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

Journal of Physics B Atomic Molecular and Optical Physics

Extending the DRAG method to Landau–Zener control via isoprobability twin models

Ivo S. Mihov, Nikolay V. Vitanov

Published Sep 30, 2026• 0 citations
Publisher

Abstract

Abstract The Derivative Removal by Adiabatic Gate (DRAG) technique is the standard remedy for leakage to non-computational states in transmon-based quantum gates. However, a wide class of platforms—including fluxonium and composite-transmon qubits—cannot benefit from it, since their canonical gate implementations rely on Landau-Majorana-Stückelberg-Zener (LMSZ) protocols. Specifically, the constant Rabi envelope of the LMSZ model does not allow using the DRAG correction, which requires a non-zero first derivative. A complementary obstruction affects hardware that does not support time-dependent Rabi-frequency modulation: such platforms cannot benefit from the Allen-Eberly-Hioe (AEH) model either, an unpleasant fact given its analytical tractability. We resolve both limitations by introducing the concept of isoprobability twin models—distinct pairs of Rabi frequency Ω ( t ) and detuning Δ ( t ) that yield identical post-pulse transition probabilities through the Delos–Thorson transformation. We experimentally demonstrate the equivalence of multiple LMSZ and AEH twin models on IBM’s ibm_kyiv processor. We then show that the framework unlocks the DRAG technique by trading the canonical, constant-Rabi LMSZ pulse for a smooth cosine-Rabi twin, and numerically demonstrate that the resulting DRAG-corrected pulse suppresses leakage to a transmon’s non-computational states by up to six orders of magnitude at moderate chirp slopes and by three orders of magnitude on average over the entire driving landscape, while preserving the LMSZ transition-probability landscape.

DOI
10.1088/1361-6455/aeae8c

Related papers

DRAG-Compatible Leakage Suppression in Landau--Zener Control via Isoprobability Twins

Ivo S. Mihov, Nikolay V. Vitanov

Analytically solvable models -- particularly the Landau-Majorana-Stückelberg-Zener (LMSZ) and Allen-Eberly-Hioe (AEH) models -- underpin many quantum-gate implementations and population-transfer protocols. However, their canonical pulse shapes are incompatible with modern leakage-suppression techniques and some systems. Most notably, the constant Rabi envelope of the LMSZ pulse prevents many leakage-suppression approaches, which require smoothness. We address both limitations by developing the concept of isoprobability twin models: distinct pairs of Rabi frequency $Ω(t)$ and detuning $Δ(t)$ that yield identical post-pulse transition probabilities based on the Delos-Thorson transformation. In this work, we formalise the method by experimentally demonstrating the equivalence of multiple LMSZ and AEH twin models on IBM's ibm_kyiv processor. Finally, we show a staggering leakage reduction by more than 3 orders of magnitude using a custom DRAG implementation of a cosine LMSZ isoprobability model.

arXiv:2506.19572•Jun 24, 2025•0 citations

Reducing Leakage of Single-Qubit Gates for Superconducting Quantum Processors Using Analytical Control Pulse Envelopes

Eric Hyyppä, Antti P. Vepsäläinen, Miha Papič +10 more

Improving the speed and fidelity of quantum logic gates is essential to reach quantum advantage with future quantum computers. However, fast logic gates lead to increased leakage errors in superconducting quantum processors based on qubits with low anharmonicity, such as transmons. To reduce leakage errors, we propose and experimentally demonstrate two new analytical methods, Fourier ansatz spectrum tuning derivative removal by adiabatic gate (FAST DRAG) and higher-derivative (HD) DRAG, both of which enable shaping single-qubit control pulses in the frequency domain to achieve stronger suppression of leakage transitions compared to previously demonstrated pulse shapes. Using the new methods to suppress the e f transition of a transmon qubit with an anharmonicity of − 212 MHz, we implement R X ( π / 2 ) gates achieving a leakage error below 3.0 × 10 − 5 down to a gate duration of 6.25 ns without the need for iterative closed-loop optimization. The obtained leakage error represents a 20-fold reduction in leakage compared to a conventional cosine DRAG pulse. Employing the FAST DRAG method, we further achieve an error per gate of ( 1.56 ± 0.07 ) × 10 − 4 at a 7.9-ns gate duration, outperforming conventional pulse shapes both in terms of error and gate speed. Furthermore, we study error-amplifying measurements for the characterization of temporal microwave control-pulse distortions, and demonstrate that non-Markovian coherent errors caused by such distortions may be a significant source of error for sub-10-ns single-qubit gates unless corrected using predistortion. Published by the American Physical Society 2024

arXiv:2402.17757•PRX Quantum•Sep 19, 2024•67 citations

Separate Control of Transient Leakage Exposure and Endpoint Leakage in Fast Transmon Gates

Haoran Yang, Fudong Liu, Weilong Wang +2 more

Leakage to noncomputational states limits the speed of single-qubit gates in weakly anharmonic transmons. Conventional pulse-shaping methods, including derivative removal by adiabatic gate (DRAG), primarily suppress the leakage remaining at the end of a gate. Here we demonstrate that endpoint leakage and the transient leakage population that accumulates during the gate represent distinct control objectives. Endpoint leakage is associated with the drive spectrum at the anharmonicity, whereas transient exposure depends on spectral weight over a finite frequency band and governs the additional leakage induced by dephasing. A spectral null at the leakage transition therefore suppresses the endpoint amplitude without necessarily reducing transient exposure. Based on this distinction, we introduce a path--endpoint separation pulse that combines transient-path shaping with a two-tone endpoint correction. For a $10$ ns $R_X(π/2)$ gate with an anharmonicity magnitude of $0.2$ GHz, numerical simulations show a $21\%$ reduction in transient exposure relative to cosine DRAG and a corresponding $20\%$ reduction in dephasing-induced excess leakage. The two correction tones further suppress residual leakage through the $|2\rangle$ and $|3\rangle$ channels, lowering the coherent endpoint leakage from approximately $7\times10^{-7}$ to $3\times10^{-8}$ without increasing transient exposure. These results establish transient exposure and endpoint leakage as complementary targets for the design of fast transmon gates.

quant-pharXiv:2607.05779•Jul 8, 2026•0 citations

Analytic leakage suppression with a single control field: fast two-qubit gates with tunable couplers

Lukas Heunisch, Michael J. Hartmann, Aashish A. Clerk

Simple analytic pulse-shaping techniques are of great practical utility in quantum control, with prime examples being the DRAG method for suppressing leakage in superconducting microwave gates and the transitionless-driving approach to shortcuts-to-adiabaticity. Standard versions of these methods require two orthogonal control channels, with the second channel effectively breaking time-reversal symmetry. This appears to rule out their use in settings with only a single real-valued control field, such as the kind of baseband flux control that is common in many superconducting circuit architectures. We show here that a simple analytic pulse-shaping technique derived via a Magnus expansion is effective even with just a single baseband control channel. We demonstrate its efficacy by simulating a two-qubit gate between transmons realized with a tunable coupler and baseband flux pulses. Our corrections dramatically reduce non-adiabatic leakage caused by ramping the coupler: for realistic device parameters, leakage in a fast iSWAP gate is suppressed by up to three orders of magnitude. Our approach is general, goes beyond simply suppressing unwanted spectral weight at leakage transitions, and can be applied to a variety of platforms.

quant-pharXiv:2609.20766•Sep 18, 2026•0 citations

Alternative fast quantum logic gates using nonadiabatic Landau-Zener-Stückelberg-Majorana transitions

A. I. Ryzhov, O. V. Ivakhnenko, Sergey N Shevchenko +2 more

A conventional realization of quantum logic gates and control is based on resonant Rabi oscillations of the occupation probability of the system. This approach has certain limitations and complications, like counter-rotating terms. We study an alternative paradigm for implementing quantum logic gates based on Landau-Zener-Stückelberg-Majorana (LZSM) interferometry with nonresonant driving and the alternation of adiabatic evolution and nonadiabatic transitions. Compared to Rabi oscillations, the main differences are a nonresonant driving frequency and a small number of periods in the external driving. We explore the dynamics of a multilevel quantum system under LZSM drives and optimize the parameters for increasing the gate speed. We define the parameters of the external driving required for implementing a specific quantum logic gate using the adiabatic-impulse model. In particular, we demonstrate the implementations of single-qubit X, Y, Hadamard gates, and two-qubit i and gates using the LZSM transitions. The considered LZSM approach for implementing arbitrary quantum logic gates can be applied to a large variety of multilevel quantum systems and external driving. Published by the American Physical Society 2024

arXiv:2310.17932•Physical Review Research•Sep 26, 2024•15 citations

Simple analytical flux-tuned iSWAP pulses for leakage suppression

Dimitrios Georgiadis, Boxi Li, Asier Galicia +3 more

Fast, high-fidelity two-qubit gates are a key requirement for fault-tolerant quantum computation. Tunable coupler architectures provide a flexible approach for implementing entangling gates through flux control with large on-off ratios, but fast flux modulation can induce diabatic transitions and population leakage to non-computational states, limiting gate performance. Here we present an analytical flux control method enabling derivative removal by adiabatic gate ($Φ$-DRAG) for suppressing leakage in flux tunable two-qubit gates. We show that $Φ$-DRAG differs fundamentally from conventional microwave implementations and derive modified flux modulation protocols that suppress leakage below $10^{-4}$ for fast entangling gates. The method remains effective across a range of asymmetry between qubit anharmonicities and different circuit parameters, enabling high-fidelity two-qubit gates within the fifteen nanosecond range.

quant-pharXiv:2606.13052•Jun 12, 2026•0 citations
Abstract The Derivative Removal by Adiabatic Gate (DRAG) technique is the standard remedy for leakage to non-computational states in transmon-based quantum gates. However, a wide class of platforms—including fluxonium and composite-transmon qubits—cannot benefit from it, since their canonical gate implementations rely on Landau-Majorana-Stückelberg-Zener (LMSZ) protocols. Specifically, the constant Rabi envelope of the LMSZ model does not allow using the DRAG correction, which requires a non-zero first derivative. A complementary obstruction affects hardware that does not support time-dependent Rabi-frequency modulation: such platforms cannot benefit from the Allen-Eberly-Hioe (AEH) model either, an unpleasant fact given its analytical tractability. We resolve both limitations by introducing the concept of isoprobability twin models—distinct pairs of Rabi frequency Ω ( t ) and detuning Δ ( t ) that yield identical post-pulse transition probabilities through the Delos–Thorson transformation. We experimentally demonstrate the equivalence of multiple LMSZ and AEH twin models on IBM’s ibm_kyiv processor. We then show that the framework unlocks the DRAG technique by trading the canonical, constant-Rabi LMSZ pulse for a smooth cosine-Rabi twin, and numerically demonstrate that the resulting DRAG-corrected pulse suppresses leakage to a transmon’s non-computational states by up to six orders of magnitude at moderate chirp slopes and by three orders of magnitude on average over the entire driving landscape, while preserving the LMSZ transition-probability landscape.
Analytically solvable models -- particularly the Landau-Majorana-Stückelberg-Zener (LMSZ) and Allen-Eberly-Hioe (AEH) models -- underpin many quantum-gate implementations and population-transfer protocols. However, their canonical pulse shapes are incompatible with modern leakage-suppression techniques and some systems. Most notably, the constant Rabi envelope of the LMSZ pulse prevents many leakage-suppression approaches, which require smoothness. We address both limitations by developing the concept of isoprobability twin models: distinct pairs of Rabi frequency Ω(t)Ω(t)Ω(t) and detuning Δ(t)Δ(t)Δ(t) that yield identical post-pulse transition probabilities based on the Delos-Thorson transformation. In this work, we formalise the method by experimentally demonstrating the equivalence of multiple LMSZ and AEH twin models on IBM's ibm_kyiv processor. Finally, we show a staggering leakage reduction by more than 3 orders of magnitude using a custom DRAG implementation of a cosine LMSZ isoprobability model.
Improving the speed and fidelity of quantum logic gates is essential to reach quantum advantage with future quantum computers. However, fast logic gates lead to increased leakage errors in superconducting quantum processors based on qubits with low anharmonicity, such as transmons. To reduce leakage errors, we propose and experimentally demonstrate two new analytical methods, Fourier ansatz spectrum tuning derivative removal by adiabatic gate (FAST DRAG) and higher-derivative (HD) DRAG, both of which enable shaping single-qubit control pulses in the frequency domain to achieve stronger suppression of leakage transitions compared to previously demonstrated pulse shapes. Using the new methods to suppress the e f transition of a transmon qubit with an anharmonicity of − 212 MHz, we implement R X ( π / 2 ) gates achieving a leakage error below 3.0 × 10 − 5 down to a gate duration of 6.25 ns without the need for iterative closed-loop optimization. The obtained leakage error represents a 20-fold reduction in leakage compared to a conventional cosine DRAG pulse. Employing the FAST DRAG method, we further achieve an error per gate of ( 1.56 ± 0.07 ) × 10 − 4 at a 7.9-ns gate duration, outperforming conventional pulse shapes both in terms of error and gate speed. Furthermore, we study error-amplifying measurements for the characterization of temporal microwave control-pulse distortions, and demonstrate that non-Markovian coherent errors caused by such distortions may be a significant source of error for sub-10-ns single-qubit gates unless corrected using predistortion. Published by the American Physical Society 2024
Leakage to noncomputational states limits the speed of single-qubit gates in weakly anharmonic transmons. Conventional pulse-shaping methods, including derivative removal by adiabatic gate (DRAG), primarily suppress the leakage remaining at the end of a gate. Here we demonstrate that endpoint leakage and the transient leakage population that accumulates during the gate represent distinct control objectives. Endpoint leakage is associated with the drive spectrum at the anharmonicity, whereas transient exposure depends on spectral weight over a finite frequency band and governs the additional leakage induced by dephasing. A spectral null at the leakage transition therefore suppresses the endpoint amplitude without necessarily reducing transient exposure. Based on this distinction, we introduce a path--endpoint separation pulse that combines transient-path shaping with a two-tone endpoint correction. For a 101010 ns RX(π/2)R_X(π/2)RX​(π/2) gate with an anharmonicity magnitude of 0.20.20.2 GHz, numerical simulations show a 21%21\%21% reduction in transient exposure relative to cosine DRAG and a corresponding 20%20\%20% reduction in dephasing-induced excess leakage. The two correction tones further suppress residual leakage through the ∣2⟩|2\rangle∣2⟩ and ∣3⟩|3\rangle∣3⟩ channels, lowering the coherent endpoint leakage from approximately 7×10−77\times10^{-7}7×10−7 to 3×10−83\times10^{-8}3×10−8 without increasing transient exposure. These results establish transient exposure and endpoint leakage as complementary targets for the design of fast transmon gates.
Simple analytic pulse-shaping techniques are of great practical utility in quantum control, with prime examples being the DRAG method for suppressing leakage in superconducting microwave gates and the transitionless-driving approach to shortcuts-to-adiabaticity. Standard versions of these methods require two orthogonal control channels, with the second channel effectively breaking time-reversal symmetry. This appears to rule out their use in settings with only a single real-valued control field, such as the kind of baseband flux control that is common in many superconducting circuit architectures. We show here that a simple analytic pulse-shaping technique derived via a Magnus expansion is effective even with just a single baseband control channel. We demonstrate its efficacy by simulating a two-qubit gate between transmons realized with a tunable coupler and baseband flux pulses. Our corrections dramatically reduce non-adiabatic leakage caused by ramping the coupler: for realistic device parameters, leakage in a fast iSWAP gate is suppressed by up to three orders of magnitude. Our approach is general, goes beyond simply suppressing unwanted spectral weight at leakage transitions, and can be applied to a variety of platforms.
A conventional realization of quantum logic gates and control is based on resonant Rabi oscillations of the occupation probability of the system. This approach has certain limitations and complications, like counter-rotating terms. We study an alternative paradigm for implementing quantum logic gates based on Landau-Zener-Stückelberg-Majorana (LZSM) interferometry with nonresonant driving and the alternation of adiabatic evolution and nonadiabatic transitions. Compared to Rabi oscillations, the main differences are a nonresonant driving frequency and a small number of periods in the external driving. We explore the dynamics of a multilevel quantum system under LZSM drives and optimize the parameters for increasing the gate speed. We define the parameters of the external driving required for implementing a specific quantum logic gate using the adiabatic-impulse model. In particular, we demonstrate the implementations of single-qubit X, Y, Hadamard gates, and two-qubit i and gates using the LZSM transitions. The considered LZSM approach for implementing arbitrary quantum logic gates can be applied to a large variety of multilevel quantum systems and external driving. Published by the American Physical Society 2024
Fast, high-fidelity two-qubit gates are a key requirement for fault-tolerant quantum computation. Tunable coupler architectures provide a flexible approach for implementing entangling gates through flux control with large on-off ratios, but fast flux modulation can induce diabatic transitions and population leakage to non-computational states, limiting gate performance. Here we present an analytical flux control method enabling derivative removal by adiabatic gate (ΦΦΦ-DRAG) for suppressing leakage in flux tunable two-qubit gates. We show that ΦΦΦ-DRAG differs fundamentally from conventional microwave implementations and derive modified flux modulation protocols that suppress leakage below 10−410^{-4}10−4 for fast entangling gates. The method remains effective across a range of asymmetry between qubit anharmonicities and different circuit parameters, enabling high-fidelity two-qubit gates within the fifteen nanosecond range.