Gaussian Approximation Accurately Simulates Gottesman-Kitaev-Preskill State Preparation with Loss

The creation of robust quantum computers relies on the ability to generate complex quantum states, and a particularly promising approach involves creating Gottesman-Kitaev-Preskill (GKP) states using a technique called cat breeding. Olga Solodovnikova, Ulrik L. Andersen, and Jonas S. Neergaard-Nielsen, all from the Center for Macroscopic Quantum States at the Technical University of Denmark, have investigated how imperfections in this process, specifically optical loss, impact the reliable creation of these vital states. Their research demonstrates that even small amounts of light loss significantly reduce the success rate of cat breeding, and exceeds a critical threshold of four percent, preventing the generation of fault-tolerant GKP states necessary for practical quantum computation. By developing a new simulation method, the team provides crucial insight into the limitations of this technique and establishes a benchmark for improving the resilience of future quantum technologies.

These states, which encode quantum information in the continuous properties of light, require precise control over quantum systems, and researchers are actively developing methods for their reliable generation. The method represents the quantum state of light as a combination of simpler Gaussian shapes, significantly reducing the computational demands of modeling the complex interactions within the cat breeding protocol. Specifically, the results show that loss exceeding four percent prevents the preparation of a GKP state suitable for fault-tolerant quantum computing. By employing a sophisticated simulation framework, the team has quantified the impact of optical loss on the success probability of grid state creation, highlighting the sensitivity of this approach to practical limitations. The open-source availability of the simulation code facilitates further research and development, allowing other researchers to explore methods for mitigating the effects of loss and improving the robustness of GKP state preparation. Future work could investigate combining approximate GKP states with other quantum states to enhance grid state generation and overcome these limitations.