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:0807.0797 · Physical Review B

Landau-Zener transitions in a superconducting flux qubit

J. Johansson, M. H. S. Amin, A. J. Berkley, P. Bunyk, Vicky Choi, R. Harris, Mark W. Johnson, Trevor M. Lanting, Seth Lloyd, Geordie Rose

Published Jul 21, 2009• 34 citations
arXivHTMLPDF

Abstract

We report an experimental measurement of Landau-Zener transitions on an individual flux qubit within a multiqubit superconducting chip. The method used isolates a single qubit, tunes its tunneling amplitude $\ensuremath{\Delta}$ into the limit where $\ensuremath{\Delta}$ is much less than both the temperature $T$ and the decoherence-induced energy level broadening, and forces it to undergo a Landau-Zener transition. We find that the behavior of the qubit agrees to a high degree of accuracy with theoretical predictions for Landau-Zener transition probabilities for a double-well quantum system coupled to a nonMarkovian $1/f$ magnetic flux noise.

DOI
10.1103/physrevb.80.012507

Related papers

Landau-Zener-Stuckelberg interferometry in multilevel superconducting flux qubit

Xueda Wen, Yiwen Wang, Shanhua Cong +7 more

Landau-Zener-Stuckelberg interferometry has been extensively investigated in quantum two-level systems, with particular interests on artificial system such as superconducting flux qubits. With increasing the driving field amplitude, more energy levels will be involved into the quantum evolution, which results in population inversion and many interesting interference patterns. These interference patterns can be used to obtain the parameters characterizing the system and probe dephasing mechanisms of the qubit. Most recently, experiments have been extended to the regime with higher-frequency and larger-amplitude driving field, in which the interference pattern exhibited more complicated characteristics. In this article, we give a universal description of the characteristics observed in both low-frequency and high-frequency regimes. Besides explaining the already observed experimental results, our theoretical model predicted many interesting phenomenon, which can be demonstrated by future experiments.

arXiv:1003.2025•Mar 10, 2010•2 citations

Observation of 65 GHz Coherent Oscillation in a Superconducting Flux Qubit Manipulated by Pulses

F. Chiarello, P. Carelli, Maria Gabriella Castellano +2 more

A superconducting flux qubit can be manipulated by a fast modification of its potential, with a rapid transition from a double well to a single well shape, and coming back to the initial condition. This mechanism is based on a non-trivial quantum phenomenon, involving "partial" Landau-Zener transitions, coherent evolution in an harmonic potential and quantum interference. The study of this system enables a deep insight in decoherence mechanisms typical of superconducting qubits. Moreover, this procedure allows quantum operations with extreme high speeds, not possible with other standard manipulations. We present the experimental observation of coherent oscillations showing tunable frequencies with a 65 GHz top value. © Published under licence by IOP Publishing Ltd.

Journal of Physics Conference Series•May 12, 2014•0 citations

Landau-Zener-Stückelberg spectroscopy of a superconducting flux qubit

Shuang Xu, Yang Yu, Guozhu Sun

We proposed a different method to measure the energy spectrum of a superconducting flux qubit. Different from the conventional frequency spectroscopy, a linear triangle pulse was used to drive the qubit through the anticrossing and to generate Landau-Zener-St\"uckelberg interference patterns, from which the information of the energy spectrum can be extracted. This method facilitates the spectroscopy in regimes of very large energies. Moreover, without installing microwaves lines one can simplify the experimental setup and reduce the unwanted effects of noise. The idea can be applied to other quantum systems as well, opening the possibility of calibrating and manipulating qubits with linear pulses.

arXiv:1009.4295•Physical Review B•Oct 27, 2010•8 citations

Resonant effects in a SQUID qubit subjected to nonadiabatic changes

F. Chiarello, Samuele Spilla, Maria Gabriella Castellano +5 more

By quickly modifying the shape of the effective potential of a double SQUID flux qubit from a single-well to a double-well condition, we experimentally observe an anomalous behavior, namely, an alternation of resonance peaks, in the probability to find the qubit in a given flux state. The occurrence of Landau-Zener transitions as well as resonant tunneling between degenerate levels in the two wells may be invoked to partially justify the experimental results. A quantum simulation of the time evolution of the system indeed suggests that the observed anomalous behavior can be imputable to quantum coherence effects. The interplay among all these mechanisms has a practical implication for quantum computing purposes, giving a direct measurement of the limits on the sweeping rates possible for a correct manipulation of the qubit state by means of fast flux pulses, avoiding transitions to noncomputational states.

arXiv:1310.5491•Physical Review B•Apr 11, 2014•1 citation

Dissipative Landau-Zener transitions of a qubit: Bath-specific and universal behavior

Keiji Saito, Martijn Wubs, Sigmund Kohler +2 more

We study Landau-Zener transitions in a qubit coupled to a bath at zero temperature. A general formula that is applicable to models with a nondegenerate ground state is derived. We calculate exact transition probabilities for a qubit coupled to either a bosonic or a spin bath. The nature of the baths and the qubit-bath coupling is reflected in the transition probabilities. For diagonal coupling, when the bath causes energy fluctuations of the diabatic qubit states but no transitions between them, the transition probability coincides with the standard Landau-Zener probability of an isolated qubit. This result is universal as it does not depend on the specific type of bath. For pure off-diagonal coupling, by contrast, the tunneling probability is sensitive to the coupling strength. We discuss the relevance of our results for experiments on molecular nanomagnets, in circuit QED, and for the fast-pulse readout of superconducting phase qubits.

arXiv:cond-mat/0703596•Physical Review B•Jun 29, 2007•142 citations

Dissipative Landau-Zener tunneling in the crossover regime from weak to strong environment coupling

Xi Dai, Robbyn Trappen, Huo Chen +22 more

Landau-Zener tunneling, which describes the transition in a two-level system during a sweep through an anti-crossing, is a model applicable to a wide range of physical phenomena. Realistic quantum systems are affected by dissipation due to coupling to their environments. An important aspect of understanding such open quantum systems is the relative energy scales of the system itself and the system-environment coupling, which distinguishes the weak- and strong-coupling regimes. Using a tunable superconducting flux qubit, we observe the crossover from weak to strong coupling to the environment in Landau-Zener tunneling. Our results confirm previous theoretical studies of dissipative Landau-Zener tunneling in the weak and strong coupling limits. We devise a spin bath model that effectively captures the crossover regime. This work is relevant for understanding the role of dissipation in quantum annealing, where the system is expected to go through a cascade of Landau-Zener transitions before reaching the target state.

arXiv:2207.02017•Nature Communications•Jan 2, 2025•8 citations
We report an experimental measurement of Landau-Zener transitions on an individual flux qubit within a multiqubit superconducting chip. The method used isolates a single qubit, tunes its tunneling amplitude \ensuremathΔ\ensuremath{\Delta}\ensuremathΔ into the limit where \ensuremathΔ\ensuremath{\Delta}\ensuremathΔ is much less than both the temperature TTT and the decoherence-induced energy level broadening, and forces it to undergo a Landau-Zener transition. We find that the behavior of the qubit agrees to a high degree of accuracy with theoretical predictions for Landau-Zener transition probabilities for a double-well quantum system coupled to a nonMarkovian 1/f1/f1/f magnetic flux noise.
Landau-Zener-Stuckelberg interferometry has been extensively investigated in quantum two-level systems, with particular interests on artificial system such as superconducting flux qubits. With increasing the driving field amplitude, more energy levels will be involved into the quantum evolution, which results in population inversion and many interesting interference patterns. These interference patterns can be used to obtain the parameters characterizing the system and probe dephasing mechanisms of the qubit. Most recently, experiments have been extended to the regime with higher-frequency and larger-amplitude driving field, in which the interference pattern exhibited more complicated characteristics. In this article, we give a universal description of the characteristics observed in both low-frequency and high-frequency regimes. Besides explaining the already observed experimental results, our theoretical model predicted many interesting phenomenon, which can be demonstrated by future experiments.
A superconducting flux qubit can be manipulated by a fast modification of its potential, with a rapid transition from a double well to a single well shape, and coming back to the initial condition. This mechanism is based on a non-trivial quantum phenomenon, involving "partial" Landau-Zener transitions, coherent evolution in an harmonic potential and quantum interference. The study of this system enables a deep insight in decoherence mechanisms typical of superconducting qubits. Moreover, this procedure allows quantum operations with extreme high speeds, not possible with other standard manipulations. We present the experimental observation of coherent oscillations showing tunable frequencies with a 65 GHz top value. © Published under licence by IOP Publishing Ltd.
We proposed a different method to measure the energy spectrum of a superconducting flux qubit. Different from the conventional frequency spectroscopy, a linear triangle pulse was used to drive the qubit through the anticrossing and to generate Landau-Zener-St\"uckelberg interference patterns, from which the information of the energy spectrum can be extracted. This method facilitates the spectroscopy in regimes of very large energies. Moreover, without installing microwaves lines one can simplify the experimental setup and reduce the unwanted effects of noise. The idea can be applied to other quantum systems as well, opening the possibility of calibrating and manipulating qubits with linear pulses.
By quickly modifying the shape of the effective potential of a double SQUID flux qubit from a single-well to a double-well condition, we experimentally observe an anomalous behavior, namely, an alternation of resonance peaks, in the probability to find the qubit in a given flux state. The occurrence of Landau-Zener transitions as well as resonant tunneling between degenerate levels in the two wells may be invoked to partially justify the experimental results. A quantum simulation of the time evolution of the system indeed suggests that the observed anomalous behavior can be imputable to quantum coherence effects. The interplay among all these mechanisms has a practical implication for quantum computing purposes, giving a direct measurement of the limits on the sweeping rates possible for a correct manipulation of the qubit state by means of fast flux pulses, avoiding transitions to noncomputational states.
We study Landau-Zener transitions in a qubit coupled to a bath at zero temperature. A general formula that is applicable to models with a nondegenerate ground state is derived. We calculate exact transition probabilities for a qubit coupled to either a bosonic or a spin bath. The nature of the baths and the qubit-bath coupling is reflected in the transition probabilities. For diagonal coupling, when the bath causes energy fluctuations of the diabatic qubit states but no transitions between them, the transition probability coincides with the standard Landau-Zener probability of an isolated qubit. This result is universal as it does not depend on the specific type of bath. For pure off-diagonal coupling, by contrast, the tunneling probability is sensitive to the coupling strength. We discuss the relevance of our results for experiments on molecular nanomagnets, in circuit QED, and for the fast-pulse readout of superconducting phase qubits.
Landau-Zener tunneling, which describes the transition in a two-level system during a sweep through an anti-crossing, is a model applicable to a wide range of physical phenomena. Realistic quantum systems are affected by dissipation due to coupling to their environments. An important aspect of understanding such open quantum systems is the relative energy scales of the system itself and the system-environment coupling, which distinguishes the weak- and strong-coupling regimes. Using a tunable superconducting flux qubit, we observe the crossover from weak to strong coupling to the environment in Landau-Zener tunneling. Our results confirm previous theoretical studies of dissipative Landau-Zener tunneling in the weak and strong coupling limits. We devise a spin bath model that effectively captures the crossover regime. This work is relevant for understanding the role of dissipation in quantum annealing, where the system is expected to go through a cascade of Landau-Zener transitions before reaching the target state.