Academic paper: ORCA research illuminates path to fault tolerance

ORCA’s long-term roadmap is focused on creating scalable fault-tolerant photonic quantum computers. On the path to achieving this, our team took a big first step with the publication of research into a new architecture that demonstrates significant improvements when dealing with challenges such as photon loss. Our research shows that fault-tolerant computers can be achieved with simpler resource states unlocked by our novel method for loss-resistant quantum information processing. This points towards a commercially viable way of building universal quantum computers.  

Role of resource states and measurement  

Resource states are entangled states of light, that serve as the fundamental fuel for photonic quantum computers. To perform computations, these states undergo a series of measurements in a specific pattern prescribed by the algorithm and underlying error-correction code. The choice of resource state is a critical element of the architectural design and is closely connected to the measurement protocol being used. 

Resource state generators, on the other hand, are modules within a photonic quantum computer that produce resource states. The efficiency of these generators is crucial, they need to be fast, reliable, and produce high-quality resource states. Scalability is another essential factor since a fault-tolerant photonic quantum computer requires many resource state generators. Furthermore, the practicality and feasibility of these generators are expected to increase when targeting simpler and smaller resource states. 

Impact of photon loss  

Photon loss is a critical design challenge in the development of fault-tolerant photonic quantum computers. It occurs when individual photons in a system are lost or absorbed by the surrounding environment, leading to entanglement degradation and loss of information.  

To tolerate photon loss, resource states need to have some built-in redundancy and structure. But while larger resource states can offer enhanced resilience, they also impose a heavier burden on the generation process.  

As quantum algorithms typically require an abundance of resource states, scaling a quantum architecture hinges on reducing the size of resource states to alleviate the complexity and resource demands of the scaled quantum system. 

ORCA’s novel approach to measuring resource states 

In photonic quantum computers, measurement modules serve as the counterparts to resource state generators, functioning as an ‘engine’ that consumes resource states to progress a computation. However, these measurement modules require specific types of resource states, just as different engines need different types of fuel. 

ORCA achieved a breakthrough by demonstrating that some of the burden can be shifted to how we measure resource states. By adding a modest level of complexity into the measurement protocol, traditionally regarded as the ‘easy’ component of the computer, we can unlock a category of simpler resource states. This advancement doesn’t compromise performance but rather redefines it, like designing a new model of an engine capable of operating on a cheaper type of fuel. 

Overall, with our state-of-the-art linear-optical measurement protocol, ORCA can unlock a new class of resource states and improve the overall photon-loss tolerance of a photonic quantum computer. 

 While there will be many breakthroughs required to reach universal quantum computers, this research is an exciting and promising step. 

 Read the academic paper