Ultrafast squeezed light, broadband generation and measurement

Over the past few decades, substantial progress in quantum optics, particularly squeezed-light generation, has enabled transformative applications, including quantum-enhanced metrology. Concurrently, ultrafast science has delivered tools to control and measure field-driven dynamics on sub-femtosecond time scales. Here, we extend squeezed light into the ultrafast regime by generating, the few-cycle synthesized squeezed light pulses spanning 0.33–0.73 PHz via a degenerate four-wave-mixing (FWM) process. We measure the squeezing using a metrology approach tailored to few-cycle pulses: spectral interference of temporally delayed channel pairs yields phase noise, while intensity noise is extracted from shot-to-shot variance and benchmarked against a coherent reference. Crucially, by scanning the relative delay τ among the three FWM inputs, we directly track real-time amplitude-noise dynamics: fluctuations are minimized at temporal overlap and increases for positive/negative delays, with the nonlinear generation window confined near 3 fs. We further demonstrate switching between amplitude and phase squeezing by altering the medium tilt, confirming tunable quantum-state control. Finally, spatiotemporal overlap of all channels enables ~5.3 fs squeezed waveforms, opening a route toward petahertz-scale secure quantum communication, ultrafast quantum information processing, and attosecond quantum encryption concepts.