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

Abstract

We construct an algorithm for suppressing the transitions of a quantum mechanical system, initially prepared in a subspace $\mathcal{P}$ 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 $ϵ$ in time $T$ increases as $T\exp [\sqrt{\log (T^2/ϵ)}]$, compared to $T^2{ϵ}^{-1}$ in the standard quantum Zeno effect.