Abstract: In quantum metrology, an ensemble of entangled qubits can be used to enhance the sensitivity in estimating external fields [1]. To realize entanglement-enhanced sensing, precise control of the dynamics in interacting qubits remains as a challenge since interactions that create metrologically useful entanglement can also cause thermalization and decohere the probe system. In this talk, we introduce our entanglement-enhanced sensing scheme that is robust against spatially inhomogeneous always-on Ising interactions [2]. Our strategy is to tailor coherent quantum dynamics employing the Hilbert-space fragmentation (HSF) [3], a recently recognized mechanism that evades thermalization. Specifically, we analytically show that the emergent HSF in the two-dimensional transverse field Ising model [4,5] enables us to design a probe state that can be used to measure a weak transverse field with the Heisenberg-limited sensitivity without suffering from thermalization.
[1] C. L. Degen, F. Reinhard, and P. Cappellaro. Rev. Mod. Phys., 89, 035002 (2017).
[2] A. Yoshinaga, Y. Matsuzaki, and R. Hamazaki. arXiv:2211.09567 (2022).
[3] S. Moudgalya, B. A. Bernevig, and N. Regnault, Rep. Prog. Phys., 85, 086501 (2022).
[4] A. Yoshinaga, H. Hakoshima, T. Imoto, Y. Matsuzaki, and R. Hamazaki, Phys. Rev. Lett., 129, 090602, (2022).
[5] O. Hart and R. Nandkishore. arXiv:2203.06188 (2022).