Observing spin-squeezed states under spin-exchange collisions for a second

Abstract

Using the platform of a trapped-atom clock on a chip, we have generated spin-squeezed states with up to 8.1(9) dB of metrological squeezing in a cloud of 2 × 10 4 ultracold alkali atoms by quantum nondemolition (QND) measurement in a fiber Fabry-Perot microcavity. Observing the time evolution of the squeezed state on unprecedented timescales of more than one second reveals a surprising measurement amplification effect in the final measurement of the spin state. It results from a subtle interplay between the spin dynamics of interacting indistinguishable particles and energy-dependent cavity coupling and leads to an increased cavity shift per spin, and thus to a higher signal per photon read out. Metrological spin squeezing is preserved for 1 s. Both results open up encouraging perspectives for squeezing-enhanced atomic clocks in a metrologically relevant stability regime.

Time-Reversal-Based Quantum Metrology with Many-Body Entangled States

“…Over the last two decades, substantial effort has been devoted towards the design of protocols and the engineering of quantum states that enable the operation of atomic sensors beyond the Standard Quantum Limit (SQL) (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). The SQL arises from the discreteness of outcomes in the quantum measurement process, i.e.…”

“…Blue data: BEC experiments(4)(5)(6)(7)15). Red data: Thermal atoms experiments(2,3,8,9,11,14). Black data: Ions(10,20).…”

Utilizing machine learning to improve the precision of fluorescence imaging of cavity-generated spin squeezed states

“…Absorption imaging, especially high intensity imaging, requires careful calibration to accurately count atoms [17,18]. A ML approach could circumvent traditional calibration techniques to convert pixel-by-pixel intensity changes to atom numbers in spin squeezing experiments [19].…”

Collective Spin-Light and Light-Mediated Spin-Spin Interactions in an Optical Cavity

“…This fundamental contrast reduction for phase-sensitive measurements affects the performance of spin squeezed atomic clocks [24,25,83,107] and other interferencebased atomic sensors [27,47,108,109].…”