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:1201.6341 · Physical Review Letters

Driven Dynamics and Rotary Echo of a Qubit Tunably Coupled to a Harmonic Oscillator

Simon Gustavsson, Jonas Bylander, F. Yan, P. Forn-Díaz, Vladimir Bolkhovsky, Danielle Braje, George Fitch, K. Harrabi, Donna M. Lennon, Jovi Miloshi, P. Murphy, Richard L. Slattery, S. J. Spector, Ben Turek, Terence J. Weir, Paul B. Welander, Fumiki Yoshihara, David G. Cory, Yasunobu Nakamura, Terry P. Orlando, William D. Oliver

Published Apr 27, 2012• 31 citations
arXivHTMLPDF

Abstract

We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.

DOI
10.1103/physrevlett.108.170503

Related papers

Flux qubit noise spectroscopy using Rabi oscillations under strong driving conditions

Fumiki Yoshihara, Yasunobu Nakamura, Fei Yan +4 more

We infer the high-frequency flux noise spectrum in a superconducting flux qubit by studying the decay of Rabi oscillations under strong driving conditions. The large anharmonicity of the qubit and its strong inductive coupling to a microwave line enabled high-amplitude driving without causing significant additional decoherence. Rabi frequencies up to 1.7 GHz were achieved, approaching the qubit's level splitting of 4.8 GHz, a regime where the rotating-wave approximation breaks down as a model for the driven dynamics. The spectral density of flux noise observed in the wide frequency range decreases with increasing frequency up to 300 MHz, where the spectral density is not very far from the extrapolation of the $1/f$ spectrum obtained from the free-induction-decay measurements. We discuss a possible origin of the flux noise due to surface electron spins.

arXiv:1402.1247•Physical Review B•Jan 9, 2014•95 citations

Transmission spectra of the driven, dissipative Rabi model in the ultrastrong-coupling regime

Luca Magazzù, P. Forn-Díaz, Milena Grifoni

We present theoretical transmission spectra of a strongly driven, damped flux qubit coupled to a dissipative resonator in the ultrastrong-coupling regime. Such a qubit-oscillator system, described within a dissipative Rabi model, constitutes the building block of superconducting circuit QED platforms. The addition of a strong drive allows one to characterize the system properties and study novel phenomena, leading to a better understanding and control of the qubit-oscillator system. In this work, the calculated transmission of a weak probe field quantifies the response of the qubit, in frequency domain, under the influence of the quantized resonator and of the strong microwave drive. We find distinctive features of the entangled driven qubit-resonator spectrum, namely resonant features and avoided crossings, modified by the presence of the dissipative environment. The magnitude, positions, and broadening of these features are determined by the interplay among qubit-oscillator detuning, the strength of their coupling, the driving amplitude, and the interaction with the heat bath. This work establishes the theoretical basis for future experiments in the driven ultrastrong-coupling regime.

arXiv:2104.14490•Physical Review A•Nov 18, 2021•9 citations

Coherent manipulation of a tunable hybrid qubit via microwave control

Si‐Si Gu, Bao‐Chuan Wang, Hai-Ou Li +2 more

Hybrid qubits enable the hybridization of charge and spin degrees of freedom, which provides a way to realize both a relatively long coherence time and rapid qubit manipulation. Here, we use microwave driving to demonstrate the coherent operation of a tunable hybrid qubit, including X-rotation, Z-rotation, and rotation around an arbitrary axis in the X–Y panel of the Bloch sphere. Moreover, the coherence properties of the qubit and its tunability are studied. The measured coherence time of the X-rotation reaches ∼14.3 ns. While for the Z-rotation, the maximum decoherence time is ∼5.8 ns due to the larger sensitivity to noise. By employing the Hahn echo sequence to mitigate the influence of the low-frequency noise, we have improved the qubit coherence time from ∼5.8 ns to ∼15.0 ns. Our results contribute to a further understanding of the hybrid qubit and a step towards achieving high-fidelity qubit gates in the hybrid qubit.

Chinese Physics B•Apr 27, 2023•0 citations

rf-SQUID-Mediated Coherent Tunable Coupling between a Superconducting Phase Qubit and a Lumped-Element Resonator

Michael S. Allman, Fabio Altomare, Jed D. Whittaker +6 more

We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumped-element resonator. The coupling strength is mediated by a flux-biased rf SQUID operated in the nonhysteretic regime. By tuning the applied flux bias to the rf SQUID we change the effective mutual inductance, and thus the coupling energy, between the phase qubit and resonator. We verify the modulation of coupling strength from 0 to 100 MHz by observing modulation in the size of the splitting in the phase qubit's spectroscopy, as well as coherently by observing modulation in the vacuum Rabi oscillation frequency when on resonance. The measured spectroscopic splittings and vacuum Rabi oscillations agree well with theoretical predictions.

arXiv:1001.0816•Physical Review Letters•Apr 29, 2010•89 citations

Coherent control of a superconducting qubit with dynamically tunable qubit-cavity coupling

Anthony J. Hoffman, Srikanth J. Srinivasan, Jay Gambetta +1 more

We demonstrate coherent control and measurement of a superconducting qubit coupled to a superconducting coplanar waveguide resonator with a dynamically tunable qubit-cavity coupling strength. Rabi oscillations are measured for several coupling strengths showing that the qubit transition can be turned off by a factor of more than 1500. We show how the qubit can still be accessed in the off state via fast flux pulses. We perform pulse delay measurements with synchronized fast flux pulses on the device and observe ${T}_{1}$ and ${T}_{2}$ times of 1.6 and 1.9 $\ensuremath{\mu}$s, respectively. This work demonstrates how this qubit can be incorporated into quantum architectures.

arXiv:1108.2705•Physical Review B•Nov 14, 2011•47 citations

Rabi spectroscopy of a qubit-fluctuator system

Jürgen Lisenfeld, Clemens Müller, Jared H. Cole +4 more

Superconducting qubits often show signatures of coherent coupling to microscopic two-level fluctuators (TLFs), which manifest themselves as avoided level crossings in spectroscopic data. In this work we study a phase qubit, in which we induce Rabi oscillations by resonant microwave driving. When the qubit is tuned close to the resonance with an individual TLF and the Rabi driving is strong enough (Rabi frequency of order of the qubit-TLF coupling), interesting four-level dynamics are observed. The experimental data show a clear asymmetry between biasing the qubit above or below the fluctuator's level splitting. Theoretical analysis indicates that this asymmetry is due to an effective coupling of the TLF to the external microwave field induced by the higher qubit levels.

arXiv:0909.3425•Physical Review B•Mar 25, 2010•36 citations
We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.
We infer the high-frequency flux noise spectrum in a superconducting flux qubit by studying the decay of Rabi oscillations under strong driving conditions. The large anharmonicity of the qubit and its strong inductive coupling to a microwave line enabled high-amplitude driving without causing significant additional decoherence. Rabi frequencies up to 1.7 GHz were achieved, approaching the qubit's level splitting of 4.8 GHz, a regime where the rotating-wave approximation breaks down as a model for the driven dynamics. The spectral density of flux noise observed in the wide frequency range decreases with increasing frequency up to 300 MHz, where the spectral density is not very far from the extrapolation of the 1/f1/f1/f spectrum obtained from the free-induction-decay measurements. We discuss a possible origin of the flux noise due to surface electron spins.
We present theoretical transmission spectra of a strongly driven, damped flux qubit coupled to a dissipative resonator in the ultrastrong-coupling regime. Such a qubit-oscillator system, described within a dissipative Rabi model, constitutes the building block of superconducting circuit QED platforms. The addition of a strong drive allows one to characterize the system properties and study novel phenomena, leading to a better understanding and control of the qubit-oscillator system. In this work, the calculated transmission of a weak probe field quantifies the response of the qubit, in frequency domain, under the influence of the quantized resonator and of the strong microwave drive. We find distinctive features of the entangled driven qubit-resonator spectrum, namely resonant features and avoided crossings, modified by the presence of the dissipative environment. The magnitude, positions, and broadening of these features are determined by the interplay among qubit-oscillator detuning, the strength of their coupling, the driving amplitude, and the interaction with the heat bath. This work establishes the theoretical basis for future experiments in the driven ultrastrong-coupling regime.
Hybrid qubits enable the hybridization of charge and spin degrees of freedom, which provides a way to realize both a relatively long coherence time and rapid qubit manipulation. Here, we use microwave driving to demonstrate the coherent operation of a tunable hybrid qubit, including X-rotation, Z-rotation, and rotation around an arbitrary axis in the X–Y panel of the Bloch sphere. Moreover, the coherence properties of the qubit and its tunability are studied. The measured coherence time of the X-rotation reaches ∼14.3 ns. While for the Z-rotation, the maximum decoherence time is ∼5.8 ns due to the larger sensitivity to noise. By employing the Hahn echo sequence to mitigate the influence of the low-frequency noise, we have improved the qubit coherence time from ∼5.8 ns to ∼15.0 ns. Our results contribute to a further understanding of the hybrid qubit and a step towards achieving high-fidelity qubit gates in the hybrid qubit.
We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumped-element resonator. The coupling strength is mediated by a flux-biased rf SQUID operated in the nonhysteretic regime. By tuning the applied flux bias to the rf SQUID we change the effective mutual inductance, and thus the coupling energy, between the phase qubit and resonator. We verify the modulation of coupling strength from 0 to 100 MHz by observing modulation in the size of the splitting in the phase qubit's spectroscopy, as well as coherently by observing modulation in the vacuum Rabi oscillation frequency when on resonance. The measured spectroscopic splittings and vacuum Rabi oscillations agree well with theoretical predictions.
We demonstrate coherent control and measurement of a superconducting qubit coupled to a superconducting coplanar waveguide resonator with a dynamically tunable qubit-cavity coupling strength. Rabi oscillations are measured for several coupling strengths showing that the qubit transition can be turned off by a factor of more than 1500. We show how the qubit can still be accessed in the off state via fast flux pulses. We perform pulse delay measurements with synchronized fast flux pulses on the device and observe T1{T}_{1}T1​ and T2{T}_{2}T2​ times of 1.6 and 1.9 $\ensuremath{\mu}$s, respectively. This work demonstrates how this qubit can be incorporated into quantum architectures.
Superconducting qubits often show signatures of coherent coupling to microscopic two-level fluctuators (TLFs), which manifest themselves as avoided level crossings in spectroscopic data. In this work we study a phase qubit, in which we induce Rabi oscillations by resonant microwave driving. When the qubit is tuned close to the resonance with an individual TLF and the Rabi driving is strong enough (Rabi frequency of order of the qubit-TLF coupling), interesting four-level dynamics are observed. The experimental data show a clear asymmetry between biasing the qubit above or below the fluctuator's level splitting. Theoretical analysis indicates that this asymmetry is due to an effective coupling of the TLF to the external microwave field induced by the higher qubit levels.