Fig. 2: Sources and characterization of primary systematic shifts.
From: A lab-based test of the gravitational redshift with a miniature clock network
The error bars correspond to 1σ standard deviation. a The differential density shift at uop = 15Erec for a symmetric pair (2, 4) is evaluated by varying the atom number difference (ΔN). A linear fit yields a shift of −0.7(1) × 10−19 per 100 atom number difference. b Evaluation of the second-order Zeeman gradient arising from the magnetic field gradient (∂B/∂z ≈ 1.5 mG/cm). A linear fit yields a gradient of −95.3(1.0) × 10−19/cm. c Characterization of the BBR shift due to thermal gradients across the vacuum chamber. The inset is an illustration of the science chamber. To evaluate the BBR effect, a thermal gradient is introduced by varying the temperature difference between top and bottom viewports by up to ±1 K. A linear fit yields a BBR sensitivity of −4.2(1) × 10−18/cm per 1 K difference in our system. d Correlations between relative trap depth difference (δu) and differential lattice light shifts after subtraction of the residual spatial light shift gradient. u and (1 + δu)u correspond to the absolute trap depths for the ensemble pairs. e Evaluation of lattice light shift gradient at uop = 15Erec after removing contributions from δu shifts. A linear fit yields a gradient of −8.0(1.1) × 10−20/Erec/cm.
