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A dc SQUID coupled to a high Q electrical resonator

P. Falferi, R. Mezzena, MASSIMO CERDONIO +3 more

Czechoslovak Journal of PhysicsMay 1, 19961 citation

Coupling nanoscale spin ensembles to a SQUID embedded in superconducting circuits

Christopher Eichler, J. R. Petta

Bulletin of the American Physical SocietyMar 15, 20160 citations

Quantum dynamics of a dc-SQUID coupled to an asymmetric Cooper pair transistor

Aurélien Fay, Wiebke Guichard, O. Buisson +1 more

We present a theoretical analysis of the quantum dynamics of a superconducting circuit based on a highly asymmetric Cooper pair transistor (ACPT) in parallel to a dc-SQUID. Starting from the full Hamiltonian we show that the circuit can be modeled as a charge qubit (ACPT) coupled to an anharmonic oscillator (dc-SQUID). Depending on the anharmonicity of the SQUID, the Hamiltonian can be reduced either to one that describes two coupled qubits or to the Jaynes-Cummings Hamiltonian. Here the dc-SQUID can be viewed as a tunable micron-size resonator. The coupling term, which is a combination of a capacitive and a Josephson coupling between the two qubits, can be tuned from the very strong- to the zero-coupling regimes. It describes very precisely the tunable coupling strength measured in this circuit and explains the 'quantronium' as well as the adiabatic quantum transfer read-out.We present a theoretical analysis of the quantum dynamics of a superconducting circuit based on a highly asymmetric Cooper pair transistor (ACPT) in parallel to a dc-SQUID. Starting from the full Hamiltonian we show that the circuit can be modeled as a charge qubit (ACPT) coupled to an anharmonic oscillator (dc-SQUID). Depending on the anharmonicity of the SQUID, the Hamiltonian can be reduced either to one that describes two coupled qubits or to the Jaynes-Cummings Hamiltonian. Here the dc-SQUID can be viewed as a tunable micron-size resonator. The coupling term, which is a combination of a capacitive and a Josephson coupling between the two qubits, can be tuned from the very strong- to the zero-coupling regimes. It describes very precisely the tunable coupling strength measured in this circuit and explains the 'quantronium' as well as the adiabatic quantum transfer read-out.

arXiv:1011.6148Nov 29, 20100 citations

Optimization of dc SQUID linear amplifiers and the quantum noise limit

Claudia D. Tesche

A model for inductively coupled linear amplifier and magnetometer circuits employing superconducting quantum interference devices (dc SQUID’s), which is accurate to all values in the coupling strength, is described. The model explicitly includes the interaction between the input circuit and the dc SQUID. The optimization of the untuned linear amplifier is discussed in detail. The uncertainty principle constraint on the noise temperature of a linear amplifier is shown to place a constraint on the minimum achievable values of the noise figures of an isolated dc SQUID in the quantum noise limit.A model for inductively coupled linear amplifier and magnetometer circuits employing superconducting quantum interference devices (dc SQUID’s), which is accurate to all values in the coupling strength, is described. The model explicitly includes the interaction between the input circuit and the dc SQUID. The optimization of the untuned linear amplifier is discussed in detail. The uncertainty principle constraint on the noise temperature of a linear amplifier is shown to place a constraint on the minimum achievable values of the noise figures of an isolated dc SQUID in the quantum noise limit.

Applied Physics LettersSep 1, 198235 citations

The interactions of two mutually inductive-coupled dc SQUIDs

C.C. Chi, Lia Krusin-Elbaum, Chang C. Tsuei

Physica B+CAug 1, 19813 citations

Superconducting non-linear resonator for non-destructive readout of a flux qubit

K. Inomata, 道生渡部, Tsuyoshi Yamamoto +3 more

We have investigated microwave response of a λ/4 superconducting coplanar waveguide resonator which is terminated by a DC-SQUID coupled with a flux qubit. The circuit is designed for non-destructive single-shot readout of a flux qubit based on dispersive interaction between the qubit and the resonator and switching between bistable states of the driven nonlinear resonator. A high-frequency (∼ 10 GHz) resonator is exploited for suppressing photon-number fluctuations which cause qubit dephasing even when the readout circuit is not activated. We observed bifurcation of the resonator in the nonlinear driving regime. In the linear regime, the degeneracy point of the qubit was detected as a shift of the resonant frequency.We have investigated microwave response of a λ/4 superconducting coplanar waveguide resonator which is terminated by a DC-SQUID coupled with a flux qubit. The circuit is designed for non-destructive single-shot readout of a flux qubit based on dispersive interaction between the qubit and the resonator and switching between bistable states of the driven nonlinear resonator. A high-frequency (∼ 10 GHz) resonator is exploited for suppressing photon-number fluctuations which cause qubit dephasing even when the readout circuit is not activated. We observed bifurcation of the resonator in the nonlinear driving regime. In the linear regime, the degeneracy point of the qubit was detected as a shift of the resonant frequency.

Journal of Physics Conference SeriesMar 1, 20094 citations

Non-resonant interactions between superconducting circuits coupled through a dc-SQUID

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