  Bound entanglement was shown to be activated [P. Horodecki \textit{et al.,}
Phys. Rev. Lett. \textbf{82,} 1056 (1999)] in the sense that the entanglement
of a spatially separated two-qutrit system can be increased with nonzero
probability via a sufficiently large number of preshared bound-entangled
states, local three-level controlled operations, and classical communications.
Here, we present a local quantum Zeno scheme for activating bound entanglement
which is based only on single-particle rotations and threshold measurements. In
our scheme, neither a large number of bound-entangled states nor controlled
operations are required, and classical communication is required only once at
the end of the protocol. We show that a single bound-entangled state is
sufficient for increasing the negativity of the target entangled state from
0.11 to 0.17, and by using four more bound-entangled states, negativity can be
made greater than 0.42 and the fidelity to the maximally entangled state
increases from 0.3 to 0.41, 0.50, 0.59, and 0.61. We believe our results are
important not only for quantum technologies but also for a better understanding
of quantum entanglement.
