Parametric amplification by unbiased Josephson junctions

Feldman, M.J.; Parrish, P. T.; Chiao, Raymond Y.

doi:10.1063/1.322157

Cited by 97 publications

(27 citation statements)

References 12 publications

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“…(2) as the equation for a parametrically driven harmonic oscillator. For appropriate bias conditions, the system can amplify [25][26][27] any additional weak rf signal with frequency ω rf /2π near ω d /2π. In this doubly degenerate mode of parametric amplification 27 , a single sideband signal at frequency ω rf /2π is amplified with a voltage gain √ G, and an idler signal is also produced at frequency ω i /2π = (2ω d − ω rf )/2π with gain √ G − 1 and phase factor e iφ [ Fig.…”

Section: Theorymentioning

confidence: 99%

Dispersive magnetometry with a quantum limited SQUID parametric amplifier

et al. 2011

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There is currently fundamental and technological interest in measuring and manipulating nanoscale magnets, particularly in the quantum coherent regime. To observe the dynamics of such systems one requires a magnetometer with not only exceptional sensitivity but also high gain, wide bandwidth and low backaction. We demonstrate a dispersive magnetometer consisting of a two-junction SQUID in parallel with an integrated, lumped-element capacitor. Input flux signals are encoded as a phase modulation of the microwave drive tone applied to the magnetometer, resulting in a single quadrature voltage signal. For strong drive power, the nonlinearity of the resonator results in quantum limited, phase sensitive parametric amplification of this signal, which improves flux sensitvity at the expense of bandwidth. Depending on the drive parameters, the device performance ranges from an effective flux noise of 0.29 µΦ0Hz

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Section: Theorymentioning

confidence: 99%

Dispersive magnetometry with a quantum limited SQUID parametric amplifier

et al. 2011

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“…A promising approach is to build a TWPA based on the non-linear inductance of the Josephson junction (JJ) [27][28][29][30][31]. This junction TWPA (JTWPA) circuit, shown in Fig.…”

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confidence: 99%

Traveling wave parametric amplifier with Josephson junctions using minimal resonator phase matching

White

Mutus

Hoi

et al. 2015

Applied Physics Letters

158

174

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Josephson parametric amplifiers have become a critical tool in superconducting device physics due to their high gain and quantum-limited noise. Traveling wave parametric amplifiers (TWPAs) promise similar noise performance while allowing for significant increases in both bandwidth and dynamic range. We present a TWPA device based on an LC-ladder transmission line of Josephson junctions and parallel plate capacitors using low-loss amorphous silicon dielectric. Crucially, we have inserted λ/4 resonators at regular intervals along the transmission line in order to maintain the phase matching condition between pump, signal, and idler and increase gain. We achieve an average gain of 12 dB across a 4 GHz span, along with an average saturation power of -92 dBm with noise approaching the quantum limit.The Josephson parametric amplifier [1][2][3][4][5][6][7] (JPA) is a critical tool for high fidelity state measurement in superconducting qubits [8][9][10] as it allows parametric amplification with near quantum-limited noise [11]. Despite its success, the JPA has typically been used only for single frequency measurements due to lower bandwidth and saturation power. A promising approach to scaling superconducting qubit experiments is frequency multiplexing [12][13][14], which requires additional bandwidth and dynamic range for each measurement tone. Simultaneous amplification of up to five multiplexed tones has been achieved with a JPA [15-17] but was only possible with the Impedance-transformed parametric amplifier [18] (IMPA). This highly engineered JPA provides much larger bandwidth and saturation power but pushes the resonant design to its low Q limit.To extend this frequency multiplexed approach for future experiments, we have adopted the distributed design of the traveling wave parametric amplifier (TWPA) [19]. Fiber-optic TWPAs have already demonstrated high gain, dynamic range, and bandwidth while reaching the quantum-limit of added noise [20,21]. In this letter we present a microwave frequency TWPA with 4 GHz of bandwidth and an order of magnitude more saturation power than the best JPA. This device is compatible with scaling to much larger qubit systems through multiplexed measurement, and may find applications outside quantum information such as astrophysics detectors [12,22] At microwave frequencies the TWPA can be thought of as a transmission line where the propagation velocity is controlled by varying the individual circuit parameters of inductance or capacitance per unit length [24,25]. This is typically achieved by constructing a signal line with a current dependent (nonlinear) inductance. Like the JPA, a large enough pump tone will modulate this inductance, coupling the pump (ω p ) to a signal (ω s ) and idler (ω i ) tone via frequency mixing such that ω s + ω i = 2ω p . Unlike the JPA however, the TWPA has no resonant structure so gain, bandwidth, and dynamic range are determined by the coupled mode equations of a nonlinear transmission line [23]. In addition to allowing more bandwidth and saturation power...

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“…This e¤ect has been used as the basis for a digital detector for qubit measurements [58]. Moreover, at a bias slightly below the critical point the nonlinear resonator can be used as a doubly degenerate parametric ampli…er [59,60,61]. We are interested in determining the magnetometer performance in both the linear and nonlinear regimes, and we will show in subsequent sections that parametric ampli…cation plays an important role in the ultimate ‡ux sensitivity.…”

Section: Theory Of Dispersive Magnetometer 431 Circuit Modelmentioning

confidence: 99%

SQUID magnetometry from nanometer to centimeter length scales

Hatridge

2010

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Information stored in magnetic …elds plays an important role in everyday life. This information exists over a remarkably wide range of sizes, so that magnetometry at a variety of length scales can extract useful information. Examples at centimeter to millimeter length scales include measurement of spatial and temporal character of …elds generated in the human brain and heart, and active manipulation of spins in the human body for non-invasive magnetic resonance imaging (MRI). At micron length scales, magnetometry can be used to measure magnetic objects such as ‡ux qubits; at nanometer length scales it can be used to study individual magnetic domains, and even individual spins. The development of Superconducting QUantum Interference Device (SQUID) based magnetometer for two such applications, in vivo prepolarized, ultra-low …eld MRI of humans and dispersive readout of SQUIDs for micro-and nanoscale magnetometry, are the focus of this thesis.Conventional MRI has developed into a powerful clinical tool for imaging the human body. This technique is based on nuclear magnetic resonance of protons with the addition application of three-dimensional magnetic …eld gradients to encode spatial information. Most clinical MRI systems involve magnetic …elds generated by superconducting magnets, and the current trend is to higher magnetic …elds than the widely used 1.5-T systems. Nonetheless, there is ongoing interest in the development of less expensive imagers operating at lower …elds. The prepolarized, SQUID detected ultra-low …eld MRI (ULF MRI) developed by the Clarke group allows imaging in very weak …elds (typically 132 T, corresponding to a resonant frequency of 5.6 kHz). At these low …eld strengths, there is enhanced contrast in the longitudinal relaxation time of various tissue types, enabling imaging of objects which are not visible to conventional MRI, for instance prostate cancer. We are currently investigating the contrast between normal and cancerous prostate tissue in ex vivo prostate specimens in collaboration with the UCSF Genitourinary Oncology/Prostate SPORE Tissue Core. In characterizing pairs of nominally normal and cancerous tissue, we measure a marked di¤erence in the longitudinal relaxation times, with an average value of cancerous tissue 0.66 times shorter than normal prostate tissue. However, in vivo imaging is required to de…nitively demonstrate the feasibility of ULF MR imaging of prostate cancer. To that end, we have worked to improve the performance of the system to facilitate human imaging. This is accomplished by increasing the prepolarizing …eld amplitude, and minimizing magnetic noise in the SQUID detector. We have achieved polarizing …elds as high 2 as 150 mT and SQUID e¤ective …eld noise below 1 fT Hz 1=2 , enabling us to demonstrate proof-of-principle in vivo images of the human forearm with 2 x 2 x 10 mm 3 resolution in 6 minutes.On a much smaller spatial scale, there is currently fundamental and technological interest in measuring and manipulating nanoscale magnets, particularly in the qua...

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Parametric amplification by unbiased Josephson junctions

Cited by 97 publications

References 12 publications

Dispersive magnetometry with a quantum limited SQUID parametric amplifier

Dispersive magnetometry with a quantum limited SQUID parametric amplifier

Traveling wave parametric amplifier with Josephson junctions using minimal resonator phase matching

SQUID magnetometry from nanometer to centimeter length scales

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