Enhancing qubit readout fidelity with two-mode squeezing of the coherent measurement signal

Quantum Physics [Submitted on 16 Mar 2026] Enhancing qubit readout fidelity with two-mode squeezing of the coherent measurement signal Baleegh Abdo, William Shanks, Oblesh Jinka, J. R. Rozen The ability to perform high-fidelity quantum nondemolition qubit readout is pivotal for the realization of large and powerful quantum computers. Such readout of superconducting qubits is generally enabled by amplifying the weak dispersive measurement signals using phase-preserving quantum-limited Josephson amplifiers with sufficient gain to dilute the contribution of the added noise by the output chain. Here, we further enhance the qubit readout fidelity by (1) simultaneously measuring the two-mode squeezed states of the amplified readout signals at the signal and idler frequencies of the nondegenerate amplifier and (2) coherently combining them at the classical processing stage following a relative rotation that maximizes the signal to noise ratio of the qubit-encoded readout quadrature. Such readout scheme exhibits enhancement in the readout fidelity for all practical values of amplifier gain and noise added by the output chain and is fully compatible with frequency multiplexed setups used in large quantum processors. Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2603.15804 [quant-ph]   (or arXiv:2603.15804v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.15804 Focus to learn more Submission history From: Baleegh Abdo [view email] [v1] Mon, 16 Mar 2026 18:34:24 UTC (36,970 KB) Access Paper: HTML (experimental) view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)