Free-orbit experiment with laser interferometry X-rays

The Free-orbit Experiment with Laser Interferometry X-Rays^[1] belongs to a category of experiments evaluating whether macroscopic systems can be in superposition states, as was Schrodinger's belief, and it was proposed by the physicist Roger Penrose on his book "The road to reality" specifically to proove whether unconventional decoherence processes such as gravitationally induced decoherence or spontaneous wave-function collapse of a quantum system occur.

Configuration

 

Figure 2. Path of light in Michelson interferometer.

The experimental setup is basically a Michelson interferometer variation where one of the mirrors being very tiny and fixed on a micromechanical-oscillator. Originally the arms of the interferometer had to stretch into the hunderds of thousands of kilometers to achieve a photon rountrip-time comparable to the oscillator's period, but that meant that the experiment had to take place in-orbit, reducing its viability. A revised proposal ^[2] proposed to place the mirrors into high-finesse optical cavities that would trap the photons and become itself superposed with them, and achieve thus the desired delay.

There are various technological challenges but are within high-end laboratory capacity. The primary requirement is that the mass of the cavity remains as small as possible. According to the calculations it is estimated that a mass of roughly 10x14 atoms would be superposed, approximately nine orders of magnitude more massive than any superposition observed to date. The wavelength of the photons was calculated to be roughly 630nm so the reflecting surfaces can be as small as possible and yet avoid refraction and reflectivity issues. To avoid noise on the interferometer, the photon-emitter must have a low probability of emitting more than one photon each time, and that translates to very low absolute temprature for the experiment, in the order of 60μK. For similar reasons the experimental device has to be in ultra-high vacuum conditions. The micromechanical oscillator can be similar to the cantilevers in atomic force microscopes and the reflective surfaces typically used in similar high demaninding experiment pose no real challenge.

See also

• Penrose interpretation

References

1. Marshall, William; Christoph, Simon; Penrose, Roger; Bouwmeester, Dik (Sep 2003). "Towards quantum superpositions of a mirror". Physical Reviews Letters. 91 (13). American Physical Society: 130401–130405. doi:10.1103/PhysRevLett.91.130401. Retrieved 21 June 2014.
2. Cite error: The named reference name=SuperpositionsOfMirror2002 was invoked but never defined (see the help page).