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:cond-mat/0108509 · Physical review. B, Condensed matter

Nonlinear backreaction in a quantum mechanical SQUID

Jason F. Ralph, Terrence D. Clark, M. J. Everitt, P. B. Stiffell

Published Oct 3, 2001• 5 citations
arXivHTMLPDF

Abstract

In this paper we discuss the coupling between a quantum mechanical superconducting quantum interference device (SQUID) and an applied static magnetic field. We demonstrate that the backreaction of a SQUID on the applied field can interfere with the ability to bias the SQUID at values of the static (dc) magnetic flux at, or near to, transitions in the quantum mechanical SQUID.

DOI
10.1103/physrevb.64.180504

Related papers

Control of a superconducting qubit in the presence of a nonlinear backreaction

Jason F. Ralph, Terrence D. Clark, M. J. Everitt +3 more

There are a number of systems that are currently being considered as candidates for the construction of qubits, quantum logic gates and quantum computers. Some of the systems, notably atoms in magnetic traps and nuclear magnetic resonance (NMR) systems, have had some success in performing the elementary operations that would be required in large-scale quantum computer. However, these systems are not necessarily seen as viable technologies for quantum computing in the longer term. The recent demonstration of macroscopic coherence in a superconducting ring (consisting of a thick superconducting ring containing one or more Josephson weak link devices) has added significant weight to the idea of using superconducting persistent current devices (SQUIDs) in quantum logic systems. In this paper, we consider one aspect of the quantum mechanical SQUID, the nonlinear effect of SQUID on the classical control parameters, and we discuss how it may influence the construction and design of quantum logic gates based on SQUID devices. In particular, we look at problems associated with fixing the classical magnetic flux bias for a quantum mechanical SQUID at, or near, a quantum mechanical transition or resonance.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Jul 31, 2002•0 citations

Tunable strong nonlinearity of a micromechanical beam embedded in a dc-superconducting quantum interference device

Lior Ella, D. Yuvaraj, Oren Suchoi +2 more

We present a study of the controllable nonlinear dynamics of a micromechanical beam coupled to a dc-SQUID (superconducting quantum interference device). The coupling between these systems places the modes of the beam in a highly nonlinear potential, whose shape can be altered by varying the bias current and applied flux of the SQUID. We detect the position of the beam by placing it in an optical cavity, which sets free the SQUID to be used solely for actuation. This enables us to probe the previously unexplored full parameter space of this device. We measure the frequency response of the beam and find that it displays a Duffing oscillator behavior which is periodic in the applied magnetic flux. To account for this, we develop a model based on the standard theory for SQUID dynamics. In addition, with the aim of understanding if the device can reach nonlinearity at the single phonon level, we use this model to show that the responsivity of the current circulating in the SQUID to the position of the beam can become divergent, with its magnitude limited only by noise. This suggests a direction for the generation of macroscopically distinguishable superposition states of the beam.

Journal of Applied Physics•Jan 6, 2015•4 citations

Tuning an rf-SQUID flux qubit system's potential with magnetic flux bias

Tao Hua, Weiwei Xu, Jianxin Shi +4 more

At an extremely low temperature of 20 mK, we measured the loop current in a tunable rf superconducting quantum interference device (SQUID) with a dc-SQUID. By adjusting the magnetic flux applied to the rf-SQUID loop ( Φ f ) and the small dc-SQUID ( Φ f cjj ), respectively, the potential shape of the system can be fully controlled in situ . Variation in the transition step and overlap size in the switching current with a barrier flux bias are analyzed, from which we can obtain some relevant device parameters and build a model to explain the experimental phenomenon.

Chinese Physics B•Sep 1, 2012•4 citations

Tuning an rf-SQUID flux qubit system＇s potential with magnetic flux bias

花涛, 许伟伟, 史建新 +4 more

At an extremely low temperature of 20 mK, we measured the loop current in a tunable rf superconducting quantum interference device (SQUID) with a dc-SQUID. By adjusting the magnetic flux applied to the rf-SQUID loop (Φ f ) and the small dc-SQUID (Φ cjj f ), respectively, the potential shape of the system can be fully controlled in situ. Variation in the transition step and overlap size in the switching current with a barrier flux bias are analyzed, from which we can obtain some relevant device parameters and build a model to explain the experimental phenomenon.

中国物理B：英文版•Jan 1, 2012•0 citations

Hard Magnetic Dots for Flux Bias of DC SQUIDs

Dušan S. Golubović, V. V. Moshchalkov

In this paper, we demonstrate that perpendicularly magnetized sub- and micrometer-sized magnetic dots, with a high coercivity and nearly complete remanence, can be used to provide the flux bias for dc superconducting quantum interference devices (SQUIDs). The radius of a submicrometer Co-Pd magnetic dot has been optimized with respect to the surrounding superconducting circuitry to generate the phase shift of approximately pi/2 in it. In this way, it is possible to bias a dc SQUID to the steepest part of its voltage-flux characteristic without using an additional coil and current source. Furthermore, it has been shown that the flux bias can also be achieved using a micrometer-sized Co-Pd dot, upon saturation, by placing a dc SQUID on top of the dot. Given that the underlying principles of flux biasing do not require any particular superconducting pairing scheme (s- or d-wave), these hybrid superconductor/ferromagnet structures can be used as to design a dc SQUID with a complete flux self-biasing

IEEE Transactions on Applied Superconductivity•Sep 1, 2006•0 citations

Solid-State Qubits with Current-Controlled Coupling

T. Hime, P. A. Reichardt, B. L. T. Plourde +4 more

The ability to switch the coupling between quantum bits (qubits) on and off is essential for implementing many quantum-computing algorithms. We demonstrated such control with two flux qubits coupled together through their mutual inductances and through the dc superconducting quantum interference device (SQUID) that reads out their magnetic flux states. A bias current applied to the SQUID in the zero-voltage state induced a change in the dynamic inductance, reducing the coupling energy controllably to zero and reversing its sign.

Science•Nov 30, 2006•228 citations
In this paper we discuss the coupling between a quantum mechanical superconducting quantum interference device (SQUID) and an applied static magnetic field. We demonstrate that the backreaction of a SQUID on the applied field can interfere with the ability to bias the SQUID at values of the static (dc) magnetic flux at, or near to, transitions in the quantum mechanical SQUID.
There are a number of systems that are currently being considered as candidates for the construction of qubits, quantum logic gates and quantum computers. Some of the systems, notably atoms in magnetic traps and nuclear magnetic resonance (NMR) systems, have had some success in performing the elementary operations that would be required in large-scale quantum computer. However, these systems are not necessarily seen as viable technologies for quantum computing in the longer term. The recent demonstration of macroscopic coherence in a superconducting ring (consisting of a thick superconducting ring containing one or more Josephson weak link devices) has added significant weight to the idea of using superconducting persistent current devices (SQUIDs) in quantum logic systems. In this paper, we consider one aspect of the quantum mechanical SQUID, the nonlinear effect of SQUID on the classical control parameters, and we discuss how it may influence the construction and design of quantum logic gates based on SQUID devices. In particular, we look at problems associated with fixing the classical magnetic flux bias for a quantum mechanical SQUID at, or near, a quantum mechanical transition or resonance.
We present a study of the controllable nonlinear dynamics of a micromechanical beam coupled to a dc-SQUID (superconducting quantum interference device). The coupling between these systems places the modes of the beam in a highly nonlinear potential, whose shape can be altered by varying the bias current and applied flux of the SQUID. We detect the position of the beam by placing it in an optical cavity, which sets free the SQUID to be used solely for actuation. This enables us to probe the previously unexplored full parameter space of this device. We measure the frequency response of the beam and find that it displays a Duffing oscillator behavior which is periodic in the applied magnetic flux. To account for this, we develop a model based on the standard theory for SQUID dynamics. In addition, with the aim of understanding if the device can reach nonlinearity at the single phonon level, we use this model to show that the responsivity of the current circulating in the SQUID to the position of the beam can become divergent, with its magnitude limited only by noise. This suggests a direction for the generation of macroscopically distinguishable superposition states of the beam.
At an extremely low temperature of 20 mK, we measured the loop current in a tunable rf superconducting quantum interference device (SQUID) with a dc-SQUID. By adjusting the magnetic flux applied to the rf-SQUID loop ( Φ f ) and the small dc-SQUID ( Φ f cjj ), respectively, the potential shape of the system can be fully controlled in situ . Variation in the transition step and overlap size in the switching current with a barrier flux bias are analyzed, from which we can obtain some relevant device parameters and build a model to explain the experimental phenomenon.
At an extremely low temperature of 20 mK, we measured the loop current in a tunable rf superconducting quantum interference device (SQUID) with a dc-SQUID. By adjusting the magnetic flux applied to the rf-SQUID loop (Φ f ) and the small dc-SQUID (Φ cjj f ), respectively, the potential shape of the system can be fully controlled in situ. Variation in the transition step and overlap size in the switching current with a barrier flux bias are analyzed, from which we can obtain some relevant device parameters and build a model to explain the experimental phenomenon.
In this paper, we demonstrate that perpendicularly magnetized sub- and micrometer-sized magnetic dots, with a high coercivity and nearly complete remanence, can be used to provide the flux bias for dc superconducting quantum interference devices (SQUIDs). The radius of a submicrometer Co-Pd magnetic dot has been optimized with respect to the surrounding superconducting circuitry to generate the phase shift of approximately pi/2 in it. In this way, it is possible to bias a dc SQUID to the steepest part of its voltage-flux characteristic without using an additional coil and current source. Furthermore, it has been shown that the flux bias can also be achieved using a micrometer-sized Co-Pd dot, upon saturation, by placing a dc SQUID on top of the dot. Given that the underlying principles of flux biasing do not require any particular superconducting pairing scheme (s- or d-wave), these hybrid superconductor/ferromagnet structures can be used as to design a dc SQUID with a complete flux self-biasing
The ability to switch the coupling between quantum bits (qubits) on and off is essential for implementing many quantum-computing algorithms. We demonstrated such control with two flux qubits coupled together through their mutual inductances and through the dc superconducting quantum interference device (SQUID) that reads out their magnetic flux states. A bias current applied to the SQUID in the zero-voltage state induced a change in the dynamic inductance, reducing the coupling energy controllably to zero and reversing its sign.