ClusStaR

Large-scale cluster states as a flexible resource for quantum information processing

Photonic platforms represent a promising option for quantum computation since they can be operated mostly at room temperature, are compatible with existing photonic manufacturing processes, and when operated at telecom wavelengths, they can be easily connected within a quantum information processing network. Photons are vulnerable to loss and interact weakly, but can be measured with high detection efficiency and large bandwidth, and therefore are ideal for measurement-based quantum computation (MBQC) schemes. The continuous variable (CV) implementation of MBQC is particularly advantageous for its scalability potential and the possibility to realize fault-tolerant architectures. In fact, 2D cluster states, the corresponding universal CV resource state, have been generated with thousands of modes of squeezed light, and the sequential operation of single-mode and two-mode gates has been demonstrated, also by consortium members.

In ClusSTAR, we will theoretically and experimentally explore new cluster state topologies and both Gaussian and non-Gaussian operations on these, with the primary aim of finding more efficient gate implementations for CV-MBQC. For this purpose, we will upgrade our first-generation computing platform to allow for variable graph state connectivity and dimensionality through a controllable interferometer configuration, thereby making it possible to explore optimized gate teleportation designs with reduced noise. We will also add non-Gaussian operations through partial photon detection to enable studies of qualitatively different graph states. Non-Gaussianity is necessary for universal and fault-tolerant quantum computing.

Beyond investigating optimised graph topologies and gate implementations, the theoretical work in ClusSTAR will include development of new benchmarks for the multimode entanglement of cluster states which will be used e.g. to study possible strategies for error optimisation and mitigation. To enable theory partners to directly test ideas on the experimental platform, it will be made fully remotely accessible. Our vision beyond the lifetime of the project is to make the MBQC platform cloud-accessible to users outside the consortium with the aim of accelerating the developments towards fault-tolerant quantum computing.