Low-temperature Quantum Metrology Enhanced by Strong Couplings

TL;DR

This paper introduces a method to improve low-temperature quantum metrology by leveraging strong couplings, overcoming the error divergence seen in weak-coupling scenarios, and demonstrating polynomial scaling of precision with temperature.

Contribution

The study proposes using strong coupling effects via reaction-coordinate mapping to eliminate low-temperature error divergence in quantum metrology, revealing the importance of non-Markovianity.

Findings

Strong couplings induce noncanonical equilibrium states.

Metrology precision scales polynomially with temperature.

Weak coupling leads to exponential decay of precision at low temperatures.

Abstract

Equilibrium probes have been widely used in various noisy quantum metrology schemes. However, such an equilibrium-probe-based metrology scenario severely suffers from the low-temperature-error divergence problem in the weak-coupling regime. To circumvent this limit, we propose a strategy to eliminate the error-divergence problem by utilizing the strong coupling effects, which can be captured by the reaction-coordinate mapping. The strong couplings induce a noncanonical equilibrium state and greatly enhance the metrology performance. It is found that our metrology precision behaves as a polynomial-type scaling relation, which suggests the reduction of temperature can be used as a resource to improve the metrology performance. Our result is sharply contrary to that of the weakcoupling case, in which the metrology precision exponentially decays as the temperature decreases. Paving a way to realize a high-precision noisy quantum metrology at low temperatures, our result reveals the importance of the non-Markovianity in quantum technologies.