Fault-tolerant linear optical quantum computing with small-amplitude coherent states

TL;DR

This paper demonstrates that fault-tolerant linear optical quantum computing can be achieved with small coherent states, reducing resource requirements compared to single photon schemes, despite practical challenges.

Contribution

It introduces a fault-tolerant error correction scheme enabling universal quantum computing with small coherent states ($ ext{amplitude} > 1.2$), lowering resource overheads.

Findings

Fault-tolerance achievable with small coherent states

Resource use is significantly lower than single photon schemes

Photon loss effects are incorporated in Monte Carlo simulations

Abstract

Quantum computing using two optical coherent states as qubit basis states has been suggested as an interesting alternative to single photon optical quantum computing with lower physical resource overheads. These proposals have been questioned as a practical way of performing quantum computing in the short term due to the requirement of generating fragile diagonal states with large coherent amplitudes. Here we show that by using a fault-tolerant error correction scheme, one need only use relatively small coherent state amplitudes ($\alpha > 1.2$) to achieve universal quantum computing. We study the effects of small coherent state amplitude and photon loss on fault tolerance within the error correction scheme using a Monte Carlo simulation and show the quantity of resources used for the first level of encoding is orders of magnitude lower than the best known single photon scheme. %We study this reigem using a Monte Carlo simulation and incorporate %the effects of photon loss in this simulation.