# A Dual One-way Doppler Cancellation Scheme for Enhanced Gravitational Redshift Tests

## TL;DR

The paper introduces a simplified dual one-way Doppler cancellation scheme for gravitational redshift tests that enhances sensitivity and reduces complexity in satellite-ground clock experiments, enabling more precise fundamental physics tests.

## Contribution

It proposes a novel two-link frequency comparison method that doubles redshift sensitivity and halves engineering complexity compared to traditional triple-link schemes.

## Key findings

- Reduces engineering complexity by 50%
- Doubles gravitational redshift signal sensitivity
- Residual systematic errors below 10^{-17}

## Abstract

Gravitational redshift is an important prediction of General Relativity (GR). We propose a novel dual one-way frequency comparison scheme for gravitational redshift tests in satellite-ground clock experiments. Unlike conventional triple-link Doppler cancellation methods, our approach requires only two optical links, an uplink and a downlink, with Doppler data recorded independently at the satellite and ground station, respectively. Crucially, coherent combination of these measurements suppresses first-order Doppler frequency shift to second order while doubling the gravitational redshift signal. This scheme reduced engineering complexity (50$\%$ fewer links) and amplified redshift sensitivity with a factor of 2 for satellite-ground clock comparison. The scheme's viability hinges on high-precision clock synchronization ($\leq$ 0.1 ns for $10^{-18}$ clock comparison), which is potentially achievable via state-of-the-art time-transfer techniques. Systematic error analysis confirms residual Doppler, atmospheric, and Shapiro shifts remain below $10^{-17}$ for optimized orbits, establishing this scheme as a useful tool for probing fundamental physics beyond GR.