Trapped Diamond Nanocrystals for Precision Gravitational Measurements and Tests of Quantum Gravity

Abstract

Gravity, which is the fundamental force with the most obvious impact in daily life, is also one of the least understood and most poorly measured. The Newtonian gravitational constant G, which quantitatively describes the strength of gravity, is one of the most imprecisely measured fundamental constants, and many of the measurements that have been made disagree with each other to an unexplained degree. Furthermore, theories of gravity have not been completely reconciled with quantum mechanics, the theory that we use to describe almost all physics on small size scales, from atoms and molecules to transistors and computer processors. The challenge in measuring gravity is that it is exceptionally weak among the fundamental forces; it only seems strong in daily life because the earth is so large. It is particularly hard to measure gravity on small size scales (e.g. smaller than bacteria), while quantum mechanics is difficult to observe on large size scales (e.g. much larger than a molecule). We propose to use a newly developed system, consisting of a nanoscale crystal of diamond levitated (trapped) in a magnetic field in a nearly perfect vacuum, to bridge the gap between gravity and quantum mechanics. The system takes advantage of the extreme isolation and sensitivity of the trapped particle combined with unique quantum properties of defect centers in diamond to provide measurements of G and quantum gravity that may be orders of magnitude more precise than existing measurements.

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