doi:10.1039/d1sc00564bengGimeno, IUrtizberea, ARoman-Roche, JZueco, DCamon, AAlonso, PJRoubeau, OLuis, FBroad-band spectroscopy of a vanadyl porphyrin: a model electronuclear spin quditART-2021-123407We explore how to encode more than a qubit in vanadyl porphyrin molecules hosting a S = 1/2 electronic spin coupled to a I = 7/2 nuclear spin. The spin Hamiltonian and its parameters, as well as the spin dynamics, have been determined via a combination of electron paramagnetic resonance, heat capacity, magnetization and on-chip magnetic spectroscopy experiments performed on single crystals. We find low temperature spin coherence times of micro-seconds and spin relaxation times longer than a second. For sufficiently strong magnetic fields (B > 0.1 T, corresponding to resonance frequencies of 9-10 GHz) these properties make vanadyl porphyrin molecules suitable qubit realizations. The presence of multiple equispaced nuclear spin levels then merely provides 8 alternatives to define the ''1'' and ''0'' basis states. For lower magnetic fields (B < 0.1 T), and lower frequencies (<2 GHz), we find spectroscopic signatures of a sizeable electronuclear entanglement. This effect generates a larger set of allowed transitions between different electronuclear spin states and removes their degeneracies. Under these conditions, we show that each molecule fulfills the conditions to act as a universal 4-qubit processor or, equivalently, as a d = 16 qudit. These findings widen the catalogue of chemically designed systems able to implement non-trivial quantum functionalities, such as quantum simulations and, especially, quantum error correction at the molecular level.2021http://zaguan.unizar.es/record/10839710.1039/d1sc00564bhttp://zaguan.unizar.es/record/108397oai:zaguan.unizar.es:108397info:eu-repo/grantAgreement/ES/DGA/E09-17R-Q-MADinfo:eu-repo/grantAgreement/ES/DGA/E31-17Rinfo:eu-repo/grantAgreement/EC/H2020/862893/EU/Molecular spin qudits offering new hope for quantum computing/FATMOLSThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 862893-FATMOLSinfo:eu-repo/grantAgreement/ES/MICINN/CTQ2015-64486-Rinfo:eu-repo/grantAgreement/ES/MICINN/CTQ2015-68370-Pinfo:eu-repo/grantAgreement/ES/MICINN/MAT2017-86826-Rinfo:eu-repo/grantAgreement/ES/MICINN/PCI2018-093116info:eu-repo/grantAgreement/ES/MICINN/PGC2018-098630-B-I00info:eu-repo/grantAgreement/ES/MICINN/RTI2018-096075-B-C21CHEMICAL SCIENCE 12, 15 (2021), 5621-5630byhttp://creativecommons.org/licenses/by/3.0/es/info:eu-repo/semantics/openAccess