Fast feed-forward cancellation of laser phase noise for cold atom experiments

Lasers are key elements in numerous fields across science. Its technology has been evolving at an impressive rate for the past 60 years. Although great progress has been achieved, for experiment requiring high precision such as cold-atom quantum computing [1], lower noise is always desirable, especially for quantum gates with Rydberg atoms. The fidelity of the gate essentially relies on the stability of (i) the laser intensity, for which techniques are readily available, and (ii) the laser phase [2,3]. Solid-state lasers show remarkable performance both in terms of intensity and phase noise; however, their cost remains high and are not available for every wavelength. Therefore, techniques for reducing the noise of other lasers such as diode lasers are of interest. In this presentation, we report on a simple approach to quantify fast phase noise in laser sources and a feedforward technique for phase noise cancellation at high Fourier frequencies. Using this alloptical-fiber system, we successfully reduce phase noise by 30 dB for Fourier frequencies ranging from 2 MHz to 10 MHz. With its simple assembly, this system makes low phase noise laser light accessible to a greater number of researchers and stimulates experimental fields such as cold atom experiments. This system is ready to be implemented into Rydberg atom experiments and should allow for improved fidelity. I will present its scheme and discuss future upgrades of the system.

[1] Chew Y., Tomita T., Mahesh T.P., Sugawa S., de Léséleuc S., Ohmori K. Ultrafast energy exchange between two single Rydberg atoms on a nanosecond timescale. Nat. Photonics 16, 724 (2022).

[2] de Léséleuc S., Barredo D., Lienhard V., Browaeys A., & Lahaye T. Analysis of imperfections in the coherent optical excitation of single atoms to Rydberg states. Phys. Rev. A 97, 053803 (2018).

[3] Levine H., et al. High-Fidelity Control and Entanglement of Rydberg-Atom Qubits. Phys. Rev. Lett. 121, 123603 (2018).