Collisional quantum gates based on fermionic atoms have been realized independently by researchers in Germany and Switzerland. The gates are a long-proposed building block for quantum processors, but had been very challenging to create. Both teams’ gates achieve entangling operations with a fidelity above the theoretical threshold for quantum error correction – and could potentially be particularly useful for simulations of quantum chemistry. The potential of collisional quantum gates was proposed in the late 1990s by researchers such as Peter Zoller of the University of Innsbruck in Austria and Ivan Deutsch of the University of New Mexico in the US. The underlying principle is that the states of qubits are encoded into the spin states of atoms in an optical lattice. Then, gate operations between qubits are performed by manipulating interactions between the atoms’ wavefunctions.…