Daily relativistic effects

Albert Einstein came up his special and general relativity theory in 1905 and 1915, respectively. They have withstood various experimental tests, most amongst which are performed at high energy or on huge scale. This is because the SRT has significance usually at high speed while the GRT for massive objects. But, this is not the case any more. Actually, modern technologies have counted SRT for much long time in GPS. While for GRT, the impacts seem much far from daily life. Nevertheless, this recent work [Science 329 (5999), 1676-b.] made a breakthrough. It made use of atomic clocks whose accuracy can be achieved of 10^(-17) second.

Due to the lack of an accessible optical transition in ²⁷Al⁺ for efficient laser cooling and state detection, precision spectroscopy of these ions uses techniques developed in quantum information science. Here, an Al⁺ ion is sympathetically cooled through its Coulomb interaction with an auxiliary "logic" ion that is simultaneously held in the same linear radio-frequency (RF) Paul trap (14). The logic ion also helps prepare and detect the internal state of the Al⁺ ion via quantum logic protocols. In this work, the two Al⁺ clocks used a beryllium (⁹Be⁺) ion (14) and a magnesium (²⁵Mg⁺) ion (11), respectively, as the logic ion. The Al^{+ 1}S₀³P₀ clock transition with frequency f₀ near 1.121 PHz has a narrow (f = 8 mHz) natural linewidth and a corresponding intrinsic quality (Q) factor of f₀/f = 1.4 x 10¹⁷ that permits high sensitivity for detecting small frequency-shifting effects. However, the observed linewidth for the clock transition is limited by the linewidth of the probe laser. We probed the clock transition with a subhertz linewidth laser referenced to a high-finesse optical cavity (15). In the Al-Mg clock, with 300 ms probe duration we obtained a narrow, Fourier transform–limited linewidth, realizing a Q factor of 4.2 x 10¹⁴ with nearly 80% contrast (Fig. 1). This high-Q line provides the basis for high-stability clock operation and sensitivity to small frequency shifts.