Alkaline-Earth Neutral-Atom Clock Qubit

A neutral-atom qubit subtype where information is encoded in long-lived nuclear-spin / clock-compatible states of alkaline-earth(-like) atoms (e.g., Sr, Yb), with metastable electronic manifolds used for manipulation, addressing, or transport.

Physics

Unlike alkali Rydberg platforms centered on hyperfine ground states, this architecture exploits the multielectron structure of alkaline-earth atoms. Proposals use separate optical potentials for (^1S_0) and (^3P_0) manifolds to decouple storage and control operations while preserving long coherence-compatible encoding states.

Hamiltonian

A minimal clock-qubit + Rydberg-control model in tweezer/lattice arrays:

$H={\sum }_i\frac{{\omega }_0}{2}{\sigma }_z^{(i)}+{\sum }_i\left[\frac{{\Omega }_i(t)}{2}{\sigma }_x^{(i)}+{\delta }_i(t)\frac{1-{\sigma }_z^{(i)}}{2}\right]+{\sum }_{i<j}{V}_{ij}{n}_i{n}_j$

where ${\omega }_0$ is the clock transition splitting (e.g., ${}^1{S}_0{\leftrightarrow }^3{P}_0$ manifold-encoded qubit), ${\Omega }_i$ and ${\delta }_i$ are local control fields, and $V_{ij}$ is a state-dependent interaction term (often Rydberg-mediated for entangling operations).

For clock-state encoding specifically, first-order magnetic sensitivity can be engineered to vanish at operating points:

$\frac{\partial {\omega }_0}{\partial B}\approx 0$

which is the central coherence advantage over many hyperfine encodings.

Figure

Why it matters

• Natural compatibility with optical-clock-grade internal states.
• Access to architecture-level control primitives not available in simpler alkali-only manifolds.
• Potential convergence path between neutral-atom quantum computing and quantum-metrology hardware stacks.

Key Metrics

Metric	Value	Notes	Fidelity reference
Core qubit encoding model	Long-lived nuclear-spin / clock-compatible states	Distinct from alkali hyperfine-only architecture assumptions	daley-2008-quantum-computing-with-alkaline-earth-atoms, daley-2011-state-dependent-lattices-for-quantum-computing-with-alkaline-earth-metal-atoms
Gate/control strategy	State-dependent lattices + metastable-state control; compatible with Rydberg entangling pathways	Architecture proposals plus subsequent alkaline-earth Rydberg experiments	daley-2011-state-dependent-lattices-for-quantum-computing-with-alkaline-earth-metal-atoms, madjarov-2020-high-fidelity-entanglement-and-detection-of-alkaline-earth-rydberg-atoms
Demonstrated alkaline-earth entanglement performance	High-fidelity two-atom entanglement demonstrated	Experimental support for practical alkaline-earth neutral-atom processing	madjarov-2020-high-fidelity-entanglement-and-detection-of-alkaline-earth-rydberg-atoms

Linked Papers

• daley-2008-quantum-computing-with-alkaline-earth-atoms
• daley-2011-state-dependent-lattices-for-quantum-computing-with-alkaline-earth-metal-atoms
• madjarov-2020-high-fidelity-entanglement-and-detection-of-alkaline-earth-rydberg-atoms

Related Entries

• rydberg-neutral-atom-qubit
• trapped-ion-qubit