Heavy-matter-wave and ultra-sensitive interferometry: An opportunity for quantum-gravity becoming an evidence based research

    Solar Eclipse of 1919
(wikipedia)

Preamble 

   

Cool ideas in theoretical physics are ofter opaque for general reader whether if they are backed up with any experimental evidence in the real world. The success of LIGO (Laser Interferometer Gravitational-wave Observatory) definitely proven the value of interferometry for advancement of cool ideas of theoretical physics supported by real world measurable evidence. An other type of interferometry that could be used in testing multiple-different ideas from theoretical physics is called matter-wave interferometry or atom interferometry: It's been around decades but the new developments and increased sensitivity with measurement on heavy atomic system-waves will pave the technical capabilities to test multiple ideas of theoretical physics. 

Basic mathematical principle of interferometry

Usually interferometry is explained with device and experimental setting details that could be confusing. However,  one could explain the very principle without introducing any experimental setup.  The basic idea of of interferometry is that if a simple wave, such as $\omega(t)=\sin\Theta(t)$, is first split into two waves and reflected over the same distance, one with shifted with a constant phase, in the vacuum without any interactions. A linear combination of the returned waves $\omega_{1}(t)=\sin \Theta(t)$ and  $\omega_{2}(t)=\sin( \Theta(t) + \pi))$, will yield to zero, i.e.,  an interference pattern generated by $\omega_{1}(t)+\omega_{2}(t)=0$. This very basic principle can be used to detect interactions and characteristics of those interactions wave encounter over the time it travels to reflect and come back. Of course, the basic wave used in many interferometry experiments is the laser light and interaction we measure could be gravitational wave that interacts with the laser light i.e., LIGO's set-up.

Detection of matter-waves : What is heavy and ultra-sensitivity?

Each atomic system exhibits some quantum wave properties, i.e., matter waves. It implies a given molecular system have some wave signatures-characteristics which could be extracted in the experimental setting. Instead of laser light, one could use atomic system that is reflected similar to the basic principle. However, the primary difference is that increasing mass requires orders of magnitude more sensitive wave detectors for atomic interferometers. Currently heavy means usually above ~$10^{9}$ Da (comparing to Helium-4 which  is about ~4 Da), these new heavy atomic interferometers might be able to detect gravitational-interactions within quantum-wave level due to precisions achieved ultra-sensitive. This sounds trivial but experimental connection to theories of quantum-gravity, one of the unsolved puzzles in theoretical-physics appears to be a potential break-through. One prominent example in this direction is entropic gravity and wave-function collapse theories.  

Conclusion

Recent developments in heavy matter-wave interferometry could be leveraged for testing quantum-gravity arguments and theoretical suggestions. We try to bring this idea into general attention without resorting in describing experimental details. 

Further Reading & Notes

• Dalton, mass-unit used in matter-wave interferometry. 
• Atom Interferometry by Prof. Pritchard YouTube.
• Newton-Schrödinger equation.
• Papers of Kingsley R. W. Jones are also very novel in this direction. 
• A roadmap for universal high-mass matter- wave interferometry  Kilka et. al. AVS Quantum Sci. 4, 020502 (2022). doi
• Current capabilities as of 2022, atom interferometers can reach up to ~300 kDa.
• Testing Entropic gravity, arXiv. 
• NASA early stage ideas workshops : web-archive