Charging a quantum spin network towards Heisenberg-limited precision

TL;DR

This paper introduces a cooperative protocol for charging quantum spin networks to their maximum energy state, achieving Heisenberg-limited precision through collective dynamics and phase transition crossing, validated on a quantum processing unit.

Contribution

The paper presents a novel cooperative charging protocol that leverages spin interactions and phase transitions to reach Heisenberg-limited precision in quantum spin networks.

Findings

Achieves magnetization fluctuations scaling as 1/N, reaching the Heisenberg limit.

Demonstrates scalable charging precision beyond the standard quantum limit.

Validates protocol on D-Wave quantum processor with up to 5612 spins.

Abstract

We present a cooperative protocol to charge quantum spin networks up to the highest-energy configuration, in terms of the network's magnetization. The charging protocol leverages spin-spin interactions and the crossing of a phase transition's critical point. Exploiting collective dynamics of the spin network, the cooperative protocol guarantees a precision advantage over any local charging protocol and leads to fluctuations (standard deviation) of the magnetization that scale as $1/N$, with $N$ being the number of spins in the network, i.e., the size of the spin battery. These findings mirror the Heisenberg limit for precision for parameter estimation in quantum metrology. We test our protocol on the D-Wave's Advantage quantum processing unit by charging sub-lattices with sizes ranging from $40$ to $5\,612$ spins, achieving the maximum magnetization and reaching a scalable charging precision beyond the standard quantum limit of $1/\sqrt{N}$.