© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

Chinese Physics B

Compensation of Differential AC-Stark Shift in Trapped Ion Qubits via Auxiliary Laser Field

Z D Zhang, Wenbo Su, Yi Xie, Ting Chen, Chun-Wang Wu, Wei Wu, J Zhang, Ping‐Xing Chen

Published Jun 22, 2026• 0 citations

Abstract

Abstract Encoding qubit states in the ground states of zero nuclear spin trapped ions has the advantages of both long coherence time and simple energy structure. High-fidelity quantum operations on trapped-ion qubits are often hindered by the differential AC-Stark shift induced by state manipulation lasers. Here we propose and demonstrate a novel compensation approach that addresses this challenge without introducing additional laser sources or sacrificing the power of the manipulation lasers. Our method leverages an existing optical transition to induce a counteracting light shift on one of the qubit states. We experimentally validate this scheme using a single trapped 40 Ca + ion. We show that the differential AC-Stark shift induced by 393 nm Raman lasers on a ground-state Zeeman qubit can be compensated by a detuned 729 nm shelving laser. Conversely, we also demonstrate compensation of the shift induced by a 729 nm laser on a ground-to-metastable qubit using one of the 393 nm Raman beams. In both cases, the residual differential shift is suppressed by approximately two orders of magnitude compared to the uncompensated case. This method is universally applicable to various trapped-ion systems, offering a practical and power-effcient route to mitigate a key source of gate infidelity.

DOI: 10.1088/1674-1056/ae7fff

Related papers

Measurement and compensation of optical Stark shifts for manipulating the terahertz-separated qubit in C40a+

Shinsuke Haze, Rekishu Yamazaki, Kenji Toyoda +1 more

We describe the measurement and compensation of optical Stark shifts induced by an off-resonant pulse for manipulating the terahertz-separated states $3\text{ }{^{2}D}_{3/2}--3\text{ }{^{2}D}_{5/2}$, in a single trapped ${^{40}\text{C}\text{a}}^{+}$ ion. These states can be used as a quantum bit and are coupled by a two-photon stimulated Raman transition with phase-locked light sources bridged by an optical comb generator. The induced optical Stark shift is measured by Ramsey interferometry. We estimate the power ratio of Raman beams that cancel the level shift with an uncertainty of 170 Hz. A shift of the same amount as this uncertainty is estimated to give rise to an infidelity of approximately $7.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ during a $\ensuremath{\pi}/2$ rotation operation.

Physical Review A•Nov 11, 2009•5 citations

Precision polarization tuning for light shift mitigation in trapped-ion qubits

Hengchao Tu, Chunyang Luan, Menglin Zou +3 more

Trapped-ion qubits are among the most promising candidates for quantum computing, quantum information processing, and quantum simulation. In general, trapped ions are considered to have sufficiently long coherence times, which are mainly characterized under laser-free conditions. However, in reality, essential laser fields for quantum manipulation introduce residual light shift, which seriously degrades the coherence due to power fluctuations. Here, we present a comprehensive study of ac Stark shifts in the hyperfine energy levels of the Yb + 171 ion, revealing an asymmetric light shift between two circular polarizations in the clock qubit and pronounced vector light shifts in the Zeeman qubits. By precisely tuning these polarizations, a remarkable enhancement in coherence time is observed, reaching over a 100-fold for the clock qubit and more than 10-fold for the Zeeman qubits, when comparing conditions of maximum and minimum shifts. These findings advance the practical realization of scalable trapped-ion quantum processors, enabling deep quantum circuit execution and long-duration adiabatic operations.

arXiv:2504.19474•Physical Review Research•Sep 3, 2025•4 citations

Precision Measurement and Compensation of Optical Stark Shifts for an Ion-Trap Quantum Processor

Hartmut Häffner, S. Gulde, Mark Riebe +5 more

Using optical Ramsey interferometry, we precisely measure the laser-induced ac-Stark shift on the S(1/2)-D(5/2) "quantum bit" transition near 729 nm in a single trapped 40Ca+ ion. We cancel this shift using an additional laser field. This technique is of particular importance for the implementation of quantum information processing with cold trapped ions. As a simple application we measure the atomic phase evolution during a n x 2 pi rotation of the quantum bit.

arXiv:physics/0212040•Physical Review Letters•Apr 9, 2003•146 citations

Engineering large Stark shifts for control of individual clock state qubits

A. C. Lee, J. Smith, Philip Richerme +4 more

In quantum information science, the external control of qubits must be balanced with the extreme isolation of the qubits from the environment. Atomic qubit systems typically mitigate this balance through the use of gated laser fields that can create superpositions and entanglement between qubits. Here we propose the use of high-order optical Stark shifts from optical fields to manipulate the splitting of atomic qubits that are insensitive to other types of fields. We demonstrate a fourth-order ac Stark shift in a trapped atomic ion system that does not require extra laser power beyond that needed for other control fields. We individually address a chain of tightly spaced trapped ions and show how these controlled shifts can produce an arbitrary product state of 10 ions as well as generate site-specific magnetic field terms in a simulated spin Hamiltonian.

arXiv:1604.08840•Physical Review A•Oct 7, 2016•49 citations

Suppression of differential light shifts in ground and metastable trapped-ion qubits

Drew Parks, Thomas Dellaert, Patrick McMillin +3 more

In the presence of a magnetic field, hyperfine clock qubits can acquire a vector differential light shift that can be tuned via polarization to suppress the total differential light shift of high-power, off-resonant laser light. We experimentally measure this "magic" polarization condition, suppressing differential light shifts in both the ${}^2\mathrm{S}_{1/2}$ ground and ${}^2\mathrm{F}_{7/2}^o$ metastable clock qubits of $^{171}\mathrm{Yb}^+$. We present calculations of the minimum bias magnetic fields required to suppress differential light shifts in the ground state clock qubits of commonly trapped ion species, finding that they are below the strengths of fields already typically present in experiments. We further present methods for metastable clock-qubit control in $^{171}\mathrm{Yb}^+$, demonstrating a state preparation and measurement infidelity of $2.9^{+3.0}_{-1.5}\times10^{-4}$ ($-35 \pm 4 \, \mathrm{dB}$).

arXiv:2606.02543•Jun 1, 2026•0 citations

Entangling ions with engineered light gradients

Tommaso Faorlin, Lorenz Panzl, Phoebe Grosser +12 more

Spectral crowding of collective motional modes limits the fidelity of entangling interactions in trapped-ion quantum processors by inducing off-resonant coupling to spectator modes. We introduce a geometric-phase entangling interaction driven by a transverse, time-dependent structured-light force. By applying the force in a plane orthogonal to the optical propagation direction, we reduce the effects of spectral crowding while preserving single-ion addressing. The scheme is compatible with arbitrary qubit encodings, provided that the qubit states experience a differential AC Stark shift. We experimentally realise high-fidelity two-qubit gates with error rates below $5\times10^{-3}$ in ion crystals containing up to 12 ions confined within a single potential well. These results establish gradient-field light-shift gates as a scalable approach to high-fidelity entangling generation in spectrally crowded trapped-ion systems.

quant-pharXiv:2603.07548•Physical Review Letters•Mar 10, 2026•0 citations

Abstract Encoding qubit states in the ground states of zero nuclear spin trapped ions has the advantages of both long coherence time and simple energy structure. High-fidelity quantum operations on trapped-ion qubits are often hindered by the differential AC-Stark shift induced by state manipulation lasers. Here we propose and demonstrate a novel compensation approach that addresses this challenge without introducing additional laser sources or sacrificing the power of the manipulation lasers. Our method leverages an existing optical transition to induce a counteracting light shift on one of the qubit states. We experimentally validate this scheme using a single trapped 40 Ca + ion. We show that the differential AC-Stark shift induced by 393 nm Raman lasers on a ground-state Zeeman qubit can be compensated by a detuned 729 nm shelving laser. Conversely, we also demonstrate compensation of the shift induced by a 729 nm laser on a ground-to-metastable qubit using one of the 393 nm Raman beams. In both cases, the residual differential shift is suppressed by approximately two orders of magnitude compared to the uncompensated case. This method is universally applicable to various trapped-ion systems, offering a practical and power-effcient route to mitigate a key source of gate infidelity.

We describe the measurement and compensation of optical Stark shifts induced by an off-resonant pulse for manipulating the terahertz-separated states

3\text{ }{^{2}D}_{3/2}--3\text{ }{^{2}D}_{5/2}

, in a single trapped

{^{40}\text{C}\text{a}}^{+}

ion. These states can be used as a quantum bit and are coupled by a two-photon stimulated Raman transition with phase-locked light sources bridged by an optical comb generator. The induced optical Stark shift is measured by Ramsey interferometry. We estimate the power ratio of Raman beams that cancel the level shift with an uncertainty of 170 Hz. A shift of the same amount as this uncertainty is estimated to give rise to an infidelity of approximately $7.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ during a $\ensuremath{\pi}/2$ rotation operation.

Trapped-ion qubits are among the most promising candidates for quantum computing, quantum information processing, and quantum simulation. In general, trapped ions are considered to have sufficiently long coherence times, which are mainly characterized under laser-free conditions. However, in reality, essential laser fields for quantum manipulation introduce residual light shift, which seriously degrades the coherence due to power fluctuations. Here, we present a comprehensive study of ac Stark shifts in the hyperfine energy levels of the Yb + 171 ion, revealing an asymmetric light shift between two circular polarizations in the clock qubit and pronounced vector light shifts in the Zeeman qubits. By precisely tuning these polarizations, a remarkable enhancement in coherence time is observed, reaching over a 100-fold for the clock qubit and more than 10-fold for the Zeeman qubits, when comparing conditions of maximum and minimum shifts. These findings advance the practical realization of scalable trapped-ion quantum processors, enabling deep quantum circuit execution and long-duration adiabatic operations.

In quantum information science, the external control of qubits must be balanced with the extreme isolation of the qubits from the environment. Atomic qubit systems typically mitigate this balance through the use of gated laser fields that can create superpositions and entanglement between qubits. Here we propose the use of high-order optical Stark shifts from optical fields to manipulate the splitting of atomic qubits that are insensitive to other types of fields. We demonstrate a fourth-order ac Stark shift in a trapped atomic ion system that does not require extra laser power beyond that needed for other control fields. We individually address a chain of tightly spaced trapped ions and show how these controlled shifts can produce an arbitrary product state of 10 ions as well as generate site-specific magnetic field terms in a simulated spin Hamiltonian.

In the presence of a magnetic field, hyperfine clock qubits can acquire a vector differential light shift that can be tuned via polarization to suppress the total differential light shift of high-power, off-resonant laser light. We experimentally measure this "magic" polarization condition, suppressing differential light shifts in both the

{}^2\mathrm{S}_{1/2}

ground and

{}^2\mathrm{F}_{7/2}^o

metastable clock qubits of

^{171}\mathrm{Yb}^+

. We present calculations of the minimum bias magnetic fields required to suppress differential light shifts in the ground state clock qubits of commonly trapped ion species, finding that they are below the strengths of fields already typically present in experiments. We further present methods for metastable clock-qubit control in

^{171}\mathrm{Yb}^+

, demonstrating a state preparation and measurement infidelity of

2.9^{+3.0}_{-1.5}\times10^{-4}

(

-35 \pm 4 \, \mathrm{dB}

).

Spectral crowding of collective motional modes limits the fidelity of entangling interactions in trapped-ion quantum processors by inducing off-resonant coupling to spectator modes. We introduce a geometric-phase entangling interaction driven by a transverse, time-dependent structured-light force. By applying the force in a plane orthogonal to the optical propagation direction, we reduce the effects of spectral crowding while preserving single-ion addressing. The scheme is compatible with arbitrary qubit encodings, provided that the qubit states experience a differential AC Stark shift. We experimentally realise high-fidelity two-qubit gates with error rates below

5\times10^{-3}

in ion crystals containing up to 12 ions confined within a single potential well. These results establish gradient-field light-shift gates as a scalable approach to high-fidelity entangling generation in spectrally crowded trapped-ion systems.