Figure 1

Experimental setup for teleportation between remote single-atom quantum memories. Single atoms (gray spheres $A$ and $B$) are trapped in optical cavities (blue cones) in independent laboratories at a distance of 21 m. (a) Entanglement is generated between atom $B$ and an ancilla photon $C$. (b) The atomic qubit at node $A$ is mapped onto a photonic qubit $A^{\prime }$ and a Bell-state measurement between the two photons is performed. (c) Detection of a $|{\Psi }^{-}⟩$ event heralds the successful teleportation of the atomic qubit from node $A$ to node $B$.Reuse & Permissions

Figure 2

Bell-state measurement using time-resolved two-photon interference. (a) The photons (red and orange) overlap at an NPBS. Two single-photon detectors (gray semicircles) and a polarizing beam splitter (PBS) in each output port of the NPBS allow us to discriminate between horizontally ($H$) and vertically ($V$) polarized photons. Correlations between different detectors either herald a $|{\Psi }^{-}⟩$ or a $|{\Psi }^{+}⟩$ Bell state or indicate that the photons did not interfere (ni). (b) Result of a time-resolved coincidence measurement for photons of identical ($N_{\mathrm{ni}}$, blue filled bars) and orthogonal ($N_{|{\Psi }^{-}⟩}$, black open bars) polarization in opposite output ports of the NPBS. The number of coincidences between photons with the same polarization is strongly suppressed. The red data points show the ratio $N_{\mathrm{ni}}/N_{|{\Psi }^{-}⟩}$ between no-interference and $|{\Psi }^{-}⟩$ events. The error bars indicate the statistical standard error. (c) Interference contrast $C$ (red points) and relative number of evaluated counts (blue diamonds) as a function of the maximal detection time difference for a two-photon correlation in different output ports of the NPBS. By postselecting on short detection time differences, the interference contrast can be greatly enhanced. All statistical error bars are smaller than the respective symbols.Reuse & Permissions

Figure 3

Teleportation fidelity as a function of the interference contrast. Increasing the contrast by using time-resolved BSM (Fig. 2) increases the fidelity of the whole teleportation protocol. (a) The plot shows data for $|{\Psi }^{-}⟩$ teleportation events. Black triangles are measured average fidelities for the two input states $|{\downarrow }_x⟩$ and $|{\uparrow }_x⟩$. The blue diamonds are averages over the other four input states given in Table . The red points show the mean fidelity averaged over all six input states. The red line is the theoretical expectation [Eq. (3)] for the parameters ${\mathcal{F}}_{\mathrm{ent}}=89\%$ and ${\mathcal{F}}_A=95\%$ estimated from independent measurements and including imperfections in the readout [20]. The dashed lines indicate the theoretically expected behavior for the subset of data in the respective color [20]. The error bars indicate the statistical standard error. (b), (c) Reconstructed Bloch sphere [19] of the teleported state, with no additional temporal filtering applied ($C=64\%$) (b) and for a contrast of $C=93\%$, i.e., only taking correlations with a maximal detection time difference of 80 ns during the BSM (c). The size of the colored ellipsoids represents the statistical standard error.Reuse & Permissions