Dispersive magnetometry with a quantum limited SQUID parametric amplifier

Hatridge, Michael; Vijay, R.; Slichter, Daniel; Clarke, John; Siddiqi, Irfan

doi:10.1103/physrevb.83.134501

Cited by 261 publications

(280 citation statements)

References 33 publications

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“…Thus, by simply using two current pumps instead of one, the deviation from the expected results for a DPA are reduced by approximately two orders of magnitude. To put in context the range of Kerr nonlinearity considered, the vertical lines indicate approximate experimental parameters of three recent experiments with JPAs [7,29,37]. We note that, in practice, the smaller nonlinearity (dashed gray line) is obtained using junction arrays.…”

Section: A Deviation From Standard Dpa Resultsmentioning

confidence: 99%

Effect of Higher-Order Nonlinearities on Amplification and Squeezing in Josephson Parametric Amplifiers

et al. 2017

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Single-mode Josephson junction-based parametric amplifiers are often modeled as perfect amplifiers and squeezers. We show that, in practice, the gain, quantum efficiency, and output field squeezing of these devices are limited by usually neglected higher-order corrections to the idealized model. To arrive at this result, we derive the leading corrections to the lumped-element Josephson parametric amplifier of three common pumping schemes: monochromatic current pump, bichromatic current pump, and monochromatic flux pump. We show that the leading correction for the last two schemes is a single Kerr-type quartic term, while the first scheme contains additional cubic terms. In all cases, we find that the corrections are detrimental to squeezing. In addition, we show that the Kerr correction leads to a strongly phase-dependent reduction of the quantum efficiency of a phase-sensitive measurement. Finally, we quantify the departure from ideal Gaussian character of the filtered output field from numerical calculation of third and fourth order cumulants. Our results show that, while a Gaussian output field is expected for an ideal Josephson parametric amplifier, higher-order corrections lead to non-Gaussian effects which increase with both gain and nonlinearity strength. This theoretical study is complemented by experimental characterization of the output field of a flux-driven Josephson parametric amplifier. In addition to a measurement of the squeezing level of the filtered output field, the Husimi Q-function of the output field is imaged by the use of a deconvolution technique and compared to numerical results. This work establishes nonlinear corrections to the standard degenerate parametric amplifier model as an important contribution to Josephson parametric amplifier's squeezing and noise performance.

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Section: A Deviation From Standard Dpa Resultsmentioning

confidence: 99%

Effect of Higher-Order Nonlinearities on Amplification and Squeezing in Josephson Parametric Amplifiers

et al. 2017

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“…In general, nonlinear cavity response is commonly employed for frequency mixing, which in turn can be used for signal amplification [37,38,[41][42][43] and noise squeezing [39,41]. An amplifier based on flux qubits has been recently demonstrated in Ref.…”

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confidence: 99%

Superharmonic resonances in a strongly coupled cavity-atom system

Buks¹,

Deng²,

Orgazzi³

et al. 2016

Phys. Rev. A

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We study a system consisting of a superconducting flux qubit strongly coupled to a microwave cavity. The fundamental cavity mode is externally driven and the response is investigated in the weak nonlinear regime. We find that near the crossing point, at which the resonance frequencies of the cavity mode and qubit coincide, the sign of the Kerr coefficient changes, and consequently the type of nonlinear response changes from softening to hardening. Furthermore, the cavity response exhibits superharmonic resonances when the ratio between the qubit frequency and the cavity fundamental mode frequency is tuned close to an integer value. The nonlinear response is characterized by the method of intermodulation and both signal and idler gains are measured. Cavity quantum electrodynamics (CQED) [1] is the study of the interaction between photons confined in a cavity and atoms (natural or artificial). The interaction is commonly described by the Rabi or Jaynes-Cummings Hamiltonians [2], and it has been the subject of numerous theoretical and experimental investigations. An on-chip CQED system can be realized by integrating a Josephson qubit [3][4][5] (playing the role of an artificial atom) with a superconducting microwave resonator (cavity) [6][7][8]. Superconducting CQED systems have generated a fast growing interest due to the possibility to reach the strong [7] and ultra-strong [9, 10] coupling regimes, and due to potential applications in quantum information processing [4,[11][12][13].In this study we investigate the driven dynamics of a strongly interacting system composed of a superconducting flux qubit [15,16] and a coplanar waveguide (CPW) microwave cavity [9,14,[17][18][19][20][21]. The nonlinear cavity response [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] is measured as a function of the magnetic flux that is applied to the qubit. At weak driving and when the ratio between the qubit frequency and the cavity fundamental mode frequency is tuned close to the value ω a /ω c = 1 the common Jaynes-Cummings resonance, which henceforth is referred to as the primary resonance, is observed. With stronger driving, however, and when the ratio ω a /ω c is tuned close to integer values larger than unity, superharmonic resonances appear in the measured response. Intermodulation (IMD) measurements are employed to characterize the nonlinear response [37][38][39]. The results are compared with the predictions of a theoretical model, which is based on linearization of the equations of motion that govern the dynamics of the CQED system under study.

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“…Noise impairs the performance of a variety of devices based on superconducting circuits, e.g., photon detectors used in astrophysics [1], bolometers used in the search for dark matter [2], nanomechanical motion sensors [3], and quantum-limited parametric amplifiers [4]. Of particular interest are superconducting quantum interference devices (SQUIDs) [5] where low frequency 1=f magnetic flux noise [6] is one of the dominant sources of noise in superconducting qubits [7][8][9][10].…”

mentioning

confidence: 99%