Dark States of Multilevel Fermionic Atoms in Doubly Filled Optical Lattices

We propose to use fermionic atoms with degenerate ground and excited internal levels ($F_g\to F_e$), loaded into the motional ground state of an optical lattice with two atoms per lattice site, to realize dark states with no radiative decay. The physical mechanism behind the dark states is an interplay of Pauli blocking and multilevel dipolar interactions. The dark states are independent of lattice geometry, can support an extensive number of excitations, and can be coherently prepared using a Raman scheme taking advantage of the quantum Zeno effect. These attributes make them appealing for atomic clocks, quantum memories, and quantum information on decoherence free subspaces.

Figure 1

Summary of proposed platform. (a) Fermionic atoms with an $F_g\to F_e$ transition from ground (blue) to excited levels (red). (b) Examples of dipole exchange interaction between different levels mediated by a photon (red wave). (c),(d) Optical lattice with two atoms per site occupying the motional ground state only. (e) Example of a decay channel blocked by Pauli exclusion.

Figure 2

Dark states for two fermions on a single site for different internal level structures.

Figure 3

(a) Raman excitation scheme for $F_g=F_e=F_s=1/2$ and ${\mathbf{e}}_z$ polarized light. (b) Excitation of ${|D_0⟩}_{\{1/2,1/2\}}$ for ${}^{171}\mathrm{Yb}$ level structure with ${\mathrm{\Omega }}^{\mathrm{eff}}=0.03\mathrm{\Gamma }$. (c) Excitation of ${|D_0⟩}_{\{9/2,9/2\}}$ for ${}^{87}\mathrm{Sr}$ level structure with ${\mathrm{\Omega }}^{\mathrm{eff}}=0.001\mathrm{\Gamma }$. (d) Resonant Ramsey sequence for ${\mathrm{\Delta }}_z/\mathrm{\Gamma }=\{0,4,8,16,32\}{10}^{-3}$ from top to bottom.