Sandia holds cesium atoms on a 420-nanometer fiber with five milliwatts of light

The trap works by evanescent-field trapping: light extends just beyond the surface of the glass fiber, and cesium atoms are held in that field. The fiber is 420 nanometers across and the cesium rides in a halo around it ^[1]. Rock the fiber and the atoms shift side to side without falling off ^[13]. Jongmin Lee, a quantum sensing scientist at Sandia National Laboratories, makes that halo with lasers, and lasers also make heat, in a structure about 200 times thinner than a human hair, where heat can crack the atom guide ^[10][11].

The comparison can be run backwards. If 5 milliwatts is a quarter to a sixth of what earlier approaches needed, earlier approaches needed roughly 20 to 30 milliwatts ^[4][1]. The LED comparison Sandia offers implies a bulb drawing about 10 watts ^[2][2]. And the 150 nanowatts the team used for a second kind of measurement is about one thirty-three-thousandth of the trapping power ^[3][3].

The power figure describes light delivered to the trap. It leaves the sensor's actual performance unmeasured, and the phys.org account of the work carries no sensitivity, bias stability or drift number ^[17]. Those are the figures that decide whether a guided interferometer earns a place on an airframe. The wording of the low-power result matters too: what is reported at 150 nanowatts is measurements that mimic atom interferometry, not a full interferometer sequence run at that power ^[3].

Cutting laser power matters most for what it does to heat. Until recently the choice was between fragile designs that suspend a waveguide so atoms load efficiently but shatter under high heat, and sturdier designs ^[12]. Sandia's answer in this paper is a heat-resistant membrane-waveguide, described as a next-generation prototype ^[5]. "This idea has not been fully realized by the community for decades, due to challenges in dissipating heat from photonic devices in vacuum and in efficiently loading atoms around them," Lee said ^[7].

The nanofiber that carried these results served only as a testbed. Sandia calls nanofibers a convenient, reliable testbed that is currently impractical for real-world use, and the guided concept on a photonic integrated circuit is newer and less developed than the free-space alternative it would compete with ^[6][16]. "Our ultimate goal is to demonstrate this on a chip with a photonic integrated circuit, but our nanofiber results show a clear potential path toward chip-scale quantum inertial sensing," Lee said ^[9].