Apparatus for quantum-mixture research in microgravity

Nat. Commun. 17, 7573 (2026) · DOI: 10.1038/s41467-026-75968-9 · arXiv: 2508.20820

License: CC BY 4.0.

Abstract

Experiments with ultracold quantum gases are a rapidly advancing research field with many applications in fundamental physics and quantum technology. Here, we report on a high-flux generation of Bose-Einstein condensate mixtures of 41 K and 87 Rb, using a fully integrated sounding rocket setup. We compare the release and the free expansion of the quantum mixtures obtained with the apparatus placed on ground or in free fall in an Einstein-Elevator. The release dynamics are governed by the intra- and interspecies interactions as well as the decaying magnetic field during the release. The latter can be minimized by a dedicated switch-off protocol of the trap generating currents where an exact model enabled us to characterize the interaction effects. Our results establish a new benchmark for generating ultracold mixtures on mobile platforms, with direct relevance for future experiments on interacting quantum gases and tests of the equivalence principle in space.

Figures

39 panels with data across 5 figures. Each panel page shows the plot, its columns and its files; each data.csv begins with a header naming the paper, the panel, the source, the license and the provenance route.

Fig. 1

Illustrative figure, no extractable data. Shown in the paper PDF.

Fig. 2

• panel (1): Condensed number of atoms of $^{41}$K ($\times 10^4$) against condensed number of atoms of $^{87}$Rb ($\times 10^5$) for 20 BEC mixtures prepared on ground with different ratios. Rings 1 to 4 mark the configurations whose absorption images the print shows beside the plot; the images and the inset are not part of this panel. data.csv
• panel (1-inset): Inset of the figure: typical loading curves of the magnetic traps, atom numbers against MOT loading time in ms, $^{87}$Rb (red, left axis, $\times 10^6$) and $^{41}$K (blue, right axis, untitled in the print), points with smooth curves. The Start Rb MOT arrow and the grey shading for longer loading times are not drawn. data.csv

Fig. 3

• panel (1): Atoms in the BEC fraction against preparation time in s (log axes) for this work and other experiments, $^{87}$Rb in red and $^{41}$K in blue, each experiment labelled and its two species joined by a black line. Grey dashed lines mark constant atomic flux of $10^2$ to $10^5$ s$^{-1}$. BECCAL and STE-QUEST are required capabilities, drawn faded in the print. data.csv

Fig. 4

• panel (b): Differential release velocity $\Delta v$ (m/s) between $^{41}$K and $^{87}$Rb against the delay $\Delta t$ (ms) between switching off the atom chip and the external coil, measured on ground (black circles) and in microgravity (magenta triangles) with error bars. Dashed lines are the simulated release, shaded for a 5% change of the decay constants; the dotted line is a weak trap in microgravity. data.csv
• panel (b-inset): Inset of panel (b): the same differential release velocities $\Delta v$ (m/s) and simulated curves around the zero crossing, $\Delta t$ from 0.06 to 0.10 ms. The dashed box marking this region in panel (b) is not drawn there. data.csv

Fig. 5

• panel (a-1): Panel (a), top: projected 1D line density $P_Y$ ($\mu$m$^{-1}$) against $Y_{CAM}$ ($\mu$m) of the $^{41}$K and $^{87}$Rb mixture after free expansion on ground at $\varphi = 0.0^\circ$. Rb data in red, K data in cyan, Gross-Pitaevskii simulations with a transient magnetic trap switch-off in black (dash-dot Rb, dashed K). The absorption image is not part of this panel. data.csv
• panel (a-2): Panel (a), right: projected 1D line density $P_X$ ($\mu$m$^{-1}$), horizontal, against $X_{CAM}$ ($\mu$m), vertical and increasing downward as printed, on ground at $\varphi = 0.0^\circ$. Rb data in red, K data in cyan, simulations with a transient magnetic trap switch-off in black (dash-dot Rb, dashed K). data.csv
• panel (a-3): Panel (a), image: $^{87}$Rb column density on ground at $\varphi = 0.0^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White solid lines: contours of the simulated Rb density with a transient trap switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (a-4): Panel (a), image: $^{41}$K column density on ground at $\varphi = 0.0^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White dashed lines: contours of the simulated K density with a transient trap switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (b-1): Panel (b), top: projected 1D line density $P_Y$ ($\mu$m$^{-1}$) against $Y_{CAM}$ ($\mu$m) of the $^{41}$K and $^{87}$Rb mixture after free expansion on ground at $\varphi = 30.9^\circ$. Rb data in red, K data in cyan, Gross-Pitaevskii simulations with a transient magnetic trap switch-off in black (dash-dot Rb, dashed K). The absorption image is not part of this panel. data.csv
• panel (b-2): Panel (b), right: projected 1D line density $P_X$ ($\mu$m$^{-1}$), horizontal, against $X_{CAM}$ ($\mu$m), vertical and increasing downward as printed, on ground at $\varphi = 30.9^\circ$. Rb data in red, K data in cyan, simulations with a transient magnetic trap switch-off in black (dash-dot Rb, dashed K). data.csv
• panel (b-3): Panel (b), image: $^{87}$Rb column density on ground at $\varphi = 30.9^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White solid lines: contours of the simulated Rb density with a transient trap switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (b-4): Panel (b), image: $^{41}$K column density on ground at $\varphi = 30.9^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White dashed lines: contours of the simulated K density with a transient trap switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (c-1): Panel (c), top: projected 1D line density $P_Y$ ($\mu$m$^{-1}$) against $Y_{CAM}$ ($\mu$m) of the $^{41}$K and $^{87}$Rb mixture after free expansion on ground at $\varphi = 60.6^\circ$. Rb data in red, K data in cyan, Gross-Pitaevskii simulations with a transient magnetic trap switch-off in black (dash-dot Rb, dashed K). The absorption image is not part of this panel. data.csv
• panel (c-2): Panel (c), right: projected 1D line density $P_X$ ($\mu$m$^{-1}$), horizontal, against $X_{CAM}$ ($\mu$m), vertical and increasing downward as printed, on ground at $\varphi = 60.6^\circ$. Rb data in red, K data in cyan, simulations with a transient magnetic trap switch-off in black (dash-dot Rb, dashed K). data.csv
• panel (c-3): Panel (c), image: $^{87}$Rb column density on ground at $\varphi = 60.6^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White solid lines: contours of the simulated Rb density with a transient trap switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (c-4): Panel (c), image: $^{41}$K column density on ground at $\varphi = 60.6^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White dashed lines: contours of the simulated K density with a transient trap switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (d-1): Panel (d), top: projected 1D line density $P_Y$ ($\mu$m$^{-1}$) against $Y_{CAM}$ ($\mu$m) of the $^{41}$K and $^{87}$Rb mixture after free expansion in microgravity. Rb data in red, K data in cyan, Gross-Pitaevskii simulations with a transient magnetic trap switch-off in black (dash-dot Rb, dashed K). The absorption image is not part of this panel. data.csv
• panel (d-2): Panel (d), right: projected 1D line density $P_X$ ($\mu$m$^{-1}$), horizontal, against $X_{CAM}$ ($\mu$m), vertical and increasing downward as printed, in microgravity. Rb data in red, K data in cyan, simulations with a transient magnetic trap switch-off in black (dash-dot Rb, dashed K). data.csv
• panel (d-3): Panel (d), image: $^{87}$Rb column density in microgravity, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White solid lines: contours of the simulated Rb density with a transient trap switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (d-4): Panel (d), image: $^{41}$K column density in microgravity, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White dashed lines: contours of the simulated K density with a transient trap switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (e-1): Panel (e), top: projected 1D line density $P_Y$ ($\mu$m$^{-1}$) against $Y_{CAM}$ ($\mu$m) of the $^{41}$K and $^{87}$Rb mixture after free expansion on ground at $\varphi = 0.0^\circ$. Rb data in red, K data in cyan, Gross-Pitaevskii simulations with an instantaneous switch-off in black (dash-dot Rb, dashed K). The absorption image is not part of this panel. data.csv
• panel (e-2): Panel (e), right: projected 1D line density $P_X$ ($\mu$m$^{-1}$), horizontal, against $X_{CAM}$ ($\mu$m), vertical and increasing downward as printed, on ground at $\varphi = 0.0^\circ$. Rb data in red, K data in cyan, simulations with an instantaneous switch-off in black (dash-dot Rb, dashed K). data.csv
• panel (e-3): Panel (e), image: $^{87}$Rb column density on ground at $\varphi = 0.0^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White solid lines: contours of the simulated Rb density with an instantaneous switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (e-4): Panel (e), image: $^{41}$K column density on ground at $\varphi = 0.0^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White dashed lines: contours of the simulated K density with an instantaneous switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (f-1): Panel (f), top: projected 1D line density $P_Y$ ($\mu$m$^{-1}$) against $Y_{CAM}$ ($\mu$m) of the $^{41}$K and $^{87}$Rb mixture after free expansion on ground at $\varphi = 30.9^\circ$. Rb data in red, K data in cyan, Gross-Pitaevskii simulations with an instantaneous switch-off in black (dash-dot Rb, dashed K). The absorption image is not part of this panel. data.csv
• panel (f-2): Panel (f), right: projected 1D line density $P_X$ ($\mu$m$^{-1}$), horizontal, against $X_{CAM}$ ($\mu$m), vertical and increasing downward as printed, on ground at $\varphi = 30.9^\circ$. Rb data in red, K data in cyan, simulations with an instantaneous switch-off in black (dash-dot Rb, dashed K). data.csv
• panel (f-3): Panel (f), image: $^{87}$Rb column density on ground at $\varphi = 30.9^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White solid lines: contours of the simulated Rb density with an instantaneous switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (f-4): Panel (f), image: $^{41}$K column density on ground at $\varphi = 30.9^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White dashed lines: contours of the simulated K density with an instantaneous switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (g-1): Panel (g), top: projected 1D line density $P_Y$ ($\mu$m$^{-1}$) against $Y_{CAM}$ ($\mu$m) of the $^{41}$K and $^{87}$Rb mixture after free expansion on ground at $\varphi = 60.6^\circ$. Rb data in red, K data in cyan, Gross-Pitaevskii simulations with an instantaneous switch-off in black (dash-dot Rb, dashed K). The absorption image is not part of this panel. data.csv
• panel (g-2): Panel (g), right: projected 1D line density $P_X$ ($\mu$m$^{-1}$), horizontal, against $X_{CAM}$ ($\mu$m), vertical and increasing downward as printed, on ground at $\varphi = 60.6^\circ$. Rb data in red, K data in cyan, simulations with an instantaneous switch-off in black (dash-dot Rb, dashed K). data.csv
• panel (g-3): Panel (g), image: $^{87}$Rb column density on ground at $\varphi = 60.6^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White solid lines: contours of the simulated Rb density with an instantaneous switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (g-4): Panel (g), image: $^{41}$K column density on ground at $\varphi = 60.6^\circ$, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White dashed lines: contours of the simulated K density with an instantaneous switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (h-1): Panel (h), top: projected 1D line density $P_Y$ ($\mu$m$^{-1}$) against $Y_{CAM}$ ($\mu$m) of the $^{41}$K and $^{87}$Rb mixture after free expansion in microgravity. Rb data in red, K data in cyan, Gross-Pitaevskii simulations with an instantaneous switch-off in black (dash-dot Rb, dashed K). The absorption image is not part of this panel. data.csv
• panel (h-2): Panel (h), right: projected 1D line density $P_X$ ($\mu$m$^{-1}$), horizontal, against $X_{CAM}$ ($\mu$m), vertical and increasing downward as printed, in microgravity. Rb data in red, K data in cyan, simulations with an instantaneous switch-off in black (dash-dot Rb, dashed K). data.csv
• panel (h-3): Panel (h), image: $^{87}$Rb column density in microgravity, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White solid lines: contours of the simulated Rb density with an instantaneous switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv
• panel (h-4): Panel (h), image: $^{41}$K column density in microgravity, divided by its maximum (negative values set to 0), against $Y_{CAM}$ and $X_{CAM}$ ($\mu$m), $X_{CAM}$ increasing downward as printed. White dashed lines: contours of the simulated K density with an instantaneous switch-off at 0.1, 0.2, 0.5, 0.9 of its maximum. The print overlays Rb (red) and K (cyan) in one image. data.csv

Fig. 6

Illustrative figure, no extractable data. Shown in the paper PDF.

Fig. 7

• panel (a): MOT atom number (log scale) against loading time in ms: $^{87}$Rb (red line), $^{41}$K (blue) and $^{41}$K loaded together with $^{87}$Rb (blue ringed in red). Black dashed lines mark the saturation values. data.csv
• panel (b): Atom number (log scale) against hold time $t_{\mathrm{hold}}$ in ms in the magnetic trap: $^{87}$Rb (red), $^{41}$K (blue) and $^{41}$K with $^{87}$Rb trapped simultaneously (blue ringed in red), each with a dashed exponential fit. The printed lifetime labels are not drawn. data.csv

Cite

Baptist Piest et al. (27 authors). Apparatus for quantum-mixture research in microgravity. Nat. Commun. 17, 7573 (2026). https://doi.org/10.1038/s41467-026-75968-9

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