Quantum Optics Seminar: Etienne Corminboeuf

GKP State Generation Using a Strongly Coupled Optical Parametric Amplifier

Gottesman-Kitaev-Preskill (GKP) states are promising candidates for fault-tolerant universal quantum computing in continuous-variable systems. Although several methods to generate them have been proposed, high-fidelity implementation of such states is yet to be demonstrated in the optical domain. As the first part of this work, we analyze a GKP state generation protocol proposed by Yanagimoto et al., PRX Quantum 4, 010333 (2023) which makes use of a strongly coupled Optical Parametric Amplifier (OPA).  We quantify the protocol’s robustness to photon loss through numerical simulations and give analytical performance bounds. As the second part we then present a novel GKP generation approach, based on the Yanagimoto protocol and the so-called cat state breeding technique introduced by Vasconcelos et al, Opt. Lett. 35, 3261-3263 (2010). Our novel approach generalizes the breeding protocol to biased, imperfect cat states which can deterministically be generated using the OPA system from the previous protocol. We find that at low error rates, the novel approach yields GKP states with up to 3 dB more squeezing than the previous approach at comparable resources. Finally, we compare both approaches analyzed in this paper to a cavity QED approach introduced by Hastrup et al., Phys. Rev. Lett. 128, 170503 (2022), finding similar performance.