  The era of practical terrestrial applications of gravity gradiometry begun in
1890 when Baron Lorand von E\"otv\"os, a Hungarian nobleman and a talented
physicist and engineer, invented his famous torsion balance - the first
practical gravity gradients measuring device. It was credited for the major oil
discoveries later in Texas (USA). A 100 years later Kasevich and Chu pioneered
the use of quantum physics for gravity gradient measurements. Since then
cold-atom gravity gradiometers, or matter-wave gravity gradiometers, had been
under development at almost every physics department of top-rated universities
around the globe. After another 30 years since the Kasevich and Chu publication
in 1992, which had led to the first ever quantum gravity gradiometer, the
corresponding research and development ceased from being profoundly active a
few years back. This article is an attempt to understand and explain what may
have happened to the Quantum Invasion into the area of applied physics and
precision engineering that traditionally has been occupied by non-quantum
technologies developed for about a 130 years of the history of gravity
gradiometry.
