Observation of Quantum Jumps in a Superconducting Artificial Atom

Vijay, R.; Slichter, Daniel; Siddiqi, Irfan

doi:10.1103/physrevlett.106.110502

Cited by 371 publications

(383 citation statements)

References 31 publications

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“…This design is of particular interest as it has been widely adopted for superconducting qubit readout [8,13,17]. The device consists of a capacitance (3.2 pF) shunted by a SQUID (L J (Φ = 0) = 45 pH).…”

Section: Appendix B: Details Of the Displacement Transformationsmentioning

confidence: 99%

“…Following the path of Yurke's et al work in the late 1980s [1][2][3], several designs of Josephson junction-based parametric amplifiers (JPAs) have been introduced [4][5][6][7][8][9][10][11]. In addition to high-fidelity superconducting qubit readout leading to the observation of quantum jumps [12,13], this new generation of near quantumlimited amplifiers have opened up new experimental possibilities such as the creation and tomography of squeezed microwave light [14][15][16], and detailed weak measurement experiments [17][18][19]. JPAs are now ubiquitous in current superconducting circuit experiments, and applications in other research communities are growing [20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

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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: Appendix B: Details Of the Displacement Transformationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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“…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.…”

mentioning

confidence: 99%

“…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.…”

mentioning

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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“…quantum jumps. [14] Also, as with superconducting quantum interference devices (SQUIDs), the combination of a limited dynamic range and a limited bandwidth results in a low Shannon information capacity and limits the utility of Josephson paramps for multiplexed readout of detector arrays. [15] Instead of using a resonator, the optical or electrical path may be unfolded into a long nonlinear transmission line or waveguide.…”

mentioning

confidence: 99%

A wideband, low-noise superconducting amplifier with high dynamic range

et al. 2012

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Amplifiers are ubiquitous in electronics and play a fundamental role in a wide range of scientific measurements. From a user's perspective, an ideal amplifier has very low noise, operates over a broad frequency range, and has a high dynamic range -it is capable of handling strong signals with little distortion.Unfortunately, it is difficult to obtain all of these characteristics simultaneously.For example, modern transistor amplifiers offer multi-octave bandwidths and excellent dynamic range. However, their noise remains far above the fundamental limit set by the uncertainty principle of quantum mechanics.[1] Parametric amplifiers, which predate transistor amplifiers and are widely used in optics, exploit a nonlinear response to transfer power from a strong pump tone to a weak signal.If the nonlinearity is purely reactive, i.e. nondissipative, in theory the amplifier noise can reach the quantum-mechanical limit.[2] Indeed, microwave frequency superconducting Josephson parametric amplifiers [3, 4] do approach the quantum limit, but generally are narrow band and have very limited dynamic range. In this paper, we describe a superconducting parametric amplifier that overcomes these limitations. The amplifier is very simple, consisting only of a patterned metal film on a dielectric substrate, and relies on the nonlinear kinetic inductance of a superconducting transmission line. We measure gain extending over 2 GHz on either side of an 11.56 GHz pump tone, and we place an upper limit 1 arXiv:1201.2392v1 [cond-mat.supr-con] 11 Jan 2012 on the added noise of the amplifier of 3.4 photons at 9.4 GHz. Furthermore, the dynamic range is very large, comparable to microwave transistor amplifiers, and the concept can be applied throughout the microwave, millimeter-wave and submillimeter-wave bands.Over the past decade, the combination of high-performance superconducting microresonators and low-noise, microwave frequency cryogenic transistor amplifier readouts has proven to be particularly powerful for a wide range of applications including photon detection and quantum information experiments. [5][6][7] These developments have generated strong renewed interest in superconducting amplifiers that achieve even lower readout noise. [8][9][10][11][12].Most of these devices are parametric amplifiers that make use of the nonlinear inductance of the Josephson junction, which is almost ideally reactive with little dissipation below the critical current I c . As a result, Josephson paramps can be exquisitely sensitive, approaching the standard quantum limit of half a photon ω/2 of added noise power per unit bandwidth in the standard case when both quadratures of a signal at frequency ω are amplified equally.Here is Planck's constant divided by 2π. Even less noise is possible in situations when only one quadrature is amplified. [1]. In comparison, the added noise of cryogenic transistor amplifiers is typically 10-20 times the quantum limit.[13] However, the dynamic range of Josephson paramps is regulated by the Josephson energy E J = I c ...

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Observation of Quantum Jumps in a Superconducting Artificial Atom

Cited by 371 publications

References 31 publications

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

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

Superharmonic resonances in a strongly coupled cavity-atom system

A wideband, low-noise superconducting amplifier with high dynamic range

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