Performing interferometry in an optical lattice formed by standing waves of light offers potential advantages over its free-space equivalents since the atoms can be confined and manipulated by the optical potential. We demonstrate such an interferometer in a one-dimensional lattice and show the ability to control the atoms by imaging and reconstructing the wave function at many stages during its cycle. An acceleration signal is applied, and the resulting performance is seen to be close to the optimum possible for the time-space area enclosed according to quantum theory. Our methodology of machine design enables the sensor to be reconfigurable on the fly, and when scaled up, offers the potential to make state-of-the art inertial and gravitational sensors that will have a wide range of potential applications. Published by the American Physical Society 2024
Performing interferometry in an optical lattice formed by standing waves of light offers potential advantages over its free-space equivalents since the atoms can be confined and manipulated by the optical potential. We demonstrate such an interferometer in a one-dimensional lattice and show the ability to control the atoms by imaging and reconstructing the wave function at many stages during its cycle. An acceleration signal is applied, and the resulting performance is seen to be close to the optimum possible for the time-space area enclosed according to quantum theory. Our methodology of machine design enables the sensor to be reconfigurable on the fly, and when scaled up, offers the potential to make state-of-the art inertial and gravitational sensors that will have a wide range of potential applications. Published by the American Physical Society 2024
We theoretically study a new approach to matter-wave interferometer that utilizes ultracold atoms confined in an optical lattice. Through patterned phase modulation of the lattice, the matter wave is split, mirrored, and recombined, resulting in sensitivity to an applied inertial signal as was recently demonstrated experimentally in [LeDesma et al., arXiv:2305.17603 (2023)]. Compared to free-space equivalents, this “shaken lattice” interferometer has the advantage that atoms remain always supported against external forces and perturbations and that by applying different shaking sequences the device could be in principle made sensitive to different signals (inertial, gravitational, etc...) on the fly. In this work, we give a brief overview of this sensing platform and its working principles.
The creation of a 1D matter-wave interferometer can be achieved by utilizing ultracold atoms loaded into an optical lattice. By shaking the lattice via either phase or frequency modulation, the traditional steps of interferometry- effectively splitting, propagating, reflecting, again propagating and then recombining the atomic wavefunction- can be implemented, allowing for the sensing of inertial signals. This approach is interesting, since the atoms can be supported against external forces and perturbations, and the system can be completely reconfigurable on-the-fly for a new design goal. We report on experimental results in which atoms are cooled into a dipole trap and subsequently loaded into an optical lattice. Shaking protocols for obtaining interferometry steps are derived via machine learning and quantum optimal control methods. We report experimental progress in realizing a shaken lattice interferometer and its sensitivity to an applied acceleration signal along with the possibility of tailoring the signal to specific scenarios. Additionally, closed loop learning from the experiment to improve signal sensitivity is explored and demonstrated.
The creation of a matter-wave interferometer can be achieved by loading Bose-Einstein condensed atoms into an optical lattice. By shaking the lattice via either phase or frequency modulation, the traditional steps of interferometry; splitting, propagating, reflecting, again propagating and then recombining the atomic wavefunction, can be implemented, allowing for the sensing of broad range of inertial signals. This approach is interesting, since the atoms can be supported against external forces and perturbations, and the system can be completely reconfigurable on-the-fly for a new design goal. We report on theoretical and experimental results in which atoms are cooled to degeneracy in a dipole trap and subsequently loaded into a multidimensional optical lattice. Shaking protocols for obtaining interferometry steps are derived via machine-design approaches consisting of machine learning and quantum optimal control. Experimental confirmation of the designed operation of a two-dimensional vector accelerometer is shown and its performance to applied accelerations measured. Both the direction and magnitude of the applied signal is varied and validation of both scenarios presented.
Since the first demonstrations in 1991, atom interferometry has been a burgeoning field of research. The work done in this field is motivated by the potential sensitivity improvements that atom-based devices can have over the current state-of-the-art light- and MEMS-based devices. This dissertation presents a new and unique approach to atom interferometry in that we perform the basic interferometric sequence of splitting, propagation, reflection, reverse-propagation, and recombination with atoms trapped in a phase-modulated (shaken) optical lattice. In both simulation and experiment we demonstrate a one-dimensional shaken lattice interferometer configured as an accelerometer. The interferometry sequence is developed through the use of learning and optimal control algorithms that allow us to implement the desired state-to-state transformations and perform the desired operations, e.g. splitting and recombination of the atoms trapped in the lattice. This device has a sensitivity that scales as the square of the interrogation time and an ability to distinguish both the magnitude and sign of an applied acceleration signal. Furthermore we show that we can tailor the transfer function of the interferometer to be sensitive to a signal of interest, e.g. an AC signal of a given frequency. Finally, we explore the analytics of shaken lattice interferometry and offer some suggestions as to the future of this new technology.
Programming a quantum device describes the usage of quantum logic gates, agnostic of hardware specifics, to perform a sequence of operations with (typically) a computing or sensing task in mind. Such programs have been executed on gate-based quantum computers, which despite their noisy character, have shown the ability to optimize metrological functions, for example in the generation of spin squeezing and optimization of quantum Fisher information for signals manifesting as spin rotations in a quantum register. However, the qubits of these programmable quantum sensors are tightly spatially confined and therefore suboptimal for enclosing the kinds of large spacetime areas required for performing inertial sensing. In this work, we derive a set of quantum logic gates for a cold atom optical lattice interferometer that manipulates the momentum of atoms. Here, the operations are framed in terms of single qubit operations and mappings between qubit subspaces with internal levels given by the Bloch (crystal) eigenstates of the lattice. We describe how the quantum optimal control method of direct collocation is well suited for obtaining modulation waveforms of an optical lattice to achieve these operations in existing experimental setups.
Bloch oscillations of atoms in optical lattices are a powerful technique that can dramatically boost the sensitivity of atom interferometers to a wide range of signals by large momentum transfer. To leverage this method to its full potential, an accurate theoretical description of losses and phases is required, going beyond existing treatments. Here, we present a comprehensive theoretical framework for Bloch-oscillation-enhanced atom interferometry and verify its accuracy through comparison with a numerical solution of the Schrödinger equation. Our approach establishes design criteria to reach the fundamental efficiency and accuracy limits of large momentum transfer using Bloch oscillations and allows us, in a broader context, to define the fundamental efficiency limit of the transport of neutral atoms using optical lattices. We compare these limits to the capabilities of current state-of-the-art experiments and make projections for the next generation of quantum sensors. Published by the American Physical Society 2024