Deterministic entanglement of two neutral atoms via Rydberg blockade

We demonstrate the deterministic entanglement of two individually addressed neutral atoms using a Rydberg blockade mediated controlled-not gate. Parity oscillation measurements reveal a Bell state fidelity of $F=0.58\pm 0.04$, which is above the entanglement threshold of $F=0.5$, without any correction for atom loss, and $F=0.71\pm 0.05$ after correcting for background collisional losses. The fidelity results are shown to be in good agreement with a detailed error model.

Figure 1

(a) Experimental geometry, (b) relevant levels of ${}^{87}\mathrm{Rb}$, and (c) calculated blockade shift $\mathsf{B}$ and double excitation probability $P_2$. The relative probability distribution $P(|z_1-z_2|)$ assumes a trapping potential $U/k_B=4.5\hspace{0.5em}\mathrm{mK}$, waist of the 1064-nm trapping light of $w=3.2\hspace{0.5em}\mu \mathrm{m}$, and atom temperature $T=175\hspace{0.5em}\mu \mathrm{K}$.

Figure 2

(a) Ground Rabi flopping on targeted site with neighboring site crosstalk in upper panel and (b) Rydberg Rabi flopping on targeted site, with neighboring site crosstalk and flopping blocked by prior excitation of the neighboring site in upper panels. The flopping curves are based on an average of about 100 measurements for each point.

Figure 3

(a) Experimental sequence: pulses 1 and 5 are ground Rabi $\pi /2$ pulses; pulses 2 and 4 are Rydberg $\pi$ pulses; pulse 3 is a Rydberg $2\pi$ pulse. Measured probabilities for state preparation (b) and $H$$-$cz cnot (c). The reported matrices are based on an average of about 100 data points for each matrix element.

Figure 4

Measured probabilities for preparation of Bell states $|B_1\rangle ,|B_2\rangle$ and parity oscillation signal obtained from $|B_1\rangle$. The upper inset gives parameters found from fitting the observed parity signal together with expected values derived from measured experimental parameters. The lower inset shows the stochastic phase limited fidelity versus temperature (see text for details).