Non-reciprocal Synchronization in Thermal Rydberg Ensembles

Abstract

Optical non-reciprocity is a fundamental phenomenon in photonics. It is crucial for developing devices that rely on directional signal control, such as optical isolators and circulators. However, most research in this field has focused on systems in equilibrium or steady states. In this work, we demonstrate a room-temperature Rydberg atomic platform where the unidirectional propagation of light acts as a switch to mediate time-crystalline-like collective oscillations through atomic synchronization. We find that thermal-motion-induced coupling asymmetry, enabled by counterpropagating probe and control fields, generates persistent oscillations; conversely, co-propagation quenches this effect. We identify, through both numerical and analytical approaches, the criteria for realizing optical non-reciprocity within a synchronization regime. These results provide key insights for chiral quantum optics and promote the on-chip integration of non-reciprocal devices in nonequilibrium many-body systems.

Figures (4)

• Figure 1: Schematic diagram of the optical non-reciprocal synchronization model. (a1) and (b1) Schematics of the system response under co- and counter-propagating probe and coupling fields, respectively. (a2) and (b2) The corresponding energy-level diagram of the three-level Rydberg atom for each configuration.
• Figure 2: The stability analysis and its dynamical simulation. (a) As detuning $\Delta_c$ is varied, the system is partitioned into three distinct regimes based on the number and stability of fixed points: monostable, bistable, and oscillatory. (b) We adiabatically sweep the $\Delta_c$ in both directions to measure the values of $\rho_{rr}$. (c) Time dynamics of $\rho_{rr}$ in the oscillatory regime at $\Delta_c=0$. Simulation parameters are set as follows: $b=2$, $\gamma_{e} = \gamma = 1$, $\gamma_{r} = 10^{-3}\gamma$, $\Delta_p = 0$, $\overline{V}_{rr} = -9\gamma$, $\Omega_{c} = 4.4\gamma$, and $\Omega_{p} = 6\gamma$.
• Figure 3: Non-reciprocal synchronization dynamics. (a1)[(b1)] Dynamics of $\mathrm{Im} [\rho_{eg}(v)]$ for atomic velocities between $-400$ m/s and $400$ m/s under the counter-propagating (co-propagating) condition. (a2)[(b2)] Dynamics of transmission $T$ under co-propagating (counter-propagating) conditions after Doppler averaging. (c) The velocities of the 150 atomic groups used in the simulation are initialized by sampling from the Maxwell-Boltzmann distribution at a temperature of $T_c = 321~\mathrm{K}$. Simulation parameters are set as follows: $\Omega_p = 6\,\gamma$, $\Omega_c = 4\,\gamma$, $\Delta_p = 0$, $\Delta_c = -11\,\gamma$, and $\overline{V}_{rr} = 800\,\gamma$.
• Figure 4: Non-reciprocal synchronized response versus the detuning of the coupling field. (a)[(b)] The oscillation frequencies of transmission under counter-propagating (co-propagating) condition. The color map represents the normalized oscillation amplitude. The simulation parameters are consistent with those in Fig. \ref{['fig:3']}. The inset shows the contrast ratio $\eta$ versus $\Delta_c$.