Direct Frequency-Comb-Driven Raman Transitions in the Terahertz Range

Solaro, Cyrille; Drewsen, Michael; DePalatis, M. V.; Fisher, Karin; Meyer, S.

doi:10.15278/isms.2018.mg05

Cited by 10 publications

(14 citation statements)

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“…We prepare a trapped 40 CaH + molecular ion at rest in a single, known quantum state and coherently drive stimulated Raman transitions between levels of different rotational quantum numbers J, ranging from J = 1 to J = 6 in the electronic and vibrational ground state manifold. These transitions, with frequencies between 1.4 THz and 3.2 THz, are driven using an optical frequency comb [17][18][19][20] with a spectrum centered in the range between 800 nm and 850 nm, far off-resonance from most vibrational and all electronic transitions [18]. Crucially, the frequency comb spans a large frequency range (∼ 10 THz) and serves as a versatile and agile tool.…”

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“…Moreover, coherent manipulation of molecular states may lead to new capabilities, such as alignment and orientation of molecules starting from pure initial states, preparation of squeezed or Schrödinger cat-type states of rotation, and precisely state-controlled dissociation of molecular ions. ACKNOWLEDGEMENT We thank Flavio C. Cruz and Andrei Kazakov for carefully reading and providing feed- Crucially, there are many comb teeth pairs with equal difference n σ − n π = N that will contribute to driving the transition, as long as the bandwidth of the comb is significantly larger than the corresponding f Raman and dispersive phase variations over the comb spectrum are sufficiently small [20].…”

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Frequency-comb spectroscopy on pure quantum states of a single molecular ion

Chou

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Kurz

et al. 2020

Science

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Spectroscopy is a powerful tool for studying molecules and is commonly performed on large thermal molecular ensembles that are perturbed by motional shifts and interactions with the environment and one another, resulting in convoluted spectra and limited resolution. Here, we use generally applicable quantum-logic techniques to prepare a trapped molecular ion in a single quantum state, drive terahertz rotational transitions with an optical frequency comb, and read out the final state non-destructively, leaving the molecule ready for further manipulation. We resolve rotational transitions to 11 significant digits and derive the rotational constant of 40 CaH + to be B R = 142 501 777.9(1.7) kHz. Our approach suits a wide range of molecular ions, including polyatomics and species relevant for tests of fundamental physics, chemistry, and astrophysics.Precision molecular spectroscopy produces information that is essential to understand molecular properties and functions, which underpin chemistry and biology. In particular, microwave rotational spectroscopy can precisely determine various aspects of molecular structure, such as bond lengths and angles, and help identify molecules. However, even in a dilute gas, where the interaction with surrounding molecules is reduced, spectroscopic experiments often fall short of the ultimate resolution set by the natural linewidth of the transitions. This is due to effects that crowd and blur molecular spectra, such as uncontrolled nuclear, rotational, vibrational, and electronic states, line shifts and broadening from external fields, reduced interaction time from time-of-flight, and the Doppler effect. These limitations have motivated efforts toward trapping molecules and cooling them close to absolute zero temperature. Laser cooling and trapping [1-3], which revolutionized atomic physics, have enabled formation of molecules from cold atoms [4] and precision molecular spectroscopy [5]. Direct laser cooling of molecules shows promise for species with advantageous level structures that only require a few laser wavelengths [6-8], but is infeasible for the vast majority of molecules.Furthermore, even with trapped and cooled molecules [9], commonly used detection methods, such as state-dependent photo-dissociation or ionization [10,11], destroy the molecules under study, making them unavailable for further manipulation.In this work, we perform high resolution spectroscopy on rotational states of a molecular ion using methods that are generally applicable to a broad range of molecular ions, which are readily trapped in electromagnetic potentials [12] and cooled by coupling to co-trapped atomic ions amenable to laser cooling [13,14]. The long interrogation times and low translational temperature enabled by trapping and sympathetic cooling lead to high resolution [15], which has, among other advances, enabled the most stringent test of fundamental theory carried out by molecular ions [16]. We prepare a trapped 40 CaH + molecular ion at rest in a single, known quantum state and coherently ...

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Frequency-comb spectroscopy on pure quantum states of a single molecular ion

Chou

Collopy

Kurz

et al. 2020

Science

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“…However, even fine-or hyperfine transitions can serve as narrow reference lines when combined with transitions in neutral or singly-charged atoms. Possible candidates for which narrow lines and at least four stable isotopes exist are Yb and in particular Ca, since experimental data for Ca + is already available Shi et al, 2017;Solaro et al, 2017). Once nonlinearities in the King plot have been observed, the challenge remains to isolate α NP from all other standard physics higher order effects neglected in Eq.…”

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confidence: 99%

Highly charged ions: Optical clocks and applications in fundamental physics

et al. 2018

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Recent developments in frequency metrology and optical clocks have been based on electronic transitions in atoms and singly charged ions as references. The control over all relevant degrees of freedom in these atoms has enabled relative frequency uncertainties at a level of a few parts in 10 −18 . This accomplishment not only allows for extremely accurate time and frequency measurements, but also to probe our understanding of fundamental physics, such as a possible variation of fundamental constants, a violation of the local Lorentz invariance, and the existence of forces beyond the Standard Model of Physics. In addition, novel clocks are driving the development of sophisticated technical applications. Crucial for applications of clocks in fundamental physics are a high sensitivity to effects beyond the Standard Model and Einstein's Theory of Relativity and a small frequency uncertainty of the clock. Highly charged ions offer both. They have been proposed as highly accurate clocks, since they possess optical transitions which can be extremely narrow and less sensitive to external perturbations compared to current atomic clock species. The large selection of highly charged ions in different charge states offers narrow transitions that are among the most sensitive ones for a change in the finestructure constant and the electron-to-proton mass ratio, as well as other new physics effects. Recent experimental advances in trapping and sympathetic cooling of highly charged ions will in the future enable advanced quantum logic techniques for controlling motional and internal degrees of freedom and thus enable high accuracy optical spectroscopy. Theoretical progress in calculating the properties of selected highly charged ions has allowed the evaluation of systematic shifts and the prediction of the sensitivity to the "new physics" effects. New theoretical challenges and opportunities emerge from relativistic, quantum electrodynamics, and nuclear size contributions that become comparable with interelectronic correlations. This article reviews the current status of theory and experiment in the field, addresses specific electronic configurations and systems which show the most promising properties for research, their potential limitations, and the techniques for their study.

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“…Related phenomenological advancements have mostly been corresponding to knowledge improvements of atomic internal structure and its sensitivity to external disturbances. The development of advanced methods for laser frequency stabilization complemented by progress in generation and control of optical frequency combs seen in the past few years have recently enabled the pioneering excitations of Raman transitions in the gigahertz [5,6] and terahertz domain [7] as well as new atomic spectroscopy methods [8].…”

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confidence: 99%

Optical frequency analysis on dark state of a single trapped ion

et al. 2020

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We demonstrate an optical frequency analysis method using the Fourier transform of detection times of fluorescence photons emitted from a single trapped 40 Ca + ion. The response of the detected photon rate to the relative laser frequency deviations is recorded within the slope of a dark resonance formed in the lambda-type energy level scheme corresponding to two optical dipole transitions. This approach enhances the sensitivity to the small frequency deviations and does so with reciprocal dependence on the fluorescence rate. The employed lasers are phase locked to an optical frequency comb, which allows for precise calibration of optical frequency analysis by deterministic modulation of the analyzed laser beam with respect to the reference beam. The attainable high signal-to-noise ratios of up to a MHz range of modulation deviations and up to a hundred kHz modulation frequencies promise the applicability of the presented results in a broad range of optical spectroscopic applications.

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Direct Frequency-Comb-Driven Raman Transitions in the Terahertz Range

Cited by 10 publications

References 36 publications

Frequency-comb spectroscopy on pure quantum states of a single molecular ion

Frequency-comb spectroscopy on pure quantum states of a single molecular ion

Highly charged ions: Optical clocks and applications in fundamental physics

Optical frequency analysis on dark state of a single trapped ion

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