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:2003.01102 · Physical Review A

High-fidelity light-shift gate for clock-state qubits

Charles H. Baldwin, Bryce Bjork, Michael Foss‐Feig, John Gaebler, David Hayes, Mark Kokish, C. Langer, Jonathon A. Sedlacek, Daniel T. Stack, Grahame Vittorini

Published Jan 7, 2021• 34 citations
arXivHTMLPDF

Abstract

To date, the highest-fidelity quantum logic gates between two qubits have been achieved using the geometric-phase gate in trapped ions, with the two leading variants being the M\o{}lmer-S\o{}rensen gate and the light-shift (LS) gate. Both of these approaches have their respective advantages and challenges. For example, the latter is technically simpler and is natively insensitive to optical phases, but it has not been made to work directly on a clock-state qubit. We present a technique for implementing the LS gate that combines the best features of these two approaches: By using a small ($\ensuremath{\sim}\mathrm{MHz}$) detuning from a narrow (dipole-forbidden) optical transition, we are able to operate an LS gate directly on hyperfine clock states, achieving gate fidelities of $99.74(4)%$ using modest laser power at visible wavelengths. Current gate infidelities appear to be dominated by technical noise, and theoretical modeling suggests a path toward gate fidelity above $99.99%$.

DOI
10.1103/physreva.103.012603

Related papers

High-Fidelity Bell-State Preparation with Ca + 40 Optical Qubits

Craig R. Clark, Holly N. Tinkey, Brian C. Sawyer +10 more

Entanglement generation in trapped-ion systems has relied thus far on two distinct but related geometric phase gate techniques: Mølmer-Sørensen and light-shift gates. We recently proposed a variant of the light-shift scheme where the qubit levels are separated by an optical frequency [B. C. Sawyer and K. R. Brown, Phys. Rev. A 103, 022427 (2021)PLRAAN2469-992610.1103/PhysRevA.103.022427]. Here we report an experimental demonstration of this entangling gate using a pair of ^{40}Ca^{+} ions in a cryogenic surface-electrode ion trap and a commercial, high-power, 532 nm Nd:YAG laser. Generating a Bell state in 35 μs, we directly measure an infidelity of 6(3)×10^{-4} without subtraction of experimental errors. The 532 nm gate laser wavelength suppresses intrinsic photon scattering error to ∼1×10^{-5}.

arXiv:2105.05828•Physical Review Letters•Sep 24, 2021•165 citations

Efficient optical configurations for trapped-ion entangling gates

Aditya Milind Kolhatkar, Karan K. Mehta

High-fidelity and parallel realization in scalable platforms of the two-qubit entangling gates fundamental to universal quantum computing constitutes one of the largest challenges in implementing fault-tolerant quantum computation. Integrated optical addressing of trapped-ion qubits offers routes to scaling the high-fidelity optical control demonstrated to date in small systems. Here we show that in addition to scaling, capabilities practically enabled by integrated optics can substantially alleviate laser powers required for both light-shift (LS) and Molmer-Sorensen (MS) geometric phase gates acting on long-lived ground-state qubit encodings in a broad range of ion species. In the proposed gate schemes utilizing carrier nulling via ion positioning at phase-stable standing-wave (SW) nodes, our calculations suggest that suppressed spontaneous photon scattering at the SW node allows for gate drives operating at smaller Raman detunings, resulting in approximately an order-of-magnitude reduction in power requirement (and significantly larger in certain parameter regimes) for gates of a given duration and scattering-limited fidelity as compared to conventional running wave (RW)-based approaches. The SW schemes have the additional benefit of simultaneously eliminating undesired coherent couplings that typically limit gate speeds. Our work quantifies power requirements for multiple ion species and enhancements to be expected from carrier-nulled configurations practically enabled by integrated delivery, and informs experiments and systems for realization of fast and power-efficient laser-based entangling gates in scalable platforms.

arXiv:2509.05271•Physical Review A•Feb 12, 2026•2 citations

High-Fidelity Quantum Logic Gates Using Trapped-Ion Hyperfine Qubits

Christopher J. Ballance, T. P. Harty, Norbert M. Linke +2 more

We demonstrate laser-driven two-qubit and single-qubit logic gates with respective fidelities 99.9(1)% and 99.9934(3)%, significantly above the ≈99% minimum threshold level required for fault-tolerant quantum computation, using qubits stored in hyperfine ground states of calcium-43 ions held in a room-temperature trap. We study the speed-fidelity trade-off for the two-qubit gate, for gate times between 3.8 μs and 520 μs, and develop a theoretical error model which is consistent with the data and which allows us to identify the principal technical sources of infidelity.

arXiv:1406.5473•Physical Review Letters•Aug 4, 2016•774 citations

Trapped Ion Qubit Gates and Entanglement Driven by an Integrated Photonic Laser

Chris Caron, Zhenyu Wei, Andrei Isichenko +8 more

Trapped ions are a leading technology for quantum computing, but their reliance on bespoke tabletop laser and optical systems remains a major obstacle to scaling and robustness. Integrated silicon nitride lasers, compatible with future monolithic integration with surface electrode ion traps, have recently demonstrated frequency-selective qubit state preparation and measurement as well as interrogation of an optical clock transition. However, coherent qubit gates impose even more stringent requirements on laser phase noise, and their implementation with integrated laser sources has remained an outstanding challenge. Here, we use a visible-wavelength integrated Brillouin laser stabilized to an integrated coil resonator to drive coherent single- and two-qubit gates with \Sr optical qubits. We measure an average single-qubit fidelity of $99.61\%\pm 0.03\%$ per Clifford gate with randomized benchmarking and use a two-qubit Mølmer-Sørensen interaction to generate an entangled Bell state with a fidelity of $92.35\% \pm 1.50\%$. The qubit exhibits a bare Ramsey coherence time of $659 \pm 9~μ$s, more than a tenfold improvement over our previous implementation, which extends to $1.750 \pm 0.033$~ms with an echo. These results demonstrate, for the first time, that integrated visible-wavelength narrow-linewidth photonic lasers can meet the phase-noise requirements for coherent quantum logic with trapped ion optical qubits, providing a path for scalable optical systems integrated within trapped ion quantum processors.

quant-pharXiv:2609.07708•Sep 8, 2026•0 citations

High-fidelity ion-trap quantum computing with hyperfine clock states

Leandro Aolita, Kihwan Kim, Jan Benhelm +2 more

We propose the implementation of a geometric-phase gate on magnetic-field-insensitive qubits with ${\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\ensuremath{\sigma}}}^{z}$-dependent forces for trapped ion quantum computing. The force is exerted by two laser beams in a Raman configuration. Qubit-state dependency is achieved by a small frequency detuning from the virtually excited state. Ion species with excited states of long radiative lifetimes are used to reduce the chance of a spontaneous photon emission to less than ${10}^{\ensuremath{-}8}\phantom{\rule{0.3em}{0ex}}\mathrm{per}$ gate run. This eliminates the main source of gate infidelity in previous implementations. With this scheme it seems possible to reach the fault-tolerant threshold.

arXiv:0707.3916•Physical Review A•Oct 19, 2007•21 citations

Entanglement of trapped-ion clock states

P. C. Haljan, P. J. Lee, Kathy-Anne Brickman +3 more

A M\o{}lmer-S\o{}rensen entangling gate is realized for pairs of trapped $^{111}\mathrm{Cd}^{+}$ ions using magnetic-field insensitive ``clock'' states and an implementation offering reduced sensitivity to optical phase drifts. The gate is used to generate the complete set of four entangled states, which are reconstructed and evaluated with quantum-state tomography. An average target-state fidelity of 0.79 is achieved, limited by available laser power and technical noise. The tomographic reconstruction of entangled states demonstrates universal quantum control of two ion qubits, which through multiplexing can provide a route to scalable architectures for trapped-ion quantum computing.

arXiv:quant-ph/0508123•Physical Review A•Dec 9, 2005•124 citations
To date, the highest-fidelity quantum logic gates between two qubits have been achieved using the geometric-phase gate in trapped ions, with the two leading variants being the M\o{}lmer-S\o{}rensen gate and the light-shift (LS) gate. Both of these approaches have their respective advantages and challenges. For example, the latter is technically simpler and is natively insensitive to optical phases, but it has not been made to work directly on a clock-state qubit. We present a technique for implementing the LS gate that combines the best features of these two approaches: By using a small (\ensuremath∼MHz\ensuremath{\sim}\mathrm{MHz}\ensuremath∼MHz) detuning from a narrow (dipole-forbidden) optical transition, we are able to operate an LS gate directly on hyperfine clock states, achieving gate fidelities of 99.74(4)99.74(4)%99.74(4) using modest laser power at visible wavelengths. Current gate infidelities appear to be dominated by technical noise, and theoretical modeling suggests a path toward gate fidelity above 99.9999.99%99.99.
Entanglement generation in trapped-ion systems has relied thus far on two distinct but related geometric phase gate techniques: Mølmer-Sørensen and light-shift gates. We recently proposed a variant of the light-shift scheme where the qubit levels are separated by an optical frequency [B. C. Sawyer and K. R. Brown, Phys. Rev. A 103, 022427 (2021)PLRAAN2469-992610.1103/PhysRevA.103.022427]. Here we report an experimental demonstration of this entangling gate using a pair of ^{40}Ca^{+} ions in a cryogenic surface-electrode ion trap and a commercial, high-power, 532 nm Nd:YAG laser. Generating a Bell state in 35 μs, we directly measure an infidelity of 6(3)×10^{-4} without subtraction of experimental errors. The 532 nm gate laser wavelength suppresses intrinsic photon scattering error to ∼1×10^{-5}.
High-fidelity and parallel realization in scalable platforms of the two-qubit entangling gates fundamental to universal quantum computing constitutes one of the largest challenges in implementing fault-tolerant quantum computation. Integrated optical addressing of trapped-ion qubits offers routes to scaling the high-fidelity optical control demonstrated to date in small systems. Here we show that in addition to scaling, capabilities practically enabled by integrated optics can substantially alleviate laser powers required for both light-shift (LS) and Molmer-Sorensen (MS) geometric phase gates acting on long-lived ground-state qubit encodings in a broad range of ion species. In the proposed gate schemes utilizing carrier nulling via ion positioning at phase-stable standing-wave (SW) nodes, our calculations suggest that suppressed spontaneous photon scattering at the SW node allows for gate drives operating at smaller Raman detunings, resulting in approximately an order-of-magnitude reduction in power requirement (and significantly larger in certain parameter regimes) for gates of a given duration and scattering-limited fidelity as compared to conventional running wave (RW)-based approaches. The SW schemes have the additional benefit of simultaneously eliminating undesired coherent couplings that typically limit gate speeds. Our work quantifies power requirements for multiple ion species and enhancements to be expected from carrier-nulled configurations practically enabled by integrated delivery, and informs experiments and systems for realization of fast and power-efficient laser-based entangling gates in scalable platforms.
We demonstrate laser-driven two-qubit and single-qubit logic gates with respective fidelities 99.9(1)% and 99.9934(3)%, significantly above the ≈99% minimum threshold level required for fault-tolerant quantum computation, using qubits stored in hyperfine ground states of calcium-43 ions held in a room-temperature trap. We study the speed-fidelity trade-off for the two-qubit gate, for gate times between 3.8 μs and 520 μs, and develop a theoretical error model which is consistent with the data and which allows us to identify the principal technical sources of infidelity.
Trapped ions are a leading technology for quantum computing, but their reliance on bespoke tabletop laser and optical systems remains a major obstacle to scaling and robustness. Integrated silicon nitride lasers, compatible with future monolithic integration with surface electrode ion traps, have recently demonstrated frequency-selective qubit state preparation and measurement as well as interrogation of an optical clock transition. However, coherent qubit gates impose even more stringent requirements on laser phase noise, and their implementation with integrated laser sources has remained an outstanding challenge. Here, we use a visible-wavelength integrated Brillouin laser stabilized to an integrated coil resonator to drive coherent single- and two-qubit gates with \Sr optical qubits. We measure an average single-qubit fidelity of 99.61%±0.03%99.61\%\pm 0.03\%99.61%±0.03% per Clifford gate with randomized benchmarking and use a two-qubit Mølmer-Sørensen interaction to generate an entangled Bell state with a fidelity of 92.35%±1.50%92.35\% \pm 1.50\%92.35%±1.50%. The qubit exhibits a bare Ramsey coherence time of 659±9 μ659 \pm 9~μ659±9 μs, more than a tenfold improvement over our previous implementation, which extends to 1.750±0.0331.750 \pm 0.0331.750±0.033~ms with an echo. These results demonstrate, for the first time, that integrated visible-wavelength narrow-linewidth photonic lasers can meet the phase-noise requirements for coherent quantum logic with trapped ion optical qubits, providing a path for scalable optical systems integrated within trapped ion quantum processors.
We propose the implementation of a geometric-phase gate on magnetic-field-insensitive qubits with ${\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\ensuremath{\sigma}}}^{z}$-dependent forces for trapped ion quantum computing. The force is exerted by two laser beams in a Raman configuration. Qubit-state dependency is achieved by a small frequency detuning from the virtually excited state. Ion species with excited states of long radiative lifetimes are used to reduce the chance of a spontaneous photon emission to less than ${10}^{\ensuremath{-}8}\phantom{\rule{0.3em}{0ex}}\mathrm{per}$ gate run. This eliminates the main source of gate infidelity in previous implementations. With this scheme it seems possible to reach the fault-tolerant threshold.
A M\o{}lmer-S\o{}rensen entangling gate is realized for pairs of trapped 111Cd+^{111}\mathrm{Cd}^{+}111Cd+ ions using magnetic-field insensitive ``clock'' states and an implementation offering reduced sensitivity to optical phase drifts. The gate is used to generate the complete set of four entangled states, which are reconstructed and evaluated with quantum-state tomography. An average target-state fidelity of 0.79 is achieved, limited by available laser power and technical noise. The tomographic reconstruction of entangled states demonstrates universal quantum control of two ion qubits, which through multiplexing can provide a route to scalable architectures for trapped-ion quantum computing.