Abstract
One of the most important tasks in modern quantum science is to coherently control and entangle many-body systems, and to subsequently use these systems to realize powerful quantum technologies such as quantum-enhanced sensors. However, many-body entangled states are difficult to prepare and preserve since internal dynamics and external noise rapidly degrade any useful entanglement. Here, we introduce a protocol that counterintuitively exploits inhomogeneities, a typical source of dephasing in a many-body system, in combination with interactions to generate metrologically useful and robust many-body entangled states. Motivated by current limitations in state-of-the-art three-dimensional (3D) optical lattice clocks (OLCs) operating at quantum degeneracy, we use local interactions in a Hubbard model with spin-orbit coupling to achieve a spin-locking effect. In addition to prolonging inter-particle spin coherence, spin-locking transforms the dephasing effect of spin-orbit coupling into a collective spin-squeezing process that can be further enhanced by applying a modulated drive. Our protocol is fully compatible with state-of-the-art 3D OLC interrogation schemes and may be used to improve their sensitivity, which is currently limited by the intrinsic quantum noise of independent atoms. We demonstrate that even with realistic experimental imperfections, our protocol may generate $\sim10$--$14$ dB of spin squeezing in $\sim1$ second with $\sim10^2$--$10^4$ atoms. This capability allows OLCs to enter a new era of quantum enhanced sensing using correlated quantum states of driven non-equilibrium systems.
Highlights
A major frontier of contemporary physics is the understanding of nonequilibrium behaviors of many-body quantum systems and the application of these behaviors toward the development of novel quantum technologies with untapped capabilities [1]
We describe a scheme that can lead to metrological advances in state-of-the-art optical lattice clocks (OLCs) through direct use of quantum entanglement by harnessing the interplay between nominally undesirable collisions and spin-orbit coupling (SOC)
The spin and one-axis twisting (OAT) models agree in the regime of weak SOC with B ∼ J sin(φ/2) f U, and exhibit different squeezing behaviors outside this regime as single-particle spin dephasing can no longer be treated as a weak perturbation to the spinlocking interactions
Summary
A major frontier of contemporary physics is the understanding of nonequilibrium behaviors of many-body quantum systems and the application of these behaviors toward the development of novel quantum technologies with untapped capabilities [1]. This scheme is made possible in the weak SOC regime by the formation of an interaction-energy gap that suppresses the SOC-induced population transfer from the exchange-symmetric Dicke manifold (spanned by spin-polarized and noninteracting states) to the remainder of Hilbert space. The new generation of 3D optical lattice systems have fully quantized motional degrees of freedom [4], allowing for precise control of collisional interactions We demonstrate how these interactions can naturally give rise to metrologically useful correlated many-body fermionic states, opening a path to generate entanglement, and harness it to achieve a quantum advantage in a world-class sensor. Such an advance will deliver gains to real-world applications, including timekeeping, navigation, telecommunication, and our understanding of the fundamental laws of nature [42]
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