Granular Aluminum Parametric Amplifier beyond the gain- bandwidth limit
QUANTUM Seminar
Date
Tuesday, November 4, 2025 11:00 - 12:00
Speaker
Nicolas Zapata (Karlsruhe Institute for Technology (KIT) / DE)
Location
Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101)
Series
Seminar/Talk
Host
Johannes Fink
Contact
Superconducting-based parametric amplifiers have become essential
components for the detection and readout of microwave quantum circuits. Among
their different implementations, standing-wave amplifiers are particularly
attractive due to their ability to deliver high gain and quantum-limited noise
performance with flexible engineering and fabrication. However, their operation
near an instability point imposes a fundamental constraint: the instantaneous
bandwidth decreases with increasing amplifier gain, a trade-off commonly known
as the gainbandwidth limit. One approach to mitigate this limitation consists of
impedance engineering, which enables a tenfold bandwidth increase at the 20
dB gain levels typically required in quantum measurements [1]. In this work, we
implement a complementary approach based on two simultaneous parametric
drives that activate phase-preserving gain and frequency-conversion processes,
enabling parametric amplification without instability [2]. Realized in a granular
aluminum Bose-Hubbard dimer [3], this method achieves a fivefold bandwidth
enhancement at 20 dB gain, surpasses the conventional gainbandwidth limit up
to 25 dB, and maintains near-quantum-limited performance.
[1] O. Naaman. & J. Aumentado, PRX Quantum 3, 020201 (2022).
[2] A. Metelmann. et al., arXiv 2208.00024 (2022).
[3] N. Zapata. et al., Phys. Rev. Lett. 133, 262604 (2024).