Relatore: Davide Vodola (Università di Bologna)
The loss of qubits – the elementary carriers of quantum information – poses one of the fundamental obstacles towards the realization of large-scale and fault-tolerant quantum information processors. In this work, we describe how to cope with qubit losses in a quantum memory encoded in the Kitaev surface code. We review the general protocol [Stace et al, PRL 102, 200501, (2009)] that has been developed for correcting the surface code suffering from qubit loss and then we propose an experimental implementation of a full cycle of qubit-loss detection and correction on a minimal instance of topological surface code. This includes a quantum non-demolition measurement of a qubit-loss event followed, in the case of loss detection by the restoration of encoded logical information by mapping it onto a new quantum correcting code formed of a reduced number of qubits. The demonstrated methods are applicable to trapped atoms and ions, photons, superconducting qubits and they constitute essential building blocks for complete and scalable quantum error correction.