Low-Latency Digital Signal Processing for Feedback and Feedforward in Quantum Computing and Communication

TL;DR

This paper presents an FPGA-based digital signal processing system enabling real-time feedback in quantum computing, achieving low latency to improve qubit control and error correction.

Contribution

The authors develop and demonstrate a fast FPGA-based system for real-time quadrature demodulation and feedback trigger generation in quantum systems.

Findings

Feedback trigger latency of 110 ns achieved

System effectively used for active qubit initialization

Potential for advanced feedback and feedforward algorithms

Abstract

Quantum computing architectures rely on classical electronics for control and readout. Employing classical electronics in a feedback loop with the quantum system allows to stabilize states, correct errors and to realize specific feedforward-based quantum computing and communication schemes such as deterministic quantum teleportation. These feedback and feedforward operations are required to be fast compared to the coherence time of the quantum system to minimize the probability of errors. We present a field programmable gate array (FPGA) based digital signal processing system capable of real-time quadrature demodulation, determination of the qubit state and generation of state-dependent feedback trigger signals. The feedback trigger is generated with a latency of $110\,\mathrm{ns}$ with respect to the timing of the analog input signal. We characterize the performance of the system for an active qubit initialization protocol based on dispersive readout of a superconducting qubit and discuss potential applications in feedback and feedforward algorithms.