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:1309.1733 · Physical Review A

Superconducting qubit as a probe of squeezing in a nonlinear resonator

Maxime Boissonneault, Andrew C. Doherty, Florian R. Ong, Patrice Bertet, D. Vion, D. Esteve, Alexandre Blais

Published Feb 18, 2014• 10 citations
arXivHTMLPDF

Abstract

In addition to their central role in quantum information processing, qubits have proven to be useful tools in a range of other applications such as enhanced quantum sensing and as spectrometers of quantum noise. Here we show that a superconducting qubit strongly coupled to a nonlinear resonator can act as a probe of quantum fluctuations of the intraresonator field. Building on previous work [M. Boissoneault et al., Phys. Rev. A 85, 022305 (2012)], we derive an effective master equation for the qubit which takes into account squeezing of the resonator field. We show how sidebands in the qubit excitation spectrum that are predicted by this model can reveal information about the squeezing factor $r$. The main results of this paper have already been successfully compared to experimental data [F. R. Ong et al., Phys. Rev. Lett. 110, 047001 (2013)], and we present here the details of the derivations.

DOI
10.1103/physreva.89.022324

Related papers

Quantum Heating of a Nonlinear Resonator Probed by a Superconducting Qubit

Florian R. Ong, Maxime Boissonneault, F. Mallet +5 more

We measure the quantum fluctuations of a pumped nonlinear resonator using a superconducting artificial atom as an in situ probe. The qubit excitation spectrum gives access to the frequency and amount of excitation of the intracavity field fluctuations, from which we infer its effective temperature. These quantities are found to be in agreement with theoretical predictions; in particular, we experimentally observe the phenomenon of quantum heating.

arXiv:1210.3472•Physical Review Letters•Jan 22, 2013•40 citations

Quantum squeezing in a nonlinear mechanical oscillator

Stefano Marti, Uwe von Lüpke, Om Joshi +5 more

Abstract Mechanical degrees of freedom are natural candidates for continuous-variable quantum information processing and bosonic quantum simulations. However, these applications require the engineering of squeezing and nonlinearities in the quantum regime. Here we demonstrate squeezing below the zero-point fluctuations of a gigahertz-frequency mechanical resonator coupled to a superconducting qubit. This is achieved by parametrically driving the qubit, which results in an effective two-phonon drive. In addition, we show that the resonator mode inherits a nonlinearity from the off-resonant coupling with the qubit, which can be tuned by controlling the detuning. We, thus, realize a mechanical squeezed Kerr oscillator, in which we demonstrate the preparation of non-Gaussian quantum states of motion with Wigner function negativities and high quantum Fisher information. This shows that our results can also have applications in quantum metrology and sensing.

Nature Physics•Jun 21, 2024•58 citations

Microwave Bistability in Circuit QED

Andrew C. Doherty

Recent experiments have realized a familiar model of quantum optics, dispersive optical bistability, in the context of microwave coplanar resonators with internal Josephson junctions that are used to achieve large effective Kerr nonlinearities with very low dissipation. A Josephson junction qubit constitutes an effective atom that may be coupled to such a nonlinear resonator to provide a very useful probe that is sensitive to the quantum noise in the nonlinear cavity. In particular, I will explain how sidebands on the qubit excitation spectrum are sensitive to the effective temperature, oscillation frequency and damping rate of the intracavity field fluctuations.

•Jan 1, 2011•0 citations

Microwave bistability in circuit QED

Andrew C. Doherty

Recent experiments have realized a familiar model of quantum optics, dispersive optical bistability, in the context of microwave coplanar resonators with internal Josephson junctions that are used to achieve large effective Kerr nonlinearities with very low dissipation. A Josephson junction qubit constitutes an effective atom that may be coupled to such a nonlinear resonator to provide a very useful probe that is sensitive to the quantum noise in the nonlinear cavity. In particular, I will explain how sidebands on the qubit excitation spectrum are sensitive to the effective temperature, oscillation frequency and damping rate of the intracavity field fluctuations.

•Aug 1, 2011•0 citations

Quantum squeezing in a nonlinear mechanical oscillator

Stefano Marti, Uwe von Lüpke, Om Joshi +5 more

Mechanical degrees of freedom are natural candidates for continuous-variable quantum information processing and bosonic quantum simulations. These applications, however, require the engineering of squeezing and nonlinearities in the quantum regime. Here we demonstrate ground state squeezing of a gigahertz-frequency mechanical resonator coupled to a superconducting qubit. This is achieved by parametrically driving the qubit, which results in an effective two-phonon drive. In addition, we show that the resonator mode inherits a nonlinearity from the off-resonant coupling with the qubit, which can be tuned by controlling the detuning. We thus realize a mechanical squeezed Kerr oscillator, where we demonstrate the preparation of non-Gaussian quantum states of motion with Wigner function negativities and high quantum Fisher information. This shows that our results also have applications in quantum metrology and sensing.

arXiv:2312.16169•Dec 26, 2023•2 citations

Superconducting Circuits for Quantum Metrology with Nonclassical Light

Andrew Eddins

The laws of quantum mechanics imply the existence of an intrinsic uncertainty, or noise, in the electromagnetic field. These noise fluctuations are central to many processes in atomic physics and quantum optics, including spontaneous emission of radiation by an atomic system, backaction on an atomic system during non-demolition measurement by probe light, and intrinsic bounds on the noise performance of an ideal amplifier. While quantum noise cannot be eliminated, the noise of one observable quantity may be reduced provided that of the conjugate observable is increased in accord with the relevant Heisenberg uncertainty relation; this process is known as squeezing.Recently, superconducting circuits have emerged as a powerful platform for studying the interaction of squeezed light and matter, leveraging the low-dimensionality of the circuit environment to efficiently couple atomic systems to squeezed radiation. Beyond enabling the verification of canonical predictions of quantum optics, these experiments explore the potential utility of squeezing for the state readout of quantum bits, or qubits, used for quantum information processing.In this thesis, we present three experiments probing the interaction of a superconducting qubit with squeezed radiation. First, we observe how the fluorescence spectra emitted by a two-level atomic system are modified by squeezing of a resonant drive. The subnatural linewidths of the resulting spectra provide the first successful verification in any system of predictions from nearly three decades prior, and provide a tool for characterization of microwave squeezed states. Second, we combine injected squeezed noise with a stroboscopic measurement scheme to demonstrate the first improvement of the signal-to-noise ratio of qubit state readout due to input squeezing. This study includes a characterization of the effect of squeezing on measurement backaction, exhibiting the first use of squeezing to slow measurement-induced dephasing. Finally, we develop a circuit incorporating the qubit inside of a squeezed-microwave source and extensively study the measurement physics of this hybrid system. This device enables the transfer of quantum information from the qubit at $\\sim$30 milliKelvin to a room temperature detector with a marked increase in steady-state efficiency.

•Jan 1, 2017•2 citations
In addition to their central role in quantum information processing, qubits have proven to be useful tools in a range of other applications such as enhanced quantum sensing and as spectrometers of quantum noise. Here we show that a superconducting qubit strongly coupled to a nonlinear resonator can act as a probe of quantum fluctuations of the intraresonator field. Building on previous work [M. Boissoneault et al., Phys. Rev. A 85, 022305 (2012)], we derive an effective master equation for the qubit which takes into account squeezing of the resonator field. We show how sidebands in the qubit excitation spectrum that are predicted by this model can reveal information about the squeezing factor rrr. The main results of this paper have already been successfully compared to experimental data [F. R. Ong et al., Phys. Rev. Lett. 110, 047001 (2013)], and we present here the details of the derivations.
Abstract Mechanical degrees of freedom are natural candidates for continuous-variable quantum information processing and bosonic quantum simulations. However, these applications require the engineering of squeezing and nonlinearities in the quantum regime. Here we demonstrate squeezing below the zero-point fluctuations of a gigahertz-frequency mechanical resonator coupled to a superconducting qubit. This is achieved by parametrically driving the qubit, which results in an effective two-phonon drive. In addition, we show that the resonator mode inherits a nonlinearity from the off-resonant coupling with the qubit, which can be tuned by controlling the detuning. We, thus, realize a mechanical squeezed Kerr oscillator, in which we demonstrate the preparation of non-Gaussian quantum states of motion with Wigner function negativities and high quantum Fisher information. This shows that our results can also have applications in quantum metrology and sensing.
Recent experiments have realized a familiar model of quantum optics, dispersive optical bistability, in the context of microwave coplanar resonators with internal Josephson junctions that are used to achieve large effective Kerr nonlinearities with very low dissipation. A Josephson junction qubit constitutes an effective atom that may be coupled to such a nonlinear resonator to provide a very useful probe that is sensitive to the quantum noise in the nonlinear cavity. In particular, I will explain how sidebands on the qubit excitation spectrum are sensitive to the effective temperature, oscillation frequency and damping rate of the intracavity field fluctuations.
Recent experiments have realized a familiar model of quantum optics, dispersive optical bistability, in the context of microwave coplanar resonators with internal Josephson junctions that are used to achieve large effective Kerr nonlinearities with very low dissipation. A Josephson junction qubit constitutes an effective atom that may be coupled to such a nonlinear resonator to provide a very useful probe that is sensitive to the quantum noise in the nonlinear cavity. In particular, I will explain how sidebands on the qubit excitation spectrum are sensitive to the effective temperature, oscillation frequency and damping rate of the intracavity field fluctuations.
Mechanical degrees of freedom are natural candidates for continuous-variable quantum information processing and bosonic quantum simulations. These applications, however, require the engineering of squeezing and nonlinearities in the quantum regime. Here we demonstrate ground state squeezing of a gigahertz-frequency mechanical resonator coupled to a superconducting qubit. This is achieved by parametrically driving the qubit, which results in an effective two-phonon drive. In addition, we show that the resonator mode inherits a nonlinearity from the off-resonant coupling with the qubit, which can be tuned by controlling the detuning. We thus realize a mechanical squeezed Kerr oscillator, where we demonstrate the preparation of non-Gaussian quantum states of motion with Wigner function negativities and high quantum Fisher information. This shows that our results also have applications in quantum metrology and sensing.
The laws of quantum mechanics imply the existence of an intrinsic uncertainty, or noise, in the electromagnetic field. These noise fluctuations are central to many processes in atomic physics and quantum optics, including spontaneous emission of radiation by an atomic system, backaction on an atomic system during non-demolition measurement by probe light, and intrinsic bounds on the noise performance of an ideal amplifier. While quantum noise cannot be eliminated, the noise of one observable quantity may be reduced provided that of the conjugate observable is increased in accord with the relevant Heisenberg uncertainty relation; this process is known as squeezing.Recently, superconducting circuits have emerged as a powerful platform for studying the interaction of squeezed light and matter, leveraging the low-dimensionality of the circuit environment to efficiently couple atomic systems to squeezed radiation. Beyond enabling the verification of canonical predictions of quantum optics, these experiments explore the potential utility of squeezing for the state readout of quantum bits, or qubits, used for quantum information processing.In this thesis, we present three experiments probing the interaction of a superconducting qubit with squeezed radiation. First, we observe how the fluorescence spectra emitted by a two-level atomic system are modified by squeezing of a resonant drive. The subnatural linewidths of the resulting spectra provide the first successful verification in any system of predictions from nearly three decades prior, and provide a tool for characterization of microwave squeezed states. Second, we combine injected squeezed noise with a stroboscopic measurement scheme to demonstrate the first improvement of the signal-to-noise ratio of qubit state readout due to input squeezing. This study includes a characterization of the effect of squeezing on measurement backaction, exhibiting the first use of squeezing to slow measurement-induced dephasing. Finally, we develop a circuit incorporating the qubit inside of a squeezed-microwave source and extensively study the measurement physics of this hybrid system. This device enables the transfer of quantum information from the qubit at $\\sim$30 milliKelvin to a room temperature detector with a marked increase in steady-state efficiency.