Experimental verification of the formation of stationary dark-state polaritons dressed by dipole-dipole interaction

Bongjune Kim^1*, Ko-Tang Chen¹, Kuei-You Chen¹, Yu-Shan Chiu¹, Chia-Yu Hsu¹, Yi-Hsin Chen², Ite A. Yu^1,3

¹Dept of Physics, National Tsing Hua University, Hsinchu, Taiwan
²Dept of Physics, National Sun Yat-sen University, KaoHsiung, Taiwan
³Center for Quantum Science and Technology, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Bongjune Kim, email:upfe11@gmail.com

Bose-Einstein condensation (BEC) of dark-state polaritons (DSPs) was proposed in Ref.[1]. The DSPs represent the superpositions of probe photons and atomic ground-state coherences. A light effective mass of DSP can be expected to have higher critical temperature than atomic BEC. The lifetime is expected to be longer than exciton-polariton BEC. Furthermore, compared to two-dimensional exciton-polariton BEC, a three-dimensional DSP-BEC system is achievable.
In this study, we proposed a platform of stationary dark-state polaritons (DSPs) dressed by the dipole-dipole interaction (DDI) to achieve Bose-Einstein condensation (BEC) of DSP and experimentally demonstrated the formation of the scheme [2]. The scheme was consisted of the Λ-type electromagnetically induced transparency system and the two-photon transition to drive a Rabi oscillation between a ground state and a Rydberg state. The scheme can overcome the large phase mismatch problem in the direct formation of the stationary Rydberg polaritons.
The formation of the stationary-DSP dressed by DDI was verified by the measurement of attenuation coefficients and phase shift with various input probe Rabi frequencies which can control the strength of DDI. For further verification, attenuation coefficients and phase shift were measured with various principal quantum numbers. The experimental data was theoretically predicted by the optical Bloch equations of the density-matrix operator and the Maxwell-Schrodinger equations. The predictions were in good agreement with the experiment data. Based on the formula in Ref.[1], we estimated the BEC transition temperature, the stationary-DSP temperature, and the elastic collision rate at the present experimental condition to verify the possibility as a platform for the DSP-BEC. The stationary-DSP temperature was well below the BEC transition temperature.

References
[1] M. Fleischhauer, J. Otterbach, and R.G. Unanyan, Phys. Rev. Lett. 101, 163601 (2008).
[2] B. Kim, K.-T. Chen, K.-Y. Chen, Y.-S. Chiu, C.-Y. Hsu, Y.-H. Chen, and I. A. Yu, Phys. Rev. Lett. 131, 133001 (2023).

Keywords: stationary dark-state polariton, Rydberg atom, Dipole-Dipole interaction