Researchers demonstrates a variable-range Ising-type spin-spin interaction on
a naturally occurring 2D triangular crystal lattice of hundreds of spin-1/2 particles (Beryllium ions stored in a Penning trap), a computationally relevant scale more than an order of magnitude larger than existing experiments.
The Penning trap conﬁnes hundreds of spin-1=2 particles (qubits) on a two-dimensional (2D) triangular lattice. Each qubit is the valence electron spin of aBe+ ion. (lower) A Penning trap conﬁnes ions by use of a combination of static electric and magnetic ﬁelds. The trap parameters are conﬁgured so that laser-cooled ions form a triangular 2D crystal. A general spin-spin interaction HˆI is generated by a spin-dependent excitation of the transverse (along ˆz) motional modes of the ion crystal. This coupling is implemented with an optical dipole force (ODF) due to a pair of off-resonance laser beams (left side) with angular separation qR and difference frequency µR. Microwaves at 124GHz are directed to the ions with a horn and permit global spin rotations Hˆ B. (upper) A representative top-view resonance-ﬂuorescence image showing the center region of an ion crystal captured in the ions’ rest-frame; in the lab-frame the ions rotate a at wr= 2p 43:8 kHz. Fluorescence is an indication of the qubit spin-state (j”i bright, j#i dark); here, the ions are in the state j”i. The lattice constant is d0 20µm.