Theoretical Design of Optimal Molecular Qudits for Quantum Error Correction

We pinpoint the key ingredients ruling decoherence in multispin clusters, and we engineer the system Hamiltonian to design optimal molecules embedding quantum error correction. These are antiferromagnetically coupled systems with competing exchange interactions, characterized by many low-energy states in which decoherence is dramatically suppressed and does not increase with the system size. This feature allows us to derive optimized code words, enhancing the power of the quantum error correction code by orders of magnitude. We demonstrate this by a complete simulation of the system dynamics, including the effect of decoherence driven by a nuclear spin bath and the full sequence of pulses to implement error correction and logical gates between protected states

New insights into the structural setting of North-Western offshore Sicily, Central Mediterranean

The North-Western offshore region of Sicily, located at the convergence zone of the Eurasian and African tectonic plates is characterized by intricate geological and tectonic setting. The opening of the Tyrrhenian backarc basin led to the development of Plio-Quaternary extensional basins, which are characterized by inversion structures. These structures located in the extensional basins of the examined region, have been identified after the interpretation of several multi-channel seismic reflection profiles. The structural and stratigraphic analysis was performed in compliance with the grid of seismic reflection profiles and the boreholes available in the public ViDEPI database. The in-depth analysis of these inverted tectonic structures is attention-worthy. We identified three basins in the area that highlight the inversion of variable intensity. They were all formed during the Early Pliocene rifting phase, paired with extensive volcanic activity; the basins also suffered a contractional episode afterward that resulted in their tectonic inversion. An inversion is registered within these basins involving the Plio-Quaternary deposits. One among these basins shows a strong impact of inversion on the entire sedimentary fill and it affects the sea floor. This contractional episode has been linked to the proximity of the Sicily Maghrebian thrust front (Argnani & Torelli, 2001) or a shift in the stress direction, signifying a compression in the N-S stress direction (Catalano & Milia., 1990; Sulli, 2000). Our analysis of inversion features is in agreement with previous studies in the NW offshore of Sicily and provides insights into the deformation history of this region

Quantum error correction with molecular spin qudits

Thanks to the large number of levels which can be coherently manipulated, molecular spin systems constitute a very promising platform for quantum computing. Indeed, they can embed quantum error correction within single molecular objects, thus greatly simplifying its actual realization in the short term. We consider a recent proposal, which exploits a spin qudit to encode the protected unit, and is tailored to fight pure dephasing. Here we compare the implementation of this code on different molecules, in which the qudit is provided by either an electronic or a nuclear spin (S, I > 1), coupled to a spin-1/2 electronic ancilla for error detection. By thorough numerical simulations we show that a significant gain in the effective phase memory time can be achieved. This is further enhanced by exploiting pulse-shaping techniques to reduce the leakage and/or the impact of decoherence during correction. Moreover, we simulate the implementation of single-qubit operations on the encoded states

Chiovenda a Parma

L'A. analizza l'insegnamento di Giuseppe Chiovenda a Parm