Adiabatic quantum state manipulation of single trapped atoms

We use microwave-induced adiabatic passages for selective spin flips within a string of optically trapped individual neutral Cs atoms. We position-dependently shift the atomic transition frequency with a magnetic field gradient. To flip the spin of a selected atom, we optically measure its position and sweep the microwave frequency across its respective resonance frequency. We analyze the addressing resolution and the experimental robustness of this scheme. Furthermore, we show that adiabatic spin flips can also be induced with a fixed microwave frequency by deterministically transporting the atoms across the position of resonance.

Figure 1

Experimental setup. See text for details.

Figure 2

Spectrum of adiabatic population transfer. Each data point shows the average population transfer to state ∣1⟩ for ten shots with about five atoms each. The solid line is a theoretical fit, derived from optical Bloch equations. The maximum population transfer efficiency predicted by theory is 100%. The fit yields $95\pm 0.4\%$, limited mainly by imperfect initialization of state ∣0⟩, which depends critically on the polarization purity of the optical pumping laser.

Figure 3

Position-dependent adiabatic population transfer of individual atoms in an inhomogeneous magnetic field. The graph shows the population transfer induced by the AP as a function of the position offset $\Delta x$ along the trap axis. Each data point is obtained from about 40 single atom measurements. The solid line is a theoretical fit of Eq. (4) with $P_{\max }=93\pm 1.7\%$ limited by imperfect state initialization.

Figure 4

Transport-induced adiabatic passages. (a) A sketch of the temporal variation of the atom-field detuning during the transport of duration $\tau$ [see Eq. (5)]. (b) The population in state ∣1⟩ after transport as a function of $1∕\tau$. Each data point is an average over ten shots with about five atoms each. The solid line is the theoretical population transfer, neglecting the thermal motion of the atoms and decoherence of Rabi oscillations.