A simple optically controlled switch for nuclear spin-spin (inter-qubit) couplings in semiconductor-based quantum computers is described in Nature Communications this week. Such coupling is expected to have an essential role in the quantum gate operations of solid-state nuclear magnetic resonance (NMR) quantum computers in the future.

Two-quibit operation is an essential part of quantum computation, but difficult to achieve. Solid-state NMR quantum computing — one of the most advanced testbeds for quantum computation — requires a switchable inter-quibit coupling to control entanglements. Atsushi Goto and colleagues introduce optically controllable internuclear coupling in semiconductors providing a simple way of switching inter-qubit couplings in semiconductor-based quantum computers. The strength of coupling can be adjusted externally through light power, allowing easy implementation of on/off switching.