Exponential time-scaling of estimation precision by reaching a quantum critical point

Quantum metrology refers to the use of quantum resources in parameter-estimation protocols, aiming at enhancing its precision. The quantum Fisher information is a key quantity in this context, setting the ultimate achievable precision with respect to available resources, such as the total time of the protocol. In this work, we report a scheme where the quantum Fisher information features an exponential scaling with the protocol duration. This is achieved by performing a periodic modulation of the coupling of a quantum critical system close to the its critical value. This modulation leads to an exponential growth of the excitation number in time. Relying on the precision bound derived by Garbe et al. [L. Garbe et al., Quantum Sci. Technol. 7, 035010 (2022)], we show that the quantum Fisher information inherits this exponential time scaling, which is corroborated by numerical simulations. Finally, the impact of dissipation and finite-size effects are analyzed, showing that the exponential time scaling is robust to dissipation, although its exponent decreases for larger values of the dissipation rate. Therefore, our work illustrates the novel metrological opportunities that quantum critical systems can offer.

Automated summary

This work presents a scheme where the quantum Fisher information exhibits exponential growth with the duration of the protocol by performing periodic modulation of the coupling of a quantum critical system near its critical value. Numerical simulations demonstrate the robustness of the exponential time scaling against dissipation.