TY - BOOK

T1 - Matter-wave dynamics in time-averaged optical potentials with tunable interactions

AU - Herbst, Alexander

PY - 2024

Y1 - 2024

N2 - Atom interferometers have emerged as a pivotal tool for accurate measurements of inertial effects and are used as a versatile instrument in both fundamental physics investigations and various applications. In particular, they have excelled in quantum tests of the Universality of Free Fall and are expected to be instrumental in the development of future gravitational wave detectors and in the search for dark matter. However, these experiments impose stringent requirements for a large atomic flux in combination with ultra-low expansion rates to enhance their sensitivity and to restrict systematic effects. In this thesis, time-averaged optical potentials in conjunction with tunable interactions are used to rapidly create collimated K-39 Bose-Einstein condensates. Combining these two methods for the first time allows to reach an unprecedented evaporation duration of only 170 ms with an atom number of more than 60000 particles, well-suited for interferometry applications. By individually tailoring trap frequencies and interaction strength it is also demonstrated how the resulting flux of more than 300000 particles/s can be maintained when transitioning to large condensates of more than 570000 atoms within less than 2 s of evaporative cooling. These advancements enable the preparation of suitable interferometry input states well within the actual interferometer time, thereby enabling dead-time free measurements with superior sensitivity. Moreover, the same techniques are used to implement a matter-wave lens, directly applicable in the optical-dipole trap without necessitating extended free-fall times. By incorporating tunable interactions, a collimation scheme previously developed with Rb-87 is enhanced, yielding measured energies as low as 340 pK in one direction. Dedicated theory simulations are used to arrive at an intricate understanding of the related dynamics, allowing to extrapolate a 2D ballistic expansion energy of 438 pK for the performed experiment. Based on these results an extended multi-stage collimation scheme is proposed which will reduce the expansion energy to below 20 pK in three dimensions, far surpassing the requirements of current 10 m baseline devices such as the Hannover VLBAI facility. These results pave the way to realize state-of-the-art matter-wave collimation in compact or lab-based apparatuses, independent of the unique features of long-baseline devices or micro-gravity environments. Ultimately, the various implemented methods will allow to perform interferometry experiments in trapped configurations and enable squeezing-enhanced interferometry schemes for measurements below the standard quantum limit.

AB - Atom interferometers have emerged as a pivotal tool for accurate measurements of inertial effects and are used as a versatile instrument in both fundamental physics investigations and various applications. In particular, they have excelled in quantum tests of the Universality of Free Fall and are expected to be instrumental in the development of future gravitational wave detectors and in the search for dark matter. However, these experiments impose stringent requirements for a large atomic flux in combination with ultra-low expansion rates to enhance their sensitivity and to restrict systematic effects. In this thesis, time-averaged optical potentials in conjunction with tunable interactions are used to rapidly create collimated K-39 Bose-Einstein condensates. Combining these two methods for the first time allows to reach an unprecedented evaporation duration of only 170 ms with an atom number of more than 60000 particles, well-suited for interferometry applications. By individually tailoring trap frequencies and interaction strength it is also demonstrated how the resulting flux of more than 300000 particles/s can be maintained when transitioning to large condensates of more than 570000 atoms within less than 2 s of evaporative cooling. These advancements enable the preparation of suitable interferometry input states well within the actual interferometer time, thereby enabling dead-time free measurements with superior sensitivity. Moreover, the same techniques are used to implement a matter-wave lens, directly applicable in the optical-dipole trap without necessitating extended free-fall times. By incorporating tunable interactions, a collimation scheme previously developed with Rb-87 is enhanced, yielding measured energies as low as 340 pK in one direction. Dedicated theory simulations are used to arrive at an intricate understanding of the related dynamics, allowing to extrapolate a 2D ballistic expansion energy of 438 pK for the performed experiment. Based on these results an extended multi-stage collimation scheme is proposed which will reduce the expansion energy to below 20 pK in three dimensions, far surpassing the requirements of current 10 m baseline devices such as the Hannover VLBAI facility. These results pave the way to realize state-of-the-art matter-wave collimation in compact or lab-based apparatuses, independent of the unique features of long-baseline devices or micro-gravity environments. Ultimately, the various implemented methods will allow to perform interferometry experiments in trapped configurations and enable squeezing-enhanced interferometry schemes for measurements below the standard quantum limit.

U2 - 10.15488/17570

DO - 10.15488/17570

M3 - Doctoral thesis

CY - Hannover

ER -