Zixing Liu

Quantum sensing leverages quantum resources to surpass the standard quantum limit, yet many existing protocols rely on the preparation of complex entangled states and Hamiltonian engineering, posing challenges for universality and scalability. Here, we report an experimental implementation of a universal butterfly metrology protocol, proposed in Kobrin et al. [A universal protocol for quantum-enhanced sensing via information scrambling, arXiv:2411.12794.] demonstrating a scrambling-based approach for quantum-enhanced sensing on a superconducting quantum processor. By exploiting many-body information scrambling, we observe quantum-enhanced phase sensitivity beyond the standard quantum limit, with a scaling consistent with a factor of 2 of the Heisenberg limit for system sizes of up to 10 qubits after a normalization process. Importantly, we experimentally establish a connection between the enhanced sensitivity and the dynamics of the out-of-time-order correlator, and show that the buildup of scrambling-induced genuine multipartite entanglement underlies the observed sensitivity enhancement. Our results demonstrate a scalable approach for quantum-enhanced sensing in interacting many-body quantum systems.

Quantum battery, as a novel energy storage device, offers the potential for unprecedented efficiency and performance beyond the capabilities of classical systems, with broad implications for future quantum technologies. Here, we experimentally demonstrate quantum charging advantage (QCA) in a scalable solid-state quantum battery. More specifically, we show how double-excitation Hamiltonians for two-level systems promote scalable QCA with standard methods. We effectively implement the collective evolution of quantum systems with two up to 12 battery cells in a superconducting quantum processor, and study the performance of quantum charging compared to its uncorrelated classical counterpart. The model considered is a linear chain of superconducting transmon qubits with only nearest-neighbor and pairwise interactions, which constitute the simplest model of a multi-cell quantum battery. Our results empirically realize substantial QCA without the necessity of adopting long-range and many-body interactions and showcase the quantum features of the QB charging processes with measurements of nonzero coherent ergotropy, incoherent ergotropy, and entanglement, revealing a promising prospect for further developments of efficient and experimentally feasible protocols for QCA.