Paper: A fluorescent-protein spin qubit (Nature, 4 Sep 2025)
In a nutshell
- Enhanced yellow fluorescent protein (EYFP) is realized as an optically addressable spin qubit supporting initialization, readout, and coherent control.
- At liquid-nitrogen temperature, the qubit shows ≈16 μs coherence under CPMG and up to ~20% spin contrast.
- Coherent control is maintained in mammalian cells, and room-temperature ODMR is demonstrated in E. coli with up to ~8% contrast.
What’s novel?
Unlike solid-state defects, this platform is genetically encodable, enabling one-to-one placement of a spin sensor within a few nanometres of a target protein via fusion constructs—bringing molecule-scale quantum sensing into living systems.
How it works (OADF/ODMR)
- OADF readout: a near-IR (~912 nm) pulse tailors triplet sublevel populations; a resonant microwave drives transitions that appear as ODMR contrast in time-delayed photoluminescence.
- Room-temperature ODMR: fast relaxation at 293 K is countered by 912-nm re-excitation that restores polarization and rescues ODMR contrast.
Key results
- Zero-field splitting: D ≈ (2π)×2.356 GHz; E ≈ (2π)×0.458 GHz.
- Coherence: ≈16 μs under CPMG at ~80 K.
- Room-temperature sensing: aqueous ODMR and DC-field differencing demonstrated.
- In-cell ODMR: E. coli shows room-temperature ODMR with reduced autofluorescence due to time-delayed readout.
- Sensitivity (upper-bound): AC in the μT·Hz−1/2 range at 80 K; room-temperature DC in the mT·Hz−1/2 range (normalization details apply).
Why it matters
A genetically encodable qubit promises molecule-level quantum sensing in living systems. Opportunities include EPR-like and NMR-like readouts of metalloprotein redox states, DEER-style distance constraints, and drug-binding mechanisms, potentially extending to interactions with 19F-containing drugs. Narrow room-temperature ODMR lines could also enable multiplexed bio-imaging.
My take for drug discovery
- Proximal functional readouts: fusion of EYFP-qubits to targets can report nm-scale changes (redox, paramagnetism, radical intermediates) as ODMR contrast, enabling mechanism-aware phenotypic screens.
- Quantum KPIs for target engagement: combine with 19F-containing drugs or spin-labelled ligands to quantify binding, conformational shifts, and residence time via frequency/contrast/relaxation metrics.
- Quantum overlays on cell phenotypes: augment mitochondrial activity, oxidative stress, and phase separation readouts with local B-field/temperature/electric-field proxies to sharpen hit triage and MoA deconvolution.
- Protein engineering lever: apply directed evolution to optimize optical/spin properties and build indication-specific sensor families.
Reference
Feder JS, Soloway BS, Verma S, et al. A fluorescent-protein spin qubit. Nature. 2025;645:73–81.
This article was edited by the Morningglorysciences team.
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