Individual Addressing in Quantum Computation through Spatial Refocusing

Separate addressing of individual qubits is a challenging requirement for
scalable quantum computation, and crosstalk between operations on neighboring
qubits remains as a significant source of noise for current experimental
implementation of multi-qubit platforms. We propose a scheme based on spatial
refocusing from interference of several coherent laser beams to significantly
reduce the crosstalk noise for any type of quantum gates. A general framework
is developed for the spatial refocusing technique, in particular with practical
Gaussian beams, and we show under typical experimental conditions, the
crosstalk-induced infidelity of quantum gates can be reduced by several orders
of magnitude with a moderate cost of a few correction laser beams.