  Localization of wavefunctions is arguably the most familiar effect of
disorder in quantum systems. It has been recently argued [[V. Khemani, R.
Nandkishore, and S. L. Sondhi, Nature Physics, 11, 560 (2015)] that, contrary
to naive expectation, manipulation of a localized-site in the disordered medium
may produce a disturbance over a length-scale much larger than the
localization-length $\xi$. Here we report on the observation of this nonlocal
phenomenon in electronic transport experiment. Being a wave property,
visibility of this effect hinges upon quantum-coherence, and its spatial-scale
may be ultimately limited by the phase-coherent length of the disordered
insulator. Evidence for quantum coherence in the Anderson-insulating phase may
be obtained from magneto-resistance measurements which however are useful
mainly in thin-films. The technique used in this work offers an empirical
method to measure this fundamental aspect of Anderson-insulators even in
relatively thick samples.
