Figure | Schematics of quantum correlation-enhanced DCS (QC-DCS). (IMAGE)
Caption
Figure | Schematics of quantum correlation-enhanced DCS (QC-DCS). a, DCS with intensity-correlated combs. b, Dual-comb results. c, Mid-infrared experimental data and simulation results. d, Broadband molecular spectra. In panel a, the signal and local combs mix on a photodetector (PD), generating dual-comb signals, while a separate idler comb is detected on a second PD to capture intensity noise correlated with the local comb. By subtracting the photocurrents, partial cancellation of shot noise in the dual-comb signals is achieved, lowering the noise floor in the spectrum derived from a fast Fourier transform (FFT) of the time-domain (t) signal. A low-pass filter (LPF) further suppresses background signals at the combs' repetition frequencies. The FFT yields dual-comb spectra with resolved comb lines. In this measurement, the signal comb power is only 1 nW, while the local comb power is 80 µW. The squeezed RF spectrum (orange) exhibits a reduced noise floor between 1 and 3.5 MHz compared to a standard quantum noise limit (SNL) dual-comb spectrum (blue). For the spectral results in panels b, c and d, a 10-cm-long gas cell filled with pure CH₄ at 2000 Pa (temperature: 275 K) was used.
Credit
Wan, Z., Chen, Y., Zhang, X. et al.
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CC BY