Doppler cooling thermometry of a multilevel ion in the presence of micromotion

Sikorsky, Tomas; Meir, Ziv; Akerman, Nitzan; Ben-shlomi, Ruti; Ozeri, Roee

doi:10.1103/physreva.96.012519

Cited by 22 publications

(35 citation statements)

References 35 publications

(62 reference statements)

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“…In order to approximate the photon scattering during laser cooling, we employ well-established semiclassical simplifying assumptions [2,9,[13][14][15][16][17][18][19][20][21][22][23]. In Sec.…”

Section: Introductionmentioning

confidence: 99%

Far-from-equilibrium noise-heating and laser-cooling dynamics in radio-frequency Paul traps

et al. 2019

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We study the stochastic dynamics of a particle in a periodically driven potential. For atomic ions trapped in radio-frequency Paul traps, noise heating and laser cooling typically act slowly in comparison with the unperturbed motion. These stochastic processes can be accounted for in terms of a probability distribution defined over the action variables, which would otherwise be conserved within the regular regions of the Hamiltonian phase space. We present a semiclassical theory of low-saturation laser cooling applicable from the limit of low-amplitude motion to large-amplitude motion, accounting fully for the time-dependent and anharmonic trap. We employ our approach to a detailed study of the stochastic dynamics of a single ion, drawing general conclusions regarding the nonequilibrium dynamics of laser-cooled trapped ions. We predict a regime of anharmonic motion in which laser cooling becomes diffusive (i.e., it is equally likely to cool the ion as it is to heat it), and can also turn into effective heating. This implies that a high-energy ion could be easily lost from the trap despite being laser cooled; however, we find that this loss can be counteracted using a laser detuning much larger than Doppler detuning.

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Section: Introductionmentioning

confidence: 99%

Far-from-equilibrium noise-heating and laser-cooling dynamics in radio-frequency Paul traps

et al. 2019

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“…We repeated this sequence 100-500 times in determining the temperature. Since this thermometry method has a good sensitivity in a temperature range of hundreds of mK to 10 K [24], we intentionally heated the ion in step (ii).…”

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confidence: 99%

Cooling Dynamics of a Single Trapped Ion via Elastic Collisions with Small-Mass Atoms

et al. 2018

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We demonstrated sympathetic cooling of a single ion in a buffer gas of ultracold atoms with small mass. Efficient collisional cooling was realized by suppressing collision-induced heating. We attempt to explain the experimental results with a simple rate equation model and provide a quantitative discussion of the cooling efficiency per collision. The knowledge we obtained in this work is an important ingredient for advancing the technique of sympathetic cooling of ions with neutral atoms.PACS numbers: 37.10. Ty,03.67.Lx Sympathetic cooling, where we thermally contact two distinct systems at different temperatures, is an effective method for cooling an object to a desired energy regime. Nowadays, this is commonly used in the field of low-temperature physics for producing a cold sample for a molecular beam or degenerate atomic gases. The elemental mechanism of this technique extracts energy from a target object through interaction (normally by collisions) with a coolant system. In cooling of translational motion, for example, an exchange of moment between the two systems can remove kinetic energy from the thermal system, and eventually they reach thermal equilibrium, resulting in cooling of the target object.To introduce an ultracold atomic gas as a coolant for trapped ions is attractive, since collisions with ultracold atoms enable efficient cooling of a number of vibrational modes simultaneously. It is beneficial for many applications, for example, continuous cooling of ion qubits in quantum information processing. In addition, this method has been proven to be effective for the cooling of atomic or molecular systems, especially when no conventional laser cooling transition is accessible, as demonstrated in rotational-vibrational cooling of molecular ions [1,2].In buffer-gas cooling of a charged particle, however, the situation is not as simple as in the usual schemes, e.g., evaporation or sympathetic cooling in a mixture of neutral gases. This is simply attributed to the dynamics of trapping it in a radiofrequency (RF) trap, where slow (secular) and rapid (micro) motion are superimposed on the motion of the ion. The main point is that an abrupt interception of coherent ion motion by an atom-ion collision complicates the kinetics of the ion. Importantly, an ion can be either cooled or even heated, depending on the instantaneous phase of micromotion at the moment of a collision, which prevents efficient collisional cooling [3]. In addition, this peculiar feature modifies the energy distribution of an ion by inducing a deviation from a normal (Maxwell-Boltzmann) distribution to * haze@ils.uec.ac.jp a super-statistical (so-called Tsallis) distribution accompanied with a power-law tail in a high-energy region [4][5][6]. These subjects have been pointed out since the early stages of ion trapping experiments [7], and they were recently revisited again in conjunction with the rapidly growing field of ultracold atom-ion hybrid systems [8].A key parameter for characterizing the kinetics of the ion in a buffer gas is t...

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“…An important tool employed to control the dynamics of an ion and break the conserved quantities is laser cooling, a well established method for removing entropy, e.g. from a trapped ion's motion [2][3][4][5][6][7][8][9][10][11][12][13][14]. A stochastic process by * haggaila@gmail.com its very nature, laser cooling is based on the absorption of photons with a narrow momentum bandwidth determined by the laser, followed by a spontaneous emission of photons with randomly directed momenta.…”

Section: Introduction and Main Resultsmentioning

confidence: 99%

“…Interesting extensions of the theory could include more general electronic level structures [14,45], and applying the action-angle framework to setups where power-law distributions in energy (in an averaged sense) were predicted for collisions of ions with neutral atoms [46][47][48][49]. The interplay of micromotion, noise and laser cooling is of significant importance for applications in quantum information processing and the operation of quantum gates and entanglement operations with trapped ions [19,22,26,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64].…”

Section: Discussionmentioning

confidence: 99%

Tuning nonthermal distributions to thermal ones in time-dependent Paul traps

Landa

2019

Phys. Rev. A

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We study the probability distribution of an atomic ion being laser-cooled in a periodically-driven Paul trap using a Floquet approach to the semiclassical photon scattering dynamics. We show that despite the microscopic nonequilibrium forces, a stationary thermal-like exponential distribution can be obtained in the Hamiltonian action, or equivalently in the number of quanta (phonons) of the motion linearized about the zero of the potential. At the presence of additional stray electric fields, the ion is pushed from the origin of the potential and set into a large-amplitude driven oscillation, and above a threshold amplitude of such "excess micromotion", the action distribution of excitations about the driven oscillation broadens and becomes distinctly nonthermal. We find that by a proper choice of the laser detuning the distribution can be made exponential again, with a mean phonon number close to that of the Doppler cooling limit. We derive a relation allowing to deduce just from the experimentally observable photon scattering rate both the required detuning for optimal cooling and the final mean phonon number. These results are important for quantum information processing and other applications, and in particular the derived approach can be applied to crystals of trapped ions in planar configurations, where the driven motion of ions is unavoidable.

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Doppler cooling thermometry of a multilevel ion in the presence of micromotion

Cited by 22 publications

References 35 publications

Far-from-equilibrium noise-heating and laser-cooling dynamics in radio-frequency Paul traps

Far-from-equilibrium noise-heating and laser-cooling dynamics in radio-frequency Paul traps

Cooling Dynamics of a Single Trapped Ion via Elastic Collisions with Small-Mass Atoms

Tuning nonthermal distributions to thermal ones in time-dependent Paul traps

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