Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Picosecond-resolution single-photon time lens for temporal mode quantum processing



Chaitali Joshi, Ben Sparkes, Alessandro Farsi, Thomas Gerrits, Sae Woo Nam, Varun Verma, Sven Ramelow, Alex Gaeta


Techniques to control the spectro-temporal properties of quantum states of light at ultrafast time scales are crucial for several applications in quantum information science. In this work, we report an all-optical time lens based on Bragg-scattering four-wave mixing with picosecond resolution. Our system achieves a temporal magnification factor of 158 with single-photon level inputs, which is sufficient to overcome the intrinsic timing jitter of superconducting nanowire single-photon detectors. We demonstrate discrimination of two terahartz-bandwidth, single-photon level pulses with 2.1-picosecond resolution (electronic jitter corrected resolution of 1.25 ps). We draw on elegant tools from Fourier optics to further show that the time-lens framework can be extended to perform complex unitary spectro-temporal transformations by imparting optimized temporal and spectral phase profiles to the input waveforms. Using numerical optimization techniques, we show that a 4-stage transformation can realize an efficient temporal mode sorter that demultiplexes 10 Hermite-Gaussian (HG) modes. Our time-lens based framework represents a new toolkit for arbitrary spectro-temporal processing of single-photons, with applications in temporal mode quantum processing, high-dimensional quantum key distribution, temporal mode matching for quantum networks and quantum-enhanced sensing with time-frequency entangled states.


time lens, temporal mode sorting, single photon detection


Joshi, C. , Sparkes, B. , Farsi, A. , Gerrits, T. , Nam, S. , Verma, V. , Ramelow, S. and Gaeta, A. (2022), Picosecond-resolution single-photon time lens for temporal mode quantum processing, Optica, [online],, (Accessed May 26, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created March 28, 2022, Updated April 9, 2024