Abstract The key role of π- and π/2-pulses in atom interferometry has been widely recognized as their efficiency affect the overall performance of atomic interferometers. The inefficiencies are evident when using thermal cloud atoms as the field interaction does not compensate for the atom velocity. Temporal pulse shaping offers a solution to this issue by balancing the effect of the temporal shape of the mirror pulse in thermal cold atom interferometry by testing pulse shapes beyond the standard rectangle including Gaussian-like, Sinc-like, optimized Band-selective Uniform Response Pure-phase family, and optimized Gaussian Cascade family. We unveiled a correlation between the π-pulse fidelity and the overall interferometer contrast function. We also found robust pulse sequences with respect to initial atom velocities that offer contrast as high as 0.7 compared to standard rectangle sequences with values of 0.2. The investigated pulse sequences offer an efficient way to improve the performance of atom interferometers, increasing the potential of thermal cold atom interferometry.
Abstract The key role of π- and π/2-pulses in atom interferometry has been widely recognized as their efficiency affect the overall performance of atomic interferometers. The inefficiencies are evident when using thermal cloud atoms as the field interaction does not compensate for the atom velocity. Temporal pulse shaping offers a solution to this issue by balancing the effect of the temporal shape of the mirror pulse in thermal cold atom interferometry by testing pulse shapes beyond the standard rectangle including Gaussian-like, Sinc-like, optimized Band-selective Uniform Response Pure-phase family, and optimized Gaussian Cascade family. We unveiled a correlation between the π-pulse fidelity and the overall interferometer contrast function. We also found robust pulse sequences with respect to initial atom velocities that offer contrast as high as 0.7 compared to standard rectangle sequences with values of 0.2. The investigated pulse sequences offer an efficient way to improve the performance of atom interferometers, increasing the potential of thermal cold atom interferometry.
Abstract Laser frequency fluctuation and atomic thermal motion can lead to errors in pulse area and detuning in cold atom interferometry, thereby reducing measurement stability and fringe contrast. To address this issue, we investigate the use of super-Gaussian pulses, which are characterized by smooth temporal profiles and centralized energy distribution, in the beam-splitting and reflection stages of an atom interferometer. In this theoretical and numerical study, we compare the performance of rectangular, Gaussian, and 2nd- to 10th-order super-Gaussian pulses subject to deviations in pulse area and detuning. Our results show that both Gaussian and super-Gaussian pulses offer a significant advantage over traditional rectangular pulses, particularly under thermal conditions where velocity spread is prominent. We find that 4th-order pulses achieving up to a 87.9% improvement in contrast over rectangular pulses under realistic conditions, and while their peak performance at very low temperatures is comparable to that of Gaussian pulses, they demonstrate enhanced robustness against combined detuning and pulse area errors. These findings demonstrate that super-Gaussian pulse shaping is an effective method for enhancing the robustness of atom interferometers against errors induced by thermal motion.
Atom matterwave interferometry requires mirror and beam splitter pulses that are robust to inhomogeneities in field intensity, magnetic environment, atom velocity, and Zeeman substate. We present theoretical results which show that pulse shapes determined using quantum control methods can significantly improve interferometer performance by allowing broader atom distributions, larger interferometer areas, and higher contrast. We have applied gradient ascent pulse engineering (grape) to optimize the design of phase-modulated mirror pulses for a Mach-Zehnder light-pulse atom interferometer, with the aim of increasing fringe contrast when averaged over atoms with an experimentally relevant range of velocities, beam intensities, and Zeeman states. Pulses were found to be highly robust to variations in detuning and coupling strength and offer a clear improvement in robustness over the best established composite pulses. The peak mirror fidelity in a cloud of $\ensuremath{\sim}80\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{K}\phantom{\rule{4pt}{0ex}}^{85}\mathrm{Rb}$ atoms is predicted to be improved by a factor of 2 compared with standard rectangular $\ensuremath{\pi}$ pulses.
The mirrors and beamsplitters of atom interferometers often suffer from inhomogeneities in coupling strength and effective detuning because different atoms see different laser intensities, Zeeman and Doppler shifts and are in different Zeeman sub-states. This limits the fringe visibility for a simple interferometer, which falls off rapidly if extra mirrors are added, for example to increase the interferometer area. In practice, one usually therefore filters the atomic velocities/sub-states, thus losing signal, and/or restricting operation to small-area interferometers with low sensitivity. The problem is familiar in the field of NMR, where, instead of using simple pi or pi/2 pulses, the phase and potentially amplitude are modulated during the pulse so as to make the result robust to the inhomogeneities encountered. Despite the similarities with NMR systems, the numbers, correlations and performance measures for atom interferometry are different. We have used optimal control theory to obtain robust high fidelity mirror pulses for atom interferometry. Importantly, while the designs are found by computational simulation, we can validate them experimentally, with remarkably good agreement. We have addressed the optimization of individual mirror pulses, but the eventual aim is to optimize the interferometer as a whole: errors introduced in one pulse can be compensated at a later stage, for example. Our pulses yield high contrast without the need to filter the atomic sample and maintain this even in the case of extended pulse sequences, thus making it possible to achieve significantly larger interferometer areas than with simple pi pulses.
Abstract We present the theoretical design and experimental implementation of mirror and beamsplitter pulses that improve the fidelity of atom interferometry and increase its tolerance of systematic inhomogeneities. These pulses are designed using the GRAPE optimal control algorithm and demonstrated experimentally with a cold thermal sample of 85Rb atoms. We first show a stimulated Raman inversion pulse design that achieves a ground hyperfine state transfer efficiency of 99.8(3)%, compared with a conventional π pulse efficiency of 75(3)%. This inversion pulse is robust to variations in laser intensity and detuning, maintaining a transfer efficiency of 90% at detunings for which the π pulse fidelity is below 20%, and is thus suitable for large momentum transfer interferometers using thermal atoms or operating in non-ideal environments. We then extend our optimization to all components of a Mach–Zehnder atom interferometer sequence and show that with a highly inhomogeneous atomic sample the fringe visibility is increased threefold over that using conventional π and π/2 pulses.
Abstract Atom interferometers that employ atoms in superpositions of different electronic states are sensitive to any noise that affects these superposed states differently. Resilience to such noise results from using superpositions where the atomic states differ in momentum only, but implementation of such ‘state-symmetric’ diffraction can lead to population loss into unwanted states and restricts the atomic velocity acceptance of the interferometer. In this paper, by varying the laser intensities and phases as functions of time, we present optimized pulses designed for use in state-symmetric interferometers that overcome these restrictions. We extend this optimization to multi-pulse sequences designed to increase the interferometer area and demonstrate significant improvements in the fringe visibility compared with sequences of π/2 and π pulses. We discuss the limits on the temperature of the atomic source required for efficient atomic diffraction and show how optimized pulse sequences enable efficient diffraction with considerably warmer clouds, hence reducing the need for velocity selection and increasing the measurement signal-to-noise ratio.
Atom interferometers require both high efficiency and robust performance in their mirror pulses under experimental inhomogeneities. In this work, we demonstrated that quantum optimal control designed mirror pulse significantly enhance interferometer performance by using novel adaptive sliced structure. Using gradient ascent pulse engineering (GRAPE), optimized mirror pulse for a Mach-Zehnder light-pulse atom interferometer was designed by discretizing the control into non-uniform phase slices. This design broadened the tolerence to experimentally relevant variations in detuning [−Ω0,Ω0] and Rabi frequency [0.1×Ω0,1.9×Ω0] (Ω0=2π×25 kHz), while maintaining high transfer efficiency even when the response-time delays up to 1.6 μs. The optimized pulse was found to be robust to coupling inhomogeneity and velocity spread, offering a significant improvement in robustness over conventional pulse. The adaptive pulse slicing method provides a minimalist strategy that reduces experimental complexity while enhancing robustness and scalability, offering an innovative scheme for quantum optimal control in high precision atom interferometry.