Dressed Interference in Giant Superatoms: Entanglement Generation and Transfer

Abstract

We introduce the concept of giant superatoms (GSAs), where two or more interacting atoms are nonlocally coupled to a waveguide through one of them, and explore their unconventional quantum dynamics. For braided GSAs, this setup enables decoherence-free transfer and swapping of their internal entangled states. For separate GSAs, engineering coupling phases leads to state-dependent chiral emission, which enables selective, directional quantum information transfer. This mechanism further facilitates remote generation of W-class entangled states. Our results thereby open exciting possibilities for quantum networks and quantum information processing.

Figures (6)

• Figure 1: (a) Schematic of a bipartite GSA, formed by a giant atom (atom 1) directly coupled to an additional atom (atom 2) via an interaction $J$. (b) Dispersion relation of the 1D tight-binding chain (modeling the waveguide). Colored lines indicate relevant frequencies and the corresponding wave vectors. (c) Dressed energy levels of the GSA and corresponding phase accumulations. (d) Time evolution of the fidelity $\mathcal{F}$ of $|\psi(t)\rangle$ with respect to $|\psi(0)\rangle$ for different values of $N$. Other parameters are $\omega_{1}=\omega_{2}=0$, $g_{N}/g_{0}\equiv1$, $\xi/g_{0}=15$, $J=\sqrt{2}\xi$, and $|\psi(0)\rangle=\mleft(\sigma_{+}^{(1)}+\sigma_{+}^{(2)}\mright)|G\rangle/\sqrt{2}$.
• Figure 2: (a) Schematic of the braided GSA structure. (b) Time evolution of the atomic coherences $c_{l}(t)c_{l'}^{*}(t)$ for two different values of $\Delta$, starting from an initial state $|\psi(0)\rangle=\mleft(\sigma_{+}^{(1)}+\sigma_{+}^{(2)}\mright)|G\rangle/\sqrt{2}$. Other parameters are $\omega_{1}=\omega_{2}=\omega_{3}-\Delta=\omega_{4}-\Delta=0$, $g_{0}=g_{n_{1}}=g_{N}=g_{n_{2}}$ with $\{n_{1}, N, n_{2}\}=\{1, 4, 5\}$, $\xi/g_{0}=15$, and $J=J'=\sqrt{2}\xi$.
• Figure 3: (a) Schematic of an extended braided structure, where a giant atom is braided with an SSH-type GSA. (b) Time evolution of the excitation probability distribution in the SSH-type GSA with $M=6$ and $\omega_{1}=0$. Inset: time evolution of the fidelity $\mathcal{F}$ of the transferred state with respect to the topological left edge state of the GSA, assuming the giant atom is initially excited. Other parameters are $g_{0}=g_{n_{1}}=g_{N}=g_{n_{2}}$ with $\{n_{1}, N, n_{2}\}=\{1, 2, 3\}$, $\xi/g_{0}=15$, $J_{1}/g_{0}=0.5$, and $J_{2}/g_{0}=1.5$. (c) Schematic of a "structured entanglement lattice" formed by a chain of braided GSAs. Each lattice site encodes an entangled state of the constituent atoms, rather than a single-atom excitation.
• Figure 4: (a) Schematic of the separate GSA structure. High-efficiency chiral state transfer between remote GSAs is allowed by engineering the coupling phase difference $\varphi$. (b) The time-dependent coupling coefficients $g(t)$ and $g'(t)$ together with the time evolution of the fidelities $\mathcal{F}_{\mathrm{I}}$ and $\mathcal{F}_{\mathrm{II}}$. (c) and (d) Time evolution of the field intensity distribution $|a_{n}(t)|^{2}$ for cases I and II (see text for details). Other parameters are $\omega_{j=1,2,3,4}\equiv0$, $N=2$, $n_{1}=100$, $n_{2}=102$, $n_{3}=-102$, $n_{4}=-100$, $\xi/g_{\text{max}}=12.5$, $J=J'=\sqrt{2}\xi$, $\varphi=\pi/2$, $g_{\text{max}}\tilde{\tau}=5.657$, and $\beta/g_{\text{max}}=0.045$.
• Figure 5: (a) Time evolution of the probability distribution (left) and distribution profile at the final time (right) of a structured entanglement lattice, which is formed by a chain of braided bipartite GSAs. The process begins with the fourth GSA prepared in its $|+\rangle$ dressed state. (b) State tomography (density matrix elements $\rho_{n,n'}^{\mathrm{SEL}}$) of the $16$ physical atoms forming the structured entanglement lattice, which indicates a nonlocal multipartite entanglement.