Choose an Atomic Species

Lightest alkali. Large recoil energy makes imaging and trapping more demanding, so D1 gray molasses or related sub-Doppler cooling is especially important. Strong Feshbach resonances allow tunable interactions. Li-6 is the primary fermionic atom for strongly-correlated physics and BEC-BCS crossover experiments. Used in Li-Cs molecular assembly (Hood Lab, Purdue).

⁷Li: |F=1⟩ ↔ |F=2⟩ hyperfine qubit (803 MHz). ⁶Li: fermionic spin states used for many-body qubits.

Gehm (2003), Properties of ⁶Li [NCSU tech doc]

First atom used to achieve BEC (Ketterle group, MIT, 1995, Nobel Prize 2001). Yellow D-line at 589 nm. Larger scattering length suitable for BEC studies. Being revisited for molecule formation: NaLi, NaK, NaRb, NaCs.

|F=1⟩ ↔ |F=2⟩ hyperfine qubit (1772 MHz)

The Steck data sheet above is the canonical reference. Steck (2019, updated continuously).

K-40 is the only naturally abundant fermionic alkali; the standard atom for Fermi-Hubbard model simulations in optical lattices. K-39 has accessible Feshbach resonances for tuning interactions. All isotopes share the same 767/770 nm D-lines, diode laser accessible.

K-39: |1,−1⟩ ↔ |2,2⟩ clock-like transition

Rb-87 is the most widely used quantum computing atom, with large 6.835 GHz hyperfine splitting, convenient 780 nm lasers, and well-understood collisional properties. Rb is the backbone of the Harvard/QuEra and Pasqal neutral-atom ecosystem; Atom Computing instead uses alkaline-earth-like Yb for nuclear-spin qubits. Rb-85 has a Feshbach resonance for tunable interaction experiments.

Rb-87: |0,0⟩ ↔ |1,1⟩ or |1,−1⟩ ↔ |2,1⟩ "clock" qubit (6835 MHz)

steck.us, Rb-87 data sheet (v2.2)

Largest hyperfine splitting of the alkalis (9.193 GHz, defines the SI second). Excellent for optical tweezer work: heavy mass → low recoil → tighter confinement. Used in Li-Cs molecular assembly experiments (Hood Lab, Purdue). The 852 nm D2 line sits in a convenient region for diode lasers (DFB, ECDL).

|3,0⟩ ↔ |4,0⟩ "clock" transition (9193 MHz, field-insensitive at zero B-field)

steck.us, Cs data sheet

Sr has two laser-cooling stages: the broad 461 nm blue line (Doppler limit 770 μK) and the 689 nm red intercombination line (Γ/2π = 7.6 kHz, T_D = 0.18 μK). The 698 nm clock transition has a linewidth of ~1 mHz. Sr-87 (I = 9/2) gives 10 nuclear spin states for SU(N) physics and quantum simulation. Used in world-leading optical lattice clocks (Ye Lab, JILA).

Sr-87 nuclear spin qubit: |m_I = −9/2⟩ ↔ |m_I = −7/2⟩ via the 698 nm clock transition

Yb combines broad (399 nm, Γ/2π = 28 MHz) and narrow (556 nm, Γ/2π = 182 kHz) cooling lines with a mHz-linewidth clock transition at 578 nm. Yb-171 (I = 1/2) gives a very clean two-level nuclear-spin qubit in the electronic ground state. Magic wavelengths at 759 nm make optical lattice clocks insensitive to light shifts.

Yb-171: |m_I = +1/2⟩ ↔ |m_I = −1/2⟩ nuclear spin qubit (zero-field insensitive)

Dy-164 has the largest magnetic moment of any element (10 μ_B), enabling strong dipolar interactions and anisotropic collisional physics. Used for dipolar BEC, quantum droplets, and supersolid phases. Cooled on a broad 421 nm line; also has intercombination lines at 598 nm and 626 nm.

Er-168 has a magnetic moment of 7 μ_B and a rich level structure. Dipolar BEC demonstrated by Ferrier-Barbut/Pfau group (Stuttgart) and Grimm group (Innsbruck). Anisotropic scattering leads to distinctive many-body phases. Being explored for dipolar quantum droplets alongside Dy.