# Perspective: Toward large-scale fault-tolerant universal photonic quantum computing

## TL;DR

This paper discusses how combining hybrid qubit-continuous variable methods with time-domain multiplexing can enable scalable, fault-tolerant universal photonic quantum computers with high operational bandwidth.

## Contribution

It introduces a hybrid approach and multiplexing technique to overcome key scalability challenges in photonic quantum computing.

## Key findings

- Hybrid qubit-continuous variable approach enables deterministic universal gates.
- Time-domain multiplexing allows large-scale quantum computing without circuit reconfiguration.
- All-optical systems can potentially operate beyond THz bandwidth.

## Abstract

Photonic quantum computing is one of the leading approaches to universal quantum computation. However, large-scale implementation of photonic quantum computing has been hindered by its intrinsic difficulties, such as probabilistic entangling gates for photonic qubits and lack of scalable ways to build photonic circuits. Here we discuss how to overcome these limitations by taking advantage of two key ideas which have recently emerged. One is a hybrid qubit-continuous variable approach for realizing a deterministic universal gate set for photonic qubits. The other is time-domain multiplexing technique to perform arbitrarily large-scale quantum computing without changing the configuration of photonic circuits. These ideas together will enable scalable implementation of universal photonic quantum computers in which hardware-efficient error correcting codes can be incorporated. Furthermore, all-optical implementation of such systems can increase the operational bandwidth beyond THz in principle, utimately enabling large-scale fault-tolerant universal quantum computers with ultra-high operation frequency.