacements, photon counting, and feedback surpasses the best Gaussian estimation strategy known to date. Our proof shows that these non-Gaussian phase estimation strategies have the same functional form as the canonical phase measurement in the asymptotic limit, differing only by a scaling factor in the second order term. The canonical phase measurement is the ultimate measurement sensitivity allowed by physics, but at present, its physical realizations remain unknown for high dimensional states, such as coherent states. While the best-known Gaussian estimation strategy is far below this ultimate limit, these non-Gaussian estimation strategies provide the highest sensitivity among physically-realizable measurements for single-shot phase estimation of coherent states known to date.

(Session 5 : Thursday from 5:00 pm - 7:00 pm)