Exponentially-enhanced Weak-field Sensing with Quantum Stark Localization

TL;DR

This paper demonstrates that Stark-localized quantum probes with exponential field gradients can achieve exponential scaling in weak-field sensing precision, surpassing previous polynomial or super-polynomial limits.

Contribution

It introduces the concept of exponential gradient profiles in Stark probes, showing they enable exponential quantum Fisher information growth in both equilibrium and non-equilibrium regimes.

Findings

Quantum Fisher information grows exponentially with system size.

Exponential scaling persists in many-body and mid-spectrum eigenstates.

Non-equilibrium protocols with simple initial states retain exponential enhancement.

Abstract

Stark-localized quantum probes have recently been shown to enable quantum-enhanced weak-field sensing with polynomial or super-polynomial scaling. In this paper, we show that the spatial geography of the encoded field can elevate this advantage to a genuine exponential scaling. We study a one-dimensional Stark probe subject to an exponential gradient profile, \(V_j=e^{aj}\), and analyze its metrological performance in both equilibrium and non-equilibrium regimes, for single-particle and interacting many-body settings. In the equilibrium single-particle case, we derive an analytical lower bound showing that the quantum Fisher information grows exponentially with system size, and confirm numerically that this enhancement persists throughout the extended phase and at the localization transition. We further show that the same exponential scaling survives for mid-spectrum eigenstates and in the interacting many-body regime. This advantage remains intact under a fair resource analysis because the relevant preparation gap closes only algebraically, so the polynomial preparation overhead cannot offset the exponential gain in sensitivity. In the non-equilibrium regime, a simple product-state initialization followed by free evolution already retains exponential enhancement, eliminating the need for cooling, adiabatic preparation, or operation within a narrowly tuned sensing window. Finally, we outline a superconducting implementation based on flux-tunable transmon qubits with graded mutual inductive coupling to a common sensing bus. Our results identify exponentially graded Stark potentials as a distinct and experimentally plausible route to weak-field sensing with exponentially improving precision.