Quantum Confocal Microscopy in Fock Space with a 19 dB Metrological Gain

• URL: http://arxiv.org/abs/2602.23254v1
• Date: Thu, 26 Feb 2026 17:27:45 GMT
• Title: Quantum Confocal Microscopy in Fock Space with a 19 dB Metrological Gain
• Authors: Ziyue Hua, Chuanlong Ma, Yilong Zhou, Yifang Xu, Zi-Jie Chen, Weizhou Cai, Jiajun Chen, Lintao Xiao, Hongwei Huang, Weiting Wang, Hekang Li, Haohua Wang, Ming Li, Chang-Ling Zou, Luyan Sun,
• Abstract summary: We introduce quantum confocal microscopy in Fock space.<n>First lens deterministically focuses a coherent state into a quantum probe with a tightly concentrated photon-number distribution.<n>Second lens maps the metrological information back to the vacuum state for efficient readout.
• Score: 14.259530170243474
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Quantum metrology promises measurement precision beyond classical limits by exploiting large-scale quantum states, yet realizing this advantage faces two fundamental challenges: the deterministic preparation of non-trivial quantum probes and the efficient extraction of metrological information in high-dimensional Hilbert spaces. Here, we introduce quantum confocal microscopy in Fock space that simultaneously resolves both challenges. Drawing a direct analogy between classical wave optics and quantum state evolution in a bosonic mode, we construct a confocal system with two Fock-space lenses. The first lens deterministically focuses a coherent state into a quantum probe with a tightly concentrated photon-number distribution, while the second lens maps the metrological information back to the vacuum state for efficient readout. Using a superconducting circuit QED platform, we prepare focused probe states with mean photon numbers up to ${N} = 500$, achieving a 21.5$\pm$1.1 dB compression of the photon-number uncertainty relative to a coherent state, with a scalable quantum circuit of $\mathcal{O}(1)$ operational depth. We demonstrate a displacement sensitivity scaling as $N^{-0.416}$, approaching the Heisenberg scaling ($N^{-0.5}$), and achieve a record metrological gain of 19.06$\pm$0.13 dB beyond the standard quantum limit. This work establishes quantum confocal microscopy as a scalable and practical framework for quantum-enhanced precision measurement, readily extendable to other bosonic platforms and high-dimensional quantum many-body systems.

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