The Unruh effect was predicted in 1976.
As someone with no background in experimental physics I find it surprising this effect hasn't been measured yet. What are the experimental difficulties (and serious proposals) in measuring this effect?
The Unruh effect was predicted in 1976.
As someone with no background in experimental physics I find it surprising this effect hasn't been measured yet. What are the experimental difficulties (and serious proposals) in measuring this effect?
Detected Hawking–Unruh thermal bath temperature and acceleration needed for a detector to achieve registration of that vacuum temperature near detector surroundings and Unruh radiation, if any, is related by
$$a={\frac {2\pi ck_{\mathrm {B} }}{\hbar }}~T \tag 1 $$
So from (1) follows that if you want to register just $10^{−10}K$ minuscule thermal bath, you need to move at amazing $10^{10}~m/s^2$ (or in terms of $g$ $\approx 10^9~\text{g}$) acceleration. So basic problems follows :
the detector moving under a constant force and coupled to a one-dimensional scalar field [...] does not radiate
Even if it does,- this radiation should be minuscule and hence hardly distinguishable from other sources, like black body radiation of a moving detector itself (unless you move in $g$ comparable to the surface gravity of a typical black hole).
So, the conclusion is that, unless detector can simulate accelerations concieved by back hole,- no clean success of repeatable experiments are possible at "weak" conditions.
The conditions to measure the Unruh effect/ Unruh radiation are very difficult to produce with our current experimental capabilities. We need a relativistic accelerating frame to produce this radiation, creating very high acceleration and sustaining the acceleration for a long time is beyond our current experimental capability. Right now, there are already works done on quantum simulators to measure the Unruh effect, which may be of interest to you
[1] Quantum simulation of Unruh radiation, https://www.nature.com/articles/s41567-019-0537-1
[2] Quantum Simulation of Coherent Hawking-Unruh Radiation, https://arxiv.org/abs/1807.07504
[3] A quantum simulation of Unruh radiation, https://phys.org/news/2019-06-quantum-simulation-unruh.html