Abstract
We present a compact current sensor based on a superconducting microwave lumped-element resonator with a nanowire kinetic inductor, operating at 4.2 K. The sensor is suitable for multiplexed readout in GHz range for large-format arrays of cryogenic detectors. The device consists of a lumped-element resonant circuit, fabricated from a single 4 nm-thick superconducting layer of niobium nitride. Thus, the fabrication and operation is significantly simplified in comparison to state-of-the-art current readout approaches. Because the resonant circuit is inductively coupled to the feed line the current to be measured can directly be injected without having the need of an impedance matching circuit, reducing the system complexity. With the proof-of-concept device we measured a current noise floor δImin of 10 pA/Hz1/2 at 10 kHz. Furthermore, we demonstrate the ability of our sensor to amplify a pulsed response of a superconducting nanowire single-photon detector using a GHz-range carrier for effective frequency-division multiplexing.
Highlights
We present a compact current sensor based on a superconducting microwave lumped-element resonator with a nanowire kinetic inductor, operating at 4.2 K
In case of voltage biased transition-edge sensors (TES) very small current changes needs to be precisely amplified, which is realized in state-of-the-art systems using superconducting quantum interference devices (SQUIDs)
Frequency-based multiplexing of TES arrays is realized by coupling the SQUIDs with additional resonant circuits [6,7] further increasing the complexity
Summary
We present a compact current sensor based on a superconducting microwave lumped-element resonator with a nanowire kinetic inductor, operating at 4.2 K. Using superconducting resonators with high quality factors (high Q) the effect of the nonlinearity can be boosted proportionally to the Q factor Potential applications of such devices are array-scalable magnetometers and current sensors, which could be an alternative to a SQUID-based readout schemes. Because of the used material the operation temperature needs to be far below the boiling temperature of liquid helium Their approach requires a large impedance matching circuit to feed the signal to be measured into the resonator, which for array applications may not be optimal. Another group demonstrated a tunable resonator based on NbTiN operated at 1.4 K [20]. To use their approach to multiplex arrays of detectors, a further impedance matching network is required
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