Quantum Fourier transform on photonic qubits using cavity QED

TL;DR

This paper introduces a method to perform quantum Fourier transforms on photonic qubits using a single atom-cavity system with time-delay feedback, enabling scalable quantum processing without active feedforward.

Contribution

It presents a novel protocol for implementing quantum Fourier transforms on multiple photons via cavity QED with no active feedforward control.

Findings

Numerical analysis shows feasibility with tens of photons.

Protocol achieves arbitrary controlled-phase gates.

Compatible with current cavity QED technology.

Abstract

We propose a quantum Fourier transform on photons in which a single atom-coupled cavity system mediates the photon-photon interactions. Our protocol utilizes time-delay feedback of photons and requires no active feedforward control. The time-delay feedback enables a single atom-cavity system to implement a quantum Fourier transform on an arbitrary number of photonic qubits on-the-fly, while rapid tuning of the atomic transition implements arbitrary controlled-phase gates. We analyze the performance of the protocol numerically and show that it can implement quantum Fourier transforms with tens of photons using state-of-the-art cavity quantum electrodynamics.