Quantum-inspired interferometry with chirped laser pulses

Interference is a defining feature of both quantum and classical theories of light, enabling the most precise measurements of a wide range of physical quantities including length(1) and time(2). Quantum metrology exploits fundamental differences between these theories for new measurement techniques and enhanced precision(3,4). Advantages stem from several phenomena associated with quantum interferometers, including non-local interference(5,6), phase-insensitive interference(7), phase super-resolution and super-sensitivity(8-10), and automatic dispersion cancellation(6,11,12). However, quantum interferometers require entangled states that are in practice difficult to create, manipulate and detect, especially compared with robust, intense classical states. In the present work, we report an interferometer based on chirped femtosecond laser pulses and classical nonlinear optics showing all of the metrological advantages of the quantum Hong-Ou-Mandel interferometer(7), but with 10 million times more signal. Our work emphasizes the importance of delineating truly quantum effects from those with classical analogues(10,13,14), and shows how insights gained from quantum mechanics can inspire novel classical technologies.