Continuously trapped matter-wave interferometry in magic Floquet-Bloch band structures
Xiao Chai, Eber Nolasco-Martinez, Xuanwei Liang, Jeremy L. Tanlimco, Ethan Q. Simmons, Eric Zhu, Roshan Sajjad, Hèctor Mas, S. Nicole Halawani, Alec Cao, David Weld
Trapped matter-wave interferometry offers the promise of compact high-precision local force sensing. However, noise in the trap itself can introduce new systematic errors which are absent in traditional free-fall interferometers. We describe and demonstrate an intrinsically noise-tolerant Floquet-engineered platform for continuously trapped atom interferometry. A non-interacting degenerate quantum gas undergoes position-space Bloch oscillations through an amplitude-modulated optical lattice, whose resulting Floquet-Bloch band structure includes Landau-Zener beamsplitters and Bragg mirrors, forming the components of a Mach-Zehnder interferometric force sensor. We identify, realize, and experimentally characterize magic band structures, analogous to the magic wavelengths employed in optical lattice clocks, for which the interferometric phase is insensitive to lattice intensity noise. We leverage the intrinsic programmability of the Floquet band synthesis approach to demonstrate a variety of interferometer structures, highlighting the potential of this technique for quantum force sensors which are tunable, compact, simple, and robust.
Trapped matter-wave interferometry offers the promise of compact high-precision local force sensing. However, noise in the trap itself can introduce new systematic errors which are absent in traditional free-fall interferometers. We describe and demonstrate an intrinsically noise-tolerant Floquet-engineered platform for continuously trapped atom interferometry. A non-interacting degenerate quantum gas undergoes position-space Bloch oscillations through an amplitude-modulated optical lattice, whose resulting Floquet-Bloch band structure includes Landau-Zener beamsplitters and Bragg mirrors, forming the components of a Mach-Zehnder interferometric force sensor. We identify, realize, and experimentally characterize magic band structures, analogous to the magic wavelengths employed in optical lattice clocks, for which the interferometric phase is insensitive to lattice intensity noise. We leverage the intrinsic programmability of the Floquet band synthesis approach to demonstrate a variety of interferometer structures, highlighting the potential of this technique for quantum force sensors which are tunable, compact, simple, and robust.
Trapped matter-wave interferometry offers the promise of compact high-precision local force sensing. However, noise in the trap itself can introduce new systematic errors which are absent in traditional free-fall interferometers. We describe and demonstrate an intrinsically noise-tolerant Floquet-engineered platform for continuously trapped atom interferometry. A non-interacting degenerate quantum gas undergoes position-space Bloch oscillations through an amplitude-modulated optical lattice, whose resulting Floquet-Bloch band structure includes Landau-Zener beamsplitters and Bragg mirrors, forming the components of a Mach-Zehnder interferometric force sensor. We identify, realize, and experimentally characterize magic band structures, analogous to the magic wavelengths employed in optical lattice clocks, for which the interferometric phase is insensitive to lattice intensity noise. We leverage the intrinsic programmability of the Floquet band synthesis approach to demonstrate a variety of interferometer structures, highlighting the potential of this technique for quantum force sensors which are tunable, compact, simple, and robust.
Atom interferometers exploit the wave nature of matter to measure inertial forces with high precision, but conventional light-pulse implementations typically require large free-fall distances and complex optical systems. Bloch-band interferometry offers an alternative architecture in which atoms remain confined within an optical lattice and interferometric operations are implemented through controlled transitions between Bloch bands. This thesis investigates Bloch-band interferometry with particular emphasis on robustness to phase decoherence and operation in the deep-lattice regime. The work begins with multi-well models that provide intuition for tunneling, interference, and phase coherence. Phase scrambling was introduced to model loss of coherence, demonstrating that interference contrast is reduced but not eliminated. These insights motivated a full momentum-space simulation of a Bloch-band Michelson interferometer, including splitting, transport, reflection, and recombination. Acceleration scans with site-to-site phase randomness showed that interferometric fringes and sensitivity persist even with reduced coherence. Building on this robustness, Bloch-band interferometry was extended to a deep optical lattice with depth of 27 times the recoil energy. Higher Bloch bands were used to define interferometric pathways, and machine-learned shaking functions were implemented to realize beamsplitter and mirror operations. The resulting deep-lattice interferometer exhibits acceleration-dependent population fringes and measurable sensitivity. To our knowledge, this work presents the first exploration of Bloch-band interferometry in the deep-lattice regime and demonstrates the first realization of a deep-lattice Bloch-band interferometer for inertial sensing. These results suggest that Bloch-band interferometry can remain operational in regimes approaching the insulating limit, providing a potential route toward compact and robust quantum inertial sensors.
Microgravity environments provide unique opportunities for ultracold-atom experiments by enabling long interrogation times and reduced acceleration-induced dynamics. However, their realization has largely been restricted to specialized facilities such as drop towers, sounding rockets, and space-based laboratories. Here we realize synthetic microgravity for quantum degenerate gases using optically engineered force landscapes that compensate Earth's gravity to the milli-g level while maintaining continuous confinement of the atomic ensemble. These force landscapes are generated by dynamically painted optical dipole potentials and calibrated in situ through Bloch oscillations in a vertical optical lattice, enabling precise control of the residual acceleration. We use this capability to demonstrate matter-wave beam splitting with arm separations of several hundred microns. We further implement a Bloch-band atom interferometer in which interaction-induced dephasing is strongly suppressed through controlled three-dimensional expansion in the synthetic microgravity potential. This reduction of mean-field effects restores near-N scaling of interferometric sensitivity for large quantum degenerate ensembles. Our results establish a versatile platform for realizing synthetic microgravity with trapped quantum gases in terrestrial laboratories, bringing the advantages of microgravity experiments to continuously operating systems and opening new opportunities for quantum sensing, matter-wave interferometry, and precision measurements.
Atom interferometers measure the relative phase shifts between coherent matter-wave paths that arise from interactions with external fields or inertial forces. Due to their exceptional phase sensitivity, atom interferometers became an essential tool for precision measurements and fundamental physics experiments, finding applications in geodesy, gravimetry, and inertial navigation. However, their measurement precision is limited by quantum projection noise, which arises from the Heisenberg uncertainty principle, preventing the measurement of atomic states with absolute precision. The generation of entanglement between the atoms offers a path to surpass this so-called standard quantum limit, thereby enhancing the interferometer’s phase sensitivity beyond classical measurement bounds. This thesis reports on the development of an atom interferometer experiment designed to realize cavity-mediated, squeezed Mach-Zehnder-type interferometry with ultra-cold 87Rb atoms. The experiment combines cavity-aided spin-squeezing with cavity-mediated Mach-Zehnder interferometry to demonstrate entanglement-enhanced phase sensitivity. The experiment is centered on a triangular optical cavity that mediates all relevant atom-light interactions. The cavity provides optical trapping, spin-squeezing, and Raman beam-splitter operations, enabling to perform interferometry on a continuously trapped atomic ensemble. The thesis elaborates on the fundamental theoretical framework, the cavity design, and the full optical setup, including the detailed configuration of the developed laser stabilization methods. Experimentally, continuous loading methods were explored, resulting in an accumulation of up to 4 × 106 atoms in the dipole trap within a cycle time of 500 ms. The AC Stark shift compensation method developed for continuous loading was further applied for in-trap cooling to 10 µK, and optical pumping for efficient atomic state preparation. Coherent state control was verified via observation of microwave-driven Rabi oscillations, and used to characterize atom-cavity coupling. These presented results establish the experimental groundwork for the future development of cavity-mediated, entanglement-enhanced Mach-Zehnder-type atom interferometry.
Optical clocks and atom interferometers provide complementary ways to measure time, motion and gravity. Combining these capabilities requires matter-wave beam splitters that manipulate different clock states in the same way, so that optical internal energy becomes a controlled degree of freedom rather than a source of systematic phase shifts. Here we realized a dual matter-wave interferometer operating simultaneously on the two states of the 88Sr optical clock transition, 1S0 and 3P0. The interferometer is driven by Bragg pulses at the 813 nm magic wavelength, for which the two clock states experience the same optical coupling strength. This realizes a common matter-wave beam splitter for atoms whose internal energies differ by an optical excitation. With a sensitivity of 30 mrad, our measurement is consistent with a zero differential phase shift between the two clock-state Mach-Zehnder interferometers, translating to an absence of state-dependent acceleration in free fall at the level of 10−5. We further used the same interferometer to measure state-dependent optical dipole forces and determine a tune-out wavelength of the metastable 3P0 state to be 478.95(8) nm. These results establish magic-wavelength clock-state interferometry as a platform for differential force sensing, excited-state polarizability metrology and future quantum-clock tests of gravity.
Abstract The coherent manipulation of a quantum wave is at the core of quantum sensing. For instance, atom interferometers require linear splitting and recombination processes to map the accumulated phase shift into a measurable population signal. Although Bose Einstein condensates (BECs) are the archetype of coherent matter waves, their manipulation between trapped spatial modes has been limited by the strong interparticle collisions. Here, we overcome this problem by using BECs with tunable interaction trapped in an innovative array of double-well potentials and exploiting quantum tunneling to realize linear beam splitting. We operate several Mach-Zehnder interferometers in parallel, canceling common-mode potential instabilities by a differential analysis, thus demonstrating a trapped-atom gradiometer. Furthermore, by applying a spin-echo protocol, we suppress additional decoherence sources and approach unprecedented coherence times of one second. Our interferometer will find applications in precision measurements of forces with a high spatial resolution and in linear manipulation of quantum entangled states for sensing with sub shot-noise sensitivity.