Research project B01 – SFB 1227 DQ-mat – Leibniz University Hannover

Introduction

Atom interferometers belong to today’s most precise sensors with broad applications for navigation, geodesy, time keeping as well as fundamental research. Typically, they are operated with uncorrelated particles, resulting in a fundamental limitation of the achievable sensitivity – the standard quantum limit (SQL). While the SQL allows improving the sensitivity by increasing the particle number, we have shown in the second funding period in collaboration with B07 (delocalised states) that quantum density fluctuations place a limit to this improvement, leading to an optimal atom number and a corresponding sensitivity limit, the density quantum limit (DQL). Both sensitivity limits can only be overcome by employing entangled particles as an input for new types of non-classical interferometers. However, up to now, only few proof-of-principle experiments have actually succeeded to exploit entangled sources of atoms for interferometric measurements. In this project, we advance our method from demonstration experiments to a valuable source for a future generation of highest-sensitivity atomic sensors.

Results

Within the second funding period, we have achieved important goals in this direction. We decreased the generation time of Rb Bose-Einstein condensates (BECs) to a world-record of 500 ms by employing dynamically shapeable optical potentials. Short BEC generation times are equally important for interfer- ometry with high duty cycles and for performing quantum state tomography for entangled many-body quantum states. We improved our detection system for single-particle resolved counting of up to 700 atoms. The novel detection has enabled us to perform a first single-atom resolved state tomography with a coherent spin state, that was generated on the Rb clock transition. Finally, we have just reached a ma- jor milestone in the lab by analysing a two-mode squeezed vacuum state with single-particle resolution.

The two-mode squeezed state is characterised by the generation of particle pairs, and prominent odd- even oscillations in the total atom number, all of which are now directly observable in our experiments. The two-mode squeezed state is a preferable input state for entanglement-enhanced interferometry, as we have shown within A02 (non-Gaussian atomic states). Here, we demonstrated the operation of a Ramsey sequence on the Rb clock transition beyond the SQL with long Ramsey times of up to 7 ms, solely limited by the available spatial region. Based on the development of a high-performance Raman laser system in collaboration with B07, the clock sequence was extended to a full atom interferomet- ric gravimeter. We have first results for an absolute gravimeter that enables a measurement of the gravitational acceleration with a resolution beyond the SQL, for the first time worldwide.

Publications

Showing results 1 - 9 out of 9

Feldmann P, Anders F, Idel A, Schubert C, Schlippert D, Santos L et al. Optimal squeezing for high-precision atom interferometers. 2023 Nov 17. Epub 2023 Nov 17. doi: 10.48550/arXiv.2311.10241

Hetzel M, Pezzè L, Pür C, Quensen M, Hüper A, Geng J et al. Tomography of a Number-Resolving Detector by Reconstruction of an Atomic Many-Body Quantum State. Physical review letters. 2023 Dec 26;131(26):260601. doi: 10.48550/arXiv.2207.01270, 10.1103/PhysRevLett.131.260601

Pür C, Hetzel M, Quensen M, Hüper A, Geng J, Kruse J et al. Rapid generation and number-resolved detection of spinor Rubidium Bose-Einstein condensates. Physical Review A. 2023 Mar 6;107(3):033303. doi: 10.48550/arXiv.2301.08172, 10.1103/PhysRevA.107.033303

Vitagliano G, Fadel M, Apellaniz I, Kleinmann M, Lücke B, Klempt C et al. Number-phase uncertainty relations and bipartite entanglement detection in spin ensembles. Quantum. 2023 Feb 9;7:914. Epub 2021 Apr 12. doi: 10.48550/arXiv.2104.05663, 10.22331/q-2023-02-09-914

Hueper A, Puer C, Hetzel M, Geng J, Peise J, Kruse I et al. Number-resolved preparation of mesoscopic atomic ensembles. New journal of physics. 2020 Dec 13;23(11):113046. doi: 10.1088/1367-2630/abd058

Kristensen MA, Christensen MB, Gajdacz M, Iglicki M, Pawłowski K, Klempt C et al. Observation of Atom Number Fluctuations in a Bose-Einstein Condensate. Physical Review Letters. 2019 Apr 26;122(16):163601. Epub 2019 Apr 22. doi: 10.48550/arXiv.1812.03064, 10.1103/PhysRevLett.122.163601

Pezzè L, Gessner M, Feldmann P, Klempt C, Santos L, Smerzi A. Heralded Generation of Macroscopic Superposition States in a Spinor Bose-Einstein Condensate. Physical Review Letters. 2019 Dec 31;123(26):260403. Epub 2019 Dec 27. doi: 10.48550/arXiv.1712.03864, 10.1103/PhysRevLett.123.260403

Kristensen MA, Gajdacz M, Pedersen PL, Klempt C, Sherson JF, Arlt JJ et al. Sub-atom shot noise Faraday imaging of ultracold atom clouds. Journal of Physics B: Atomic, Molecular and Optical Physics. 2017 Jan 17;50(3):034004. doi: 10.1088/1361-6455/50/3/034004

Gajdacz M, Hilliard AJ, Kristensen MA, Pedersen PL, Klempt C, Arlt JJ et al. Preparation of Ultracold Atom Clouds at the Shot Noise Level. Physical Review Letters. 2016 Aug 12;117(7):073604. doi: 10.1103/PhysRevLett.117.073604, 10.15488/3592

All publications of the Collaborative Research Centre

Overview