As the atom waves travel down the shaft, a second laser pulse will reunite the excited portion of each wave with its slower counterpart, and researchers will precisely determine the acceleration of the falling atom by measuring interference between the two parts of the wave.
Although MAGIS-100 will not be able to detect gravitational waves itself, it will test and develop technology for a future upgrade—one keen enough to pick up smaller spatial disturbances by dropping clouds of atom waves one kilometer apart.
Any tiny differences in the way the atom waves fall, for instance, will reveal the influence of a third party—such as undiscovered particles present in the space they traveled through.
A 10-meter-tall MAGIS prototype at Stanford University, currently one of the world's largest such instruments, has already created record-setting atom waves more than half a meter long; the Fermilab facility should produce waves of dozens of feet or more.
By exploiting the atoms' wavelike properties, the experiment will look for ripples in the bizarre quantum realm: potential fingerprints of missing dark matter and, in future iterations, new frequencies of gravitational waves.