High-fidelity two-photon geometric gates with a single-pulse Rydberg blockade scheme

Laser-excited Rydberg atoms provide controlled long-range interaction desired for atomic [1-5] and photonic [6-10] quantum technologies. In this talk, I present an approach to realize high fidelity CZ photonic gate by storing both control and target photons within an atomic ensemble [11] using non-Rydberg electromagnetically induced transparency (EIT) followed by a fast, single-step Rydberg excitation with global lasers. The proposed scheme [12] operates by relative intensity modulation of two lasers used in Rydberg excitation. Bypassing the conventional p-gap-p schemes [1,6,7], the operation features continuous laser shielding of the Rydberg atoms from the environment noise. The optical depth is optimized and the experiment is made simpler by the complete spatial overlap of stored photons inside the blockade radius. Here, a coherent operation is carried out in a region that was dissipative in earlier Rydberg photonic gates [6,7]. Encountering the primary sources of imperfection, this study comes to the conclusion that 99.7% fidelity can be achieved under realistic experimental conditions by taking into account the spontaneous emission of the Rydberg and intermediate levels, population rotation errors, Doppler broadening of the transition lines, storage/retrieval efficiency, and atomic thermal motion induced decoherence.

References:
1- M. Khazali, Klaus Mølmer, Phys. Rev. X 10, 021054 (2020).
2- M. Khazali, Quantum 6, 664 (2022).
3- M Khazali, Phys. Rev. Research 3, L032033 (2021)
4- M. Khazali, Phys. Rev. A 98, 043836 (2018)
5- M. Khazali, H. W. Lau, A. Humeniuk, C. Simon, Phys. Rev. A 94, 023408 (2016)
6- M. Khazali, K. Heshami, C. Simon, Phys. Rev. A 91, 030301 (2015)
7- M. Khazali, C. Murry, T. Pohl, Phys. Rev. Lett. 123, 113605 (2019)
8- M. Khazali, K. Heshami, C. Simon J. Phys. B, 50, 21 (2017)
9- M. Khazali, IJAP 10, 19 (2021)
10- Khazali, Mohammadsadegh. "Applications of Atomic Ensembles for Photonic Quantum Information Processing and Fundamental Tests of Quantum Physics." Ph.D. thesis, University of Calgary (2016).
11- H Kaviani, M Khazali, R Ghobadi, E Zahedinejad, K Heshami and C Simon, New J. Phys. 15, 085029 (2013)
12- Khazali, Mohammadsadegh. "All optical quantum information processing via a single-step Rydberg blockade gate." arXiv preprint arXiv:2211.06998 (2022).