Experimental Investigation of Geometric Quantum Speed Limits in an Open Quantum System

TL;DR

This study experimentally investigates geometric quantum speed limits in an open quantum system, revealing how different dynamics and measures influence the fundamental bounds on quantum evolution times.

Contribution

It provides the first experimental analysis of quantum speed limits in open systems, comparing QFI and WY metrics under various decoherence conditions.

Findings

WY metric sets tighter QSL in Markovian dynamics

QSLs are sensitive to small fluctuations in spin magnetization

Crossovers between QSLs related to QFI and WY in non-Markovian regimes

Abstract

We studied geometric quantum speed limits (QSL) of a qubit subject to decoherence in an ensemble of chloroform molecules in a Nuclear Magnetic Resonance experiment. The QSL is a fundamental lower bound on the evolution time for quantum systems undergoing general physical processes. To do so, we controlled the system-reservoir interaction and the spin relaxation rates by adding a paramagnetic salt, which allowed us to observe both Markovian and non-Markovian open system dynamics for the qubit. We used two distinguishability measures of quantum states to assess the speed of the qubit evolution: the quantum Fisher information (QFI) and Wigner-Yanase skew information (WY). For non-Markovian dynamics and low salt concentrations, we observed crossovers between QSLs related to the QFI and WY metrics. The WY metric sets the tighter QSL for high concentrations and Markovian dynamics. We also show that QSLs are sensitive even to small fluctuations in spin magnetization.