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. If successful, it is estimated that a mass of roughly 10¹⁴ atoms would have been superposed, approximately nine orders of magnitude more massive than any superposition observed to date (2003).

Configuration

 

Figure 2. A Michelson interferometer.

The proposed experimental setup is basically a Michelson interferometer variation for a single photon where one of the mirrors is 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] placed the mirrors into high-finesse optical cavities that trap the photon and become superposed with it, long enough, to achieve the desired delay.

There are various technological challenges but are within high-end laboratory capabilities. The primary requirement is that the mass of the cavity remains as small as possible. 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 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. 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. Various elaborate techniques have been proposedto "reset" the cavities to stable states before each repetition of the experiment.

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).