Following the 2012 discovery by our experimental colleagues in Delft of Majorana fermions in superconducting nanowires, we developed a method to use these charge-neutral quasiparticles as qubits in a quantum computer. By coupling the Majoranas to a Cooper pair box it is possible to initialize, manipulate, and read-out the quantum information. This hybrid approach uses existing superconducting technology and is now being implemented in Delft, as well as in competing laboratories, to perform the first braiding operation – which is the "holy grail" of the field. Several of the students and postdocs of the Instituut-Lorentz spend one or more days a week in the QuTech lab in Delft, collaborating closely with the experimentalists on the development of (building blocks for) a quantum computer.
Another line of research within this theme addresses the macroscopic limit of quantum mechanics: how large can an object be and still preserve an entangled state? For that study, we have developed opto-mechanical samples with vibration-isolated cryogenics that allow us to perform measurements on the quantum properties of the system in the regime of large masses. This development has also enabled the design and study of Casimir forces with ultra-high accuracy. Other approaches towards quantum information science strongly rely on the quantum nature of light, which is the central theme of the quantum optics sections at Leiden.