Spatially Split Spin-Squeezed Bose-Einstein Condensates for Multiparameter Metrology and Clock Interferometry

Speaker: Michał Lipka

Affiliation: University of Basel

Abstract: We present a versatile atom-chip platform for multiparameter quantum sensing based on a two component 87Rb Bose–Einstein condensate. Our setup enables the generation of collective spin-squeezed states via one-axis twisting dynamics, followed by the coherent spatial splitting of the condensate into multiple individually addressable clouds. This splitting process successfully preserves both the internal (intra-cloud) and distributed (inter-cloud) many-body entanglement. Recently, we utilized this capability to create an array of up to three entangled atomic sensors, each constituing several hundreds of atoms. By optimizing the measurement protocol to fully exploit the inter-sensor entanglement, we demonstrated the simultaneous estimation of multiple local parameters, achieving quantum gains of up to 3.6 dB beyond the standard quantum limit [1].
These results establish mesoscopic condensates on atom chips as a powerful experimental testbed for multiparameter quantum metrology and fundamental studies of steering and non-locality [2, 3]. Further more, our architecture holds great promise for proof of principle studies in quantum clock interferometry. The internal degree of freedom of each split cloud acts as a local clock measuring the phase evolution between the 2 hyperfine levels. Together with the ability to split, independently manipulate, and co herently recombine the entangled ensembles, it provides the essential tools for future studies exploring entanglement-enhanced clock interferometry, which has been proposed as a tool for measuring General Relativity effects in a laboratory setting [4, 5].
In this contribution, we will detail our recent multiparameter sensing results and outline the roadmap for future experiments in clock interferometry with our platform.
FIG. 1: (a) Idea of the multiparameter sensing with a spatial array of entangled atomic clouds on an
atomic chip. The collective spin of each ensemble senses a different parameter which may correspond to a value of a field at the cloud’s location and is imprinted as a spin rotation. Utilizing inter- and intra-sensor entanglement enhances the overall sensitivity beyond classical limits. (b) Idea of the clock interferometry. A squeezed or coherent state would be generated on the atomic chip platform and subsequenetly split into 2 spatially separate clouds. Each cloud maintains an internal hyperfine degree of freedom acting as a clock. The clouds can be brought back together with Stern-Gerlach type magnetic field control and interfered upon measurement.

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