Mach-Zehnder interferometer for in-situ characterization of atom traps

Abstract

Manipulating cold atoms in traps is a key tool for numerous realizations of quantum simulators and quantum sensors. They require accurate modeling and characterization of the underlying trapping potentials. We introduce a technique based on the Mach-Zehnder interferometer for in-situ characterization of weakly anharmonic potentials. By simulating the interferometer in an optical dipole trap, we can accurately determine its trap frequency and upper bounds onto anharmonicity magnitudes.

Figures (7)

• Figure 1: (top) Harmonic trapping potentials of two internal states $\left| 1 \right\rangle$ (dashed) and $\left| 2 \right\rangle$ (solid) with spatial shift between the trap centers (minima). (bottom) Interferometer pulses (thick arrows) separated by time $T$ transfer atoms between the two states, automatically leading to moving and, generally, breathing wavepackets. The shown Mach-Zehnder configuration leads to a periodic two-path-interference of an upper (blue) and lower (red) wavepacket whenever the positions $q$ of their center-of-mass are sufficiently close.
• Figure 2: (a) Positions $q$ and (b) widths $\sigma$ of the two wavepackets at the time of the final pulse $2T$ as a function of the time $T$ between the pulses. Here the parameters listed in Tab. \ref{['tab:example']} are used. (c) Signal $P_2$ of the interferometer for two pulse phase contributions $\Delta \Phi_\text{P}$. When $T$ matches the trap periods $2 \pi / \omega_2$ or $2 \pi / \omega_1$ (vertical lines) the wavepackets are identical at the last pulse and the phase $\varphi$ vanishes.
• Figure 3: Signal $P_2$ of the 1D and 3D MZI for the time $T$ close to $10 \pi / \omega_2$. The parameters listed in Tab. \ref{['tab:example']} and the phase difference $\Delta \Phi_\text{P} = \pi / 2$ are used.
• Figure 4: (a) Interferometer signals $P_2$ as a function of the pulse separation $T$. The trap parameters are listed in Tab. \ref{['tab:example']}. Solid lines are simulations of a Rabi-coupled two-level Hamiltonian including the influence of position-dependent detunings. (b) Trap frequencies $\omega$ and corresponding fits determined by simulating the 3D MZI inside an optical dipole trap for different trap separations $|z_{0,1} - z_{0,2}|$ and initial states.
• Figure S1: Interferometer signals $P_2$ as a function of the time between the pulses $T$ obtained by simulating the MZI in a crossed optical dipole trap as discussed in the main text ($\Delta \Phi_\text{P} = 0$).