Time-Reversal-Based Quantum Metrology with Many-Body Entangled States

TL;DR

This paper demonstrates a quantum metrology protocol using time-reversal with many-body entangled states, achieving sensitivity beyond the standard quantum limit and approaching the Heisenberg limit with 350 atoms.

Contribution

Introduces a time-reversal protocol (SATIN) with many-body entangled states that surpasses spin squeezing limitations and does not require extreme measurement resolution.

Findings

Achieved 11.8 dB sensitivity improvement beyond SQL.

Demonstrated Heisenberg scaling with particle number.

Reached 12.6 dB from the Heisenberg Limit.

Abstract

In quantum metrology, entanglement represents a valuable resource that can be used to overcome the Standard Quantum Limit (SQL) that bounds the precision of sensors that operate with independent particles. Measurements beyond the SQL are typically enabled by relatively simple entangled states (squeezed states with Gaussian probability distributions), where quantum noise is redistributed between different quadratures. However, due to both fundamental limitations and the finite measurement resolution achieved in practice, sensors based on squeezed states typically operate far from the true fundamental limit of quantum metrology, the Heisenberg Limit. Here, by implementing an effective time-reversal protocol through a controlled sign change in an optically engineered many-body Hamiltonian, we demonstrate atomic-sensor performance with non-Gaussian states beyond the limitations of spin squeezing, and without the requirement of extreme measurement resolution. Using a system of 350 neutral $^{171}$Yb atoms, this signal amplification through time-reversed interaction (SATIN) protocol achieves the largest sensitivity improvement beyond the SQL ($11.8 \pm 0.5$~dB) demonstrated in any interferometer to date. Furthermore, we demonstrate a precision improving in proportion to the particle number (Heisenberg scaling), at fixed distance of 12.6~dB from the Heisenberg Limit. These results pave the way for quantum metrology using complex entangled states, with potential broad impact in science and technology. Potential applications include searches for dark matter and for physics beyond the standard model, tests of the fundamental laws of physics, timekeeping, and geodesy.