Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2210.11613

Quantum logic control and precision measurements of molecular ions in a ring trap -- a new approach for testing fundamental symmetries

Yan Zhou, Joshua O. Island, Grau, Matt

Published Oct 20, 2022• 2 citations
arXivHTMLPDF

Abstract

We present a new platform facilitating quantum logic control of polar molecular ions in a segmented ring ion trap, paving the way for precision measurements. This approach focuses on achieving near-unity state preparation and detection, as well as long spin coherence. A distinctive aspect lies in separating state preparation and detection conducted in a static frame, from parity-selective spin-precession in a rotating frame. This method can be applied to a wide range of ion species and will be used to search for the electron's electric dipole moment and the nuclear magnetic quadrupole moment.

DOI
10.48550/arxiv.2210.11613

Related papers

Quantum logic control and precision measurements of molecular ions in a ring trap: An approach for testing fundamental symmetries

Yan Zhou, Joshua O. Island, Matt Grau

This paper presents an experimental platform designed to facilitate quantum logic control of polar molecular ions in a segmented ring ion trap, paving the way for precision measurements. This approach focuses on achieving near-unity state preparation and detection, as well as long spin-precession coherence. A distinctive aspect lies in separating state preparation and detection conducted in a static frame from parity-selective spin precession in a rotating frame. Moreover, the method is designed to support spatially and temporally coincident measurements on multiple ions prepared in states with different sensitivity to the new physics of interest. This provides powerful techniques to probe and minimize potential sources of systematic error. While the primary focus of this paper is on detecting the electron's electric dipole moment (eEDM) using $^{232}\mathrm{ThF}^{+}$ ions, the proposed methodology holds promise for broader applications, particularly with ion species that exhibit enhanced sensitivity to the nuclear magnetic quadruple moment (nMQM).

Physical Review A•Mar 14, 2024•5 citations

Static Laboratory-Frame Polarization of a Trapped Molecular Ion for CP-Violation Searches

Fabian Wolf

Today's most sensitive experiments for detecting CP-violating permanent electric dipole moments (EDM) rely on molecular spectroscopy. The high sensitivity arises from large internal electric fields that interact with the constituents of the molecule. For molecular ions it has long been assumed that experiments with static polarization from dc electric fields are infeasible, as the ion's charge would either shift it to a field free region or eject it from the trap. This constraint appears to make single ion quantum-logic clocks, among the most precise measurement devices available, incompatible with EDM measurements. Here, we demonstrate that, under typical trapping conditions, heavy molecular ions with small $Ω/Λ$-doubling can be polarized by a static electric field while remaining confined in the Paul trap. This effect arises from a cancellation between the electrostatic force and the trap's ponderomotive force, resulting in an equilibrium position where the ion experiences a dc electric field component. Dynamic decoupling allows to implement co-magnetometry schemes in a single molecule and provides long interrogation times. This will allow the operation of a quantum-logic molecular radio-frequency clock in static electric fields, providing sensitivity to EDMs. Working with only a few ions and non-destructive detection techniques opens the door to the use of highly sensitive, rare, and radioactive molecular species as well as quantum-enhanced metrology schemes to achieve unprecedented levels of accuracy and precision.

physics.atom-phCross-listedarXiv:2511.14701•Nov 19, 2025

Quantum Logic Techniques for Transition Metal and Molecular Ions

Till Rehmert

High-precision spectroscopy of atomic and molecular ions is an established platform for investigating fundamental aspects of physics. An important step in this direction was the development of quantum logic techniques that enable the spectroscopy of ions whose electronic structure does not allow direct laser cooling. Particularly challenging in this context is the investigation of atomic and molecular systems with many long-lived metastable states. The preparation of a pure quantum state for spectroscopy purposes often requires the prior detection of these long-lived states. For molecular ions, schemes for the detection of their rotational degree of freedom have already been developed in the past. However, quantum logic control of transition metals, in which the many metastable states result from several valence electrons, remained elusive. In this cumulative thesis, the first experimental implementation of a quantum logic assisted scheme for internal state detection of atomic systems as complex as a titanium ion is presented. Furthermore, a scheme based on simultaneous co-magnetometry for measuring the Landé g factor was developed and demonstrated for different fine structure states in 48Ti+. The presented method allows the suppression of systematic uncertainties arising from varying magnetic fields at the position of the ion and can be transferred to a variety of other species. Crucial for quantum logic based applications is the reliable preparation of a two-ion crystal consisting of one spectroscopy ion and one logic ion. A third aspect of this work is the deterministic preparation of such a two-ion crystal. The method based on fluorescence imaging is associated with a significantly reduced calibration effort compared to other schemes and can be easily transferred to other combinations of spectroscopy and logic ions. The quantum logic control capabilities demonstrated in this work are applicable to a wide range of other atoms with complex electronic structures as well as to molecular ions. The investigation of transition metals can provide important reference data for the calibration of absorption spectra from astrophysical objects. Molecular ions have applications in the search for a possible variation of fundamental constants or the measurement of energy shifts caused by an electron electric dipole moment, both representing promising approaches to test the standard model of particle physics.

•Jan 1, 2026•0 citations

Quantum logic control and spectroscopy of a single molecular ion

Alejandra Collopy, David R. Leibrandt, Dietrich G. Leibfried +1 more

Quantum logic enables state preparation, readout and spectroscopy of otherwise difficult-to-study ions. Using the coupled harmonic motion shared between co-trapped ions, information can be transferred from the "spectroscopy" ion to the easily manipulated "logic" ion. With this technique we perform high-resolution terahertz-scale rotational spectroscopy of a single CaH+ molecular ion in pure states by leveraging a Ca+ ion as our logic ion. Entangled states between a CaH+ and a Ca+ have also been demonstrated, making molecular ions possible components of hybrid systems for quantum information processing. Because all our laser operations on the molecule are driving stimulated Raman transitions with high detuning, the technique promises to be generalizable to a wide variety of molecular ion species. Additionally, we study the systematic effects of the trap RF electric field on molecular levels and use it to obtain a measurement of the dipole moment of the charged molecule.

Optical and Quantum Sensing and Precision Metrology•Mar 4, 2021•0 citations

Quantum state preparation and control of single molecular ions

D Leibfried

Preparing molecules at rest and in a very pure quantum state is a long-standing aspiration in chemistry and physics, so far achieved only for a select set of molecules in dedicated experimental setups. Here, a quantum-limited combination of mass spectrometry and Raman spectroscopy is proposed that should be applicable to a wide range of molecular ions. Excitation of electrons in the molecule followed by uncontrolled decay and branching into several lower-energy states is avoided. Instead, the molecule is always confined to rotational states within the electronic and vibrational ground-state manifold, while a co-trapped atomic ion provides efficient entropy removal and allows for extraction of information about the molecule. The outlined techniques might enable the preparation, manipulation and measurement of a multitude of molecular ion species with the same instrument, with applications including, but not limited to, precise determination of molecular properties and fundamental tests of physics.

arXiv:1109.0208•New Journal of Physics•Feb 14, 2012•42 citations

Dipole-Phonon Quantum Logic with Trapped Polar Molecular Ions

Wesley C. Campbell, Eric R. Hudson

The interaction between the electric dipole moment of a trapped molecular ion and the phonon modes of the confined Coulomb crystal couples the orientation of the molecule to its motion. We consider the practical feasibility of harnessing this interaction to initialize, process, and read out quantum information encoded in molecular ion qubits without ever optically illuminating the molecules. We present two schemes wherein a molecular ion can be entangled with a cotrapped atomic ion qubit, providing, among other things, a means for molecular state preparation and measurement. We also show that virtual phonon exchange can significantly boost the range of the intermolecular dipole-dipole interaction, allowing strong coupling between widely separated molecular ion qubits.

arXiv:1909.02668•Physical Review Letters•Sep 14, 2020•31 citations
We present a new platform facilitating quantum logic control of polar molecular ions in a segmented ring ion trap, paving the way for precision measurements. This approach focuses on achieving near-unity state preparation and detection, as well as long spin coherence. A distinctive aspect lies in separating state preparation and detection conducted in a static frame, from parity-selective spin-precession in a rotating frame. This method can be applied to a wide range of ion species and will be used to search for the electron's electric dipole moment and the nuclear magnetic quadrupole moment.
This paper presents an experimental platform designed to facilitate quantum logic control of polar molecular ions in a segmented ring ion trap, paving the way for precision measurements. This approach focuses on achieving near-unity state preparation and detection, as well as long spin-precession coherence. A distinctive aspect lies in separating state preparation and detection conducted in a static frame from parity-selective spin precession in a rotating frame. Moreover, the method is designed to support spatially and temporally coincident measurements on multiple ions prepared in states with different sensitivity to the new physics of interest. This provides powerful techniques to probe and minimize potential sources of systematic error. While the primary focus of this paper is on detecting the electron's electric dipole moment (eEDM) using 232ThF+^{232}\mathrm{ThF}^{+}232ThF+ ions, the proposed methodology holds promise for broader applications, particularly with ion species that exhibit enhanced sensitivity to the nuclear magnetic quadruple moment (nMQM).
Today's most sensitive experiments for detecting CP-violating permanent electric dipole moments (EDM) rely on molecular spectroscopy. The high sensitivity arises from large internal electric fields that interact with the constituents of the molecule. For molecular ions it has long been assumed that experiments with static polarization from dc electric fields are infeasible, as the ion's charge would either shift it to a field free region or eject it from the trap. This constraint appears to make single ion quantum-logic clocks, among the most precise measurement devices available, incompatible with EDM measurements. Here, we demonstrate that, under typical trapping conditions, heavy molecular ions with small Ω/ΛΩ/ΛΩ/Λ-doubling can be polarized by a static electric field while remaining confined in the Paul trap. This effect arises from a cancellation between the electrostatic force and the trap's ponderomotive force, resulting in an equilibrium position where the ion experiences a dc electric field component. Dynamic decoupling allows to implement co-magnetometry schemes in a single molecule and provides long interrogation times. This will allow the operation of a quantum-logic molecular radio-frequency clock in static electric fields, providing sensitivity to EDMs. Working with only a few ions and non-destructive detection techniques opens the door to the use of highly sensitive, rare, and radioactive molecular species as well as quantum-enhanced metrology schemes to achieve unprecedented levels of accuracy and precision.
High-precision spectroscopy of atomic and molecular ions is an established platform for investigating fundamental aspects of physics. An important step in this direction was the development of quantum logic techniques that enable the spectroscopy of ions whose electronic structure does not allow direct laser cooling. Particularly challenging in this context is the investigation of atomic and molecular systems with many long-lived metastable states. The preparation of a pure quantum state for spectroscopy purposes often requires the prior detection of these long-lived states. For molecular ions, schemes for the detection of their rotational degree of freedom have already been developed in the past. However, quantum logic control of transition metals, in which the many metastable states result from several valence electrons, remained elusive. In this cumulative thesis, the first experimental implementation of a quantum logic assisted scheme for internal state detection of atomic systems as complex as a titanium ion is presented. Furthermore, a scheme based on simultaneous co-magnetometry for measuring the Landé g factor was developed and demonstrated for different fine structure states in 48Ti+. The presented method allows the suppression of systematic uncertainties arising from varying magnetic fields at the position of the ion and can be transferred to a variety of other species. Crucial for quantum logic based applications is the reliable preparation of a two-ion crystal consisting of one spectroscopy ion and one logic ion. A third aspect of this work is the deterministic preparation of such a two-ion crystal. The method based on fluorescence imaging is associated with a significantly reduced calibration effort compared to other schemes and can be easily transferred to other combinations of spectroscopy and logic ions. The quantum logic control capabilities demonstrated in this work are applicable to a wide range of other atoms with complex electronic structures as well as to molecular ions. The investigation of transition metals can provide important reference data for the calibration of absorption spectra from astrophysical objects. Molecular ions have applications in the search for a possible variation of fundamental constants or the measurement of energy shifts caused by an electron electric dipole moment, both representing promising approaches to test the standard model of particle physics.
Quantum logic enables state preparation, readout and spectroscopy of otherwise difficult-to-study ions. Using the coupled harmonic motion shared between co-trapped ions, information can be transferred from the "spectroscopy" ion to the easily manipulated "logic" ion. With this technique we perform high-resolution terahertz-scale rotational spectroscopy of a single CaH+ molecular ion in pure states by leveraging a Ca+ ion as our logic ion. Entangled states between a CaH+ and a Ca+ have also been demonstrated, making molecular ions possible components of hybrid systems for quantum information processing. Because all our laser operations on the molecule are driving stimulated Raman transitions with high detuning, the technique promises to be generalizable to a wide variety of molecular ion species. Additionally, we study the systematic effects of the trap RF electric field on molecular levels and use it to obtain a measurement of the dipole moment of the charged molecule.
Preparing molecules at rest and in a very pure quantum state is a long-standing aspiration in chemistry and physics, so far achieved only for a select set of molecules in dedicated experimental setups. Here, a quantum-limited combination of mass spectrometry and Raman spectroscopy is proposed that should be applicable to a wide range of molecular ions. Excitation of electrons in the molecule followed by uncontrolled decay and branching into several lower-energy states is avoided. Instead, the molecule is always confined to rotational states within the electronic and vibrational ground-state manifold, while a co-trapped atomic ion provides efficient entropy removal and allows for extraction of information about the molecule. The outlined techniques might enable the preparation, manipulation and measurement of a multitude of molecular ion species with the same instrument, with applications including, but not limited to, precise determination of molecular properties and fundamental tests of physics.
The interaction between the electric dipole moment of a trapped molecular ion and the phonon modes of the confined Coulomb crystal couples the orientation of the molecule to its motion. We consider the practical feasibility of harnessing this interaction to initialize, process, and read out quantum information encoded in molecular ion qubits without ever optically illuminating the molecules. We present two schemes wherein a molecular ion can be entangled with a cotrapped atomic ion qubit, providing, among other things, a means for molecular state preparation and measurement. We also show that virtual phonon exchange can significantly boost the range of the intermolecular dipole-dipole interaction, allowing strong coupling between widely separated molecular ion qubits.