1. Dipartimento di Informatica, Facoltà di Scienze, Università di Verona, Ca' Vignal 2, Strada Le Grazie 15, 37134 Verona, Italy
2. School of Mathematics and Statistics, University of Glasgow, Glasgow G12 8QW, United Kingdom
3. Joint Quantum Centre (JQC) Durham-Newcastle, and School of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom