Entangled Dual-Comb Spectroscopy: Experimental Demonstration

Optical frequency combs have emerged as a cornerstone for a wide range of areas, including spectroscopy, ranging, optical clocks, time and frequency transfer, waveform synthesis, and communications. However, quantum mechanical fluctuations of the optical carrier impose fundamental performance limits on the precision of traditional laser frequency combs, particularly in their use for interferometry and spectroscopy.Entanglement is a quintessential quantum resource that has been harnessed to surpass the fundamental limits of classical systems. Here, we introduce and experimentally demonstrate entangled dual-comb spectroscopy (EDCS) that surmounts the fundamental limits of traditional frequency combs. EDCS builds on tailored entangled spectral structures of the frequency combs, enabling simultaneous detection of all comb lines below the standard quantum limit. Applying EDCS in gas detection, we achieve a boosted signal-to-noise ratio and broad bandwidth, rendering it particularly suited for dynamic chemical and biological sensing, where fast, precise measurements subject to power constraints are crucial. EDCS represents a new paradigm for quantum frequency combs, underscoring their prospects in a plethora of applications in precision metrology, spectroscopy, and timekeeping.