Phase-Dependent Squeezing in Dual-Comb Interferometry

We measure phase-dependent Kerr soliton squeezing and anti-squeezing in the time-domain dualcomb interferograms generated using two independent frequency comb lasers. The signal appears as non-stationary quantum noise that varies with the fringe phase of the interferogram and dips below the shot-noise level by as much as 3.8 dB for alternating zero-crossings. The behavior arises from the periodic displacement of the Kerr squeezed comb by the coherent field of the second frequency comb, and is confirmed by a quantum noise model. These experiments support a route towards quantum-enhanced dual-comb timing applications and raise the prospect of high-speed quantum state tomography with dual-comb interferometry.