Super-dephasing in collective atom-atom interactions and its applications in quantum sensing

Collective atom-light interactions have received considerable attention due to their potential applications in quantum information processing and quantum metrology. Atoms or spins interacting with fluctuating electromagnetic (EM) modes can underdo two non-unitary processes -- pure dephasing and spontaneous emission. The dissipative collective emission processes (e.g., superradiance) originate from interactions with EM modes in resonance with atoms and have received much interest. Meanwhile, the analogous non-dissipative collective dephasing phenomena mediated by EM environments remain poorly understood. In this talk, we will introduce the nano-EM super-dephasing phenomenon arising in the photonic environments near materials. We show that collective dephasing in this nano-EM environment is enhanced by over 10 orders of magnitude compared to free space or cavities. This giant enhancement originates from long-range correlations in off-resonant, low-frequency evanescent EM fluctuations, which lead to collectively accelerated (super-) or suppressed (sub-) dephasing in entangled states without photon emission. We further demonstrate unique scaling laws of super-dephasing in GHZ states that are different from the conventional N^2 scaling of superradiance. Finally, we discuss how to exploit this nano-EM collective dephasing to improve quantum sensing sensitivity and probe correlations in two-dimensional materials that may not have prominent effects on individual qubits.