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Speaker: Kevin O’Brien (MIT) – Title: Broadband quantum-limited amplification and near-ultrastrong light-matter coupling with superconducting circuits
May 1 @ 4:00 pm - 5:00 pm
Research Progress Meeting
Date: May 1, 2025
Time: 4:00- 5:00 pm
Location: Sessler Conference Room- 50A-5132 [In-Person and HYBRID]
Speaker: Kevin O’Brien (MIT)
Title: Broadband quantum-limited amplification and near-ultrastrong light-matter coupling with superconducting circuits
Abstract: Superconducting qubits are one of the leading quantum computing platforms in part due to the nonlinearity of the Josephson junction. High quantum efficiency broadband amplification is a key requirement for high fidelity qubit readout and thus implementing quantum error correction. We illustrate the modeling and design of high quantum efficiency broadband parametric amplifiers using our open source package JosephsonCircuits.jl [1]. These amplifiers are engineered to match the Floquet modes in the amplifier to the eigenmodes of the environment, eliminating a previously ubiquitous noise mechanism in broadband amplifiers [2]. We present the fabrication of such amplifiers using a high-Q qubit fabrication process with state of the art junction critical current uniformity. We detail the characterization of these amplifiers including the highest reported quantum efficiency for a traveling wave parametric amplifier [3] and future directions of on-chip integration and isolation. Finally, we show how qubits with quartic [4] rather than the familiar weakly anharmonic potential enable the first demonstration of near-ultrastrong nonlinear coupling [5] with applications in fast qubit readout [6] and gates.
[1] K. Peng, R. Poore, P. Krantz, D. E. Root, and K. P. O’Brien “X-parameter based design and simulation of Josephson traveling-wave parametric amplifiers for quantum computing applications” IEEE QCE22 (2022)
[2] K. Peng, M. Naghiloo, J. Wang, G. D. Cunningham, Y. Ye, and K. P. O’Brien “Floquet-Mode Traveling-Wave Parametric Amplifiers” PRX Quantum 3, 020306 (2022)
[3] J. Wang*, K. Peng*, G. D. Cunningham, A. Lombo, A. Yen, D. Zaidenberg, W. D. Oliver, K. P. O’Brien “High-Efficiency, Low-Loss Floquet-Mode Traveling-Wave Parametric Amplifier” arxiv 2503.11812 (2025)
[4] Y. Ye, K. Peng, M. Naghiloo, G. Cunningham, K. P. O’Brien “Engineering purely nonlinear coupling between superconducting qubits using a quarton” Physical Review Letters 127 (5), 050502 (2022)
[5] Y. Ye, J. B. Kline, A. Yen, G. Cunningham, M. Tan, A. Zang, M. Gingras, B. M. N., H. Stickler, K. Serniak, M. E. Schwartz, K. P. O’Brien “Near-ultrastrong nonlinear light-matter coupling in superconducting circuits” arXiv:2404.19199 (2024)
[6] Y. Ye, J. B. Kline, S. Chen, A. Yen, K. P. O’Brien “Ultrafast superconducting qubit readout with the quarton coupler” Science Advances 10 (41), eado9094 (2024)
https://lbnl.zoom.us/j/98854322464?pwd=K2tKUm1VZjRlV1J5RHE3cXdHQzRxdz09
Meeting ID: 988 5432 2464
Passcode: 142239