In situ amplification of spin echoes within a kinetic inductance parametric amplifier

Abstract

The use of superconducting microresonators together with quantum-limited Josephson parametric amplifiers has enhanced the sensitivity of pulsed electron spin resonance (ESR) measurements by more than four orders of magnitude. So far, the microwave resonators and amplifiers have been designed as separate components due to the incompatibility of Josephson junction–based devices with magnetic fields. This has produced complex spectrometers and raised technical barriers toward adoption of the technique. Here, we circumvent this issue by coupling an ensemble of spins directly to a weakly nonlinear and magnetic field–resilient superconducting microwave resonator. We perform pulsed ESR measurements with a 1-pL mode volume containing 6 × 10 7 spins and amplify the resulting signals within the device. When considering only those spins that contribute to the detected signals, we find a sensitivity of 2.8 × 1 0 3 spins / Hz for a Hahn echo sequence at a temperature of 400 mK. In situ amplification is demonstrated at fields up to 254 mT, highlighting the technique’s potential for application under conventional ESR operating conditions.

Three-wave-mixing quantum-limited kinetic inductance parametric amplifier operating at 6 T near 1 K

“…As detailed in Refs. [12,32], the inclusion of the SIF allows to partially decouple the resonator from the feedline at high frequency while maintaining a galvanic connection, needed to apply the necessary dc bias to the resonator for establishing 3WM processes. By embedding the resonator between two SIFs, we effectively create a Fabry-Perot cavity, with the SIFs acting as the microwave equivalent of Bragg mirrors [45].…”

“…However, their inherently low intensity poses a significant challenge for accurate measurement [3]. Within the microwave frequency spectrum, parametric amplifiers facilitate precise, rapid, and high-fidelity single-shot measurements for a broad spectrum of systems, including superconducting qubits [4,5], spin qubits based on quantum dots [6][7][8], spin ensembles [9][10][11][12], and nanomechanical resonators [13,14].…”

“…Both resonant [30] and traveling-wave [31] configurations have been successfully demonstrated. Notably, a significant breakthrough has been reported, demonstrating the use of dc bias current to activate a three-wave mixing process in kinetic inductance parametric amplifiers (3WM KIPA) [12,25,32,33]. However, until very recently, relatively little attention has been directed towards studying the magnetic field resilience of these systems [34][35][36].…”

Strong microwave squeezing above 1 Tesla and 1 Kelvin

“…1 b). To enable this configuration, we modify the KIPA design from those used in previous works 10 , 18 by adding a second port, allowing the pump and signal tones to be routed independently. We also make use of on-chip (superconducting) filters to suppress pump leakage (see Supplementary Note 3.B for further details).…”

“…We combine the KIPA with commercial microwave components and custom engineered device enclosures to minimize microwave losses, allowing us to achieve a direct measurement of − 7.8(2) dB of microwave vacuum noise squeezing. In addition, we show that high levels of squeezing can be maintained with the device operated in an in-plane magnetic field of up to 2 T, which permits its integration in applications such as spin resonance spectroscopy 8 , 18 , 19 and axion detection 4 , 9 . Finally, the high critical temperature ( ~ 13 K) of the superconducting film allows the squeezing of thermal states with the device operated at elevated temperatures, enabling vacuum level noise at a frequency of 6.2 GHz and a temperature of 1.8 K. These results show that quantum-noise-limited measurements can be performed at temperatures accessible using affordable pumped Helium-4 cryostats, a noise level that would otherwise only be attainable with comparatively expensive refrigeration technology.…”