Ultrafast, all-optical coherence of molecular electron spins in room-temperature, water solution

The tunability and spatial precision of paramagnetic molecules makes them attractive for quantum sensing. However, usual microwave-based detection methods have poor temporal and spatial resolution, and optical methods compatible with room-temperature solutions have remained elusive. Here, we utilize pump-probe polarization spectroscopy to initialize and track electron spin coherence in a molecule. Designed to efficiently couple spins to light, aqueous K2IrCl6 enables detection of few-picosecond free induction decay at room temperature and micromolar concentrations. Viscosity is found to strongly vary decoherence lifetimes. This work redefines the meaning of room-temperature coherence by improving experimental time resolution by up to five orders of magnitude. Doing so unveils a new regime of electron spin coherence, opening the door to new synthetic design and applications of molecular quantum bits., , , # Ultrafast, all-optical coherence of molecular electron spins in room-temperature, water solution

[https://doi.org/10.5061/dryad.v6wwpzh55](https://doi.org/10.5061/dryad.v6wwpzh55)

## Description of the data and file structure

In order to investigate ultrafast electron spin decoherence, five types of spectroscopy were used: pulse and continuous wave (CW) electron paramagnetic resonance (EPR), magnetic circular dichrosim (MCD), UV-Visible absorbance (UV-Vis), transient absorption (TA) and time-resolved Faraday ellipticity (TRFE), which was the main workhorse of the study.

### Files and variables

Data is organised into 5 main folders, each corresponding to the different types of spectroscopy detailed above. Throughout all datasets, missing values are denoted with NaN.

*EPR/*

All EPR data saved in the Bruker .DSC / .DTA format, which can be read using the free EasySpin Matlab package: [https://easyspin.org/](https://easyspin.org/)

The .DTA file contains the spectrum itself and is ...