Absolute single-ion thermometry

Abstract

We describe and experimentally implement a single-ion local thermometry technique with absolute sensitivity adaptable to all laser-cooled atomic ion species. The technique is based on the velocity-dependent spectral shape of a quasi-dark resonance tailored in a J → J transition such that the two driving fields can be derived from the same laser source leading to a negligible relative phase shift. We validated the method and tested its performances in an experiment on a single 88 Sr + ion cooled in a surface radio-frequency trap. We first applied the technique to characterise the heating-rate of the surface trap. We then measured the stationary temperature of the ion as a function of cooling laser detuning in the Doppler regime. The results agree with theoretical calculations, with an absolute error smaller than 100 µK at 500 µK, in a temperature range between 0.5 and 3 mK and in the absence of adjustable parameters. This simple-to-implement and reliable method opens the way to fast absolute measurements of single-ion temperatures in future experiments dealing with heat transport in ion chains or thermodynamics at the single-ion level.PACS numbers: 37.10.Rs, 32.70.Jz, 37.10.Vz Laser cooled trapped ions offer the opportunity for a precise quantum control at the single particle level [1] that triggered the development of ion-based platforms dedicated to quantum information processing [2,3]. Cold ion based systems have also been proposed and applied for testing thermodynamics in the quantum regime [4,5] and quantum heat transport in network chains [6][7][8][9]. The latter applications need the development of thermometry techniques that should characterise in a short time the velocity distribution of a single-ion that possibly interacts with other ions in its direct environment. Since the first demonstrations of laser cooling of trapped ions [10,11], experimental thermometry tools have been developed together with theoretical models predicting stationary temperatures, for instance in the case of Doppler cooling [12,13]. Among the thermometry techniques for trapped ions we can distinguish between three large families.

Three-laser coherent population trapping in a multi-lambda system: theory, experiment and applications

“…Varying the propagation direction of the repumper in the plane orthogonal to B would then tune the sensitivity of these dark resonances to the ion's temperature, i.e., the range of measurable temperatures with the method. Such a method would have the possibility of tuning sensitivity with angle as in [24] and the independence of the laser linewidths when both probe and repumper are derived from the same source and tuned via two independent AOMs as in [25].…”

“…The narrow feature of the resonances is especially useful to study the motional states of few ions because the resonances widths are specially sensitive to ions' motion [21][22][23]. This makes it possible to use it to measure the temperature of single trapped ions [24,25] as well as using EIT to perform cooling below the Doppler limit of single ions [26,27] and even multimode cooling of long ion chains and crystals [28][29][30]. This technique proved to be a robust cooling method towards coherent control of multiple ions simul- * schmiegelow@df.uba.ar taneously with applications in quantum computing and quantum simulation [31,32].…”

Large‐Scale Fabrication of Surface Ion Traps on a 300 mm Glass Wafer

“…In the past decades, trapped ion technologies have been rapidly developed for applications in quantum computing, [ 1–3 ] simulation, [ 4,5 ] and sensing. [ 6,7 ] Invented in 2005 [ 8 ] and demonstrated for the first time in 2006, [ 9 ] the surface ion trap geometry, in which all the electrodes lie in the same plane, enables microfabrication flexibility for complex electrode designs, [ 10,11 ] optoelectronic integration [ 12,13 ] enhancing then trap scalability and functionality. Trapped ions are among the most promising systems to realize scalable quantum computers due to their capability in precise manipulation of multiple ion qubits with high fidelity [ 14 ] and long coherence time.…”

Spectroscopy of Trapped ¹³⁸Ba⁺ Ions for Atomic Parity Violation and Optical Clocks

“…We discuss this further with the spectra presented in Chapters 4 and 5. Calibrating the temperature in absolute terms from spectra is difficult since it requires precise knowledge of many experimental parameters; a method working around this achieving sub-mK accuracy has been demonstrated recently [148].…”