Molecular MOC

Curated map of Zoo entries in the Molecular family.

Entries

Entry	Type	Status
molecular-qubit	qubit	demonstrated
nuclear-magnetic-resonance-qubit	qubit	demonstrated
polar-molecule-qubit	qubit	demonstrated

Composition

• qubit: 3

Conceptual anchors

• coherence-time-hierarchy is the right comparison frame here, because molecular platforms compete less on raw gate speed and more on how chemical design reshapes dephasing channels and extends usable spin coherence.
• spin-orbit-coupling-for-qubit-control captures one of the central molecular design tensions: stronger ligand-field and spin-orbit structure can unlock richer control, but usually at the price of opening additional relaxation and dephasing pathways.
• divincenzo-criteria explains why this family remains strategically interesting but still immature, because synthetic tunability is strong while scalable entangling gates and qubit-specific readout remain the limiting criteria.

Family structure

• molecular-qubit is the chemistry-designed solid-state spin branch: ligand fields and molecular synthesis shape the spin Hamiltonian.
• polar-molecule-qubit is the trapped-particle branch: rotational states carry the qubit and electrically induced dipoles provide entangling interactions.
• nuclear-magnetic-resonance-qubit is the ensemble-computing branch: nuclear spins inside molecules are controlled spectroscopically, but room-temperature demonstrations use pseudo-pure ensembles rather than individually addressable pure-state qubits.
• These are genuinely different hardware models. Their shared label is molecular degrees of freedom, not a shared readout stack or scaling architecture.

Molecular platform routing table

Branch	Logical degree of freedom	Interaction / control route	Readout model	Decisive scaling bottleneck
molecular-qubit	Electronic spin states engineered by ligand field, anisotropy, and hyperfine structure	Microwave spin control; proposed resonator and spin-photon interfaces	Ensemble control remains common; single-molecule readout is emerging	No standard scalable two-qubit coupling and readout stack yet
polar-molecule-qubit	Rotational and hyperfine states of individually trapped molecules	Switchable electric dipole exchange, naturally producing iSWAP-family gates; see sqrt-swap-as-universal-gate	State-selective survival detection in optical tweezers	Molecule assembly, cooling, loss, and parallel control
nuclear-magnetic-resonance-qubit	Nuclear spins within an ensemble of molecules	RF pulses plus intramolecular scalar $J$-coupling	Bulk ensemble magnetization	Pseudo-pure-state signal falls exponentially and cannot support single-shot error correction

Use this table as a routing test: chemical synthesis alone points to the first branch, individually trapped dipolar rotors to the second, and bulk spectroscopic ensembles to the third. A new molecular entry should not be merged into an existing branch merely because its carrier is a molecule.

The three branches should remain separate in comparisons: chemistry-designed spin registers, trapped polar rotors, and ensemble NMR solve different problems and have radically different scaling limits.