Quantum Sensing with Triplet Pair States: A Theoretical Study

TL;DR

This theoretical study models the quantum sensing capabilities of triplet pair states in pentacene dimers, showing potential advantages over monomers for detecting small nuclear spin ensembles at the nanoscale.

Contribution

It introduces a model for the sensing efficacy of triplet pair states in pentacene dimers, highlighting their superior interaction cross-section and sensitivity in low magnetic fields.

Findings

Dimer architecture offers better interaction cross-section than monomers.

Sensitivity is optimized at low magnetic fields and increases with pulse number.

Both architectures are comparable for single-spin detection.

Abstract

Molecular quantum sensors represent a promising frontier for the detection of nuclear magnetic resonance signals and alternating current magnetic fields at the nanoscale, potentially reaching single-proton sensitivity. Although the triplet states of molecular pentacene provide a viable sensing architecture, the triplet pair states produced by singlet fission of pentacene dimers could enable more flexible quantum manipulations through entanglement. In this work, we model the quantum sensing efficacy of a spin-polarized quintet manifold in a photoexcited pentacene dimer generated via intramolecular singlet fission. Using a Lindblad master equation approach, we simulate the evolution of the triplet pair state under standard dynamical decoupling sequences, including spin echo, XY4, and XY8 and provide a direct performance comparison to the traditional pentacene monomer benchmark. While both architectures exhibit comparable sensitivity for isolated single-spin detection, our findings indicate that the dimer architecture provides a superior interaction cross-section for detecting small ensembles of nuclear spins. Analytical expressions derived for fluorescence modulation demonstrate that sensitivity is optimized in the low-magnetic field regime and scales with the number of pulses in the sensing protocol. This study establishes a theoretical baseline for utilizing high-spin multi-excitonic states as chemically tunable, high-sensitivity quantum probes.