NQontrol: An open-source platform for digital control-loops in quantum-optical experiments

TL;DR

NQontrol is an open-source digital control platform for quantum optics experiments, enabling scalable, flexible, and cost-effective control loops with high performance and user-friendly software.

Contribution

It introduces NQontrol, a versatile open-source control system based on ADwin hardware, combining high-speed locking loops with accessible software and GUI for quantum optics.

Findings

Supports eight simultaneous locking loops at 200 kHz

Provides five second-order filtering sections per channel

Offers a user-friendly Python-based software with web GUI

Abstract

Experiments in quantum optics often require a large number of control loops, e.g. for length-stabilization of optical cavities and control of phase gates. These control loops are generally implemented using one of three approaches: commercial (digital) controllers, self-built analog circuitry, or custom solutions based on Field Programmable Gate Arrays (FPGAs) and microcontrollers. Each of these approaches has individual drawbacks, such as high cost, lack of scalability and flexibility, or high maintenance effort. Here we present NQontrol, a solution based on the ADwin digital control platform that delivers eight simultaneous locking loops running with 200 kHz sampling frequency, and offers five second-order filtering sections per channel for optimal control performance. A comprehensive software package written in Python, together with a web-based graphical user interface (GUI), makes the system as easy to use as commercial products, while giving the full flexibility of open-source platforms.