Preserving Quantum States using Inverting Pulses: A Super-Zeno Effect

We construct an algorithm for suppressing the transitions of a quantum mechanical system, initially prepared in a subspace P of the full Hilbert space of the system, to outside this subspace by subjecting it to a sequence of unequally spaced short-duration pulses. Each pulse multiplies the amplitude of the vectors in the subspace by -1. The number of pulses required by the algorithm to limit the leakage probability to γ in time T increases as Texp⁡[log⁡(T²/γ)], compared to T²γ^-1 in the standard quantum Zeno effect.