Hy-Q Seminar: Sjaak van Diepen

Magnetic behaviour, caused by the underlying ordering of spins, can take intricate forms when interactions result in quantum-mechanical correlations. Analog quantum simulators, which behave like the system of interest, can possibly provide insights into such behaviour. Gate-defined quantum dots, in addition to being of interest for quantum computation, have po­tential for quantum simulation of magnetism. We operate a linear array of four quantum dots in a GaAs/AlGaAs heterostructure. The quantum dots are tuned to the half-filling regime, where each site is occupied with a single electron. In this regime only the spin degree of freedom remains, and a Heisenberg spin chain can be formed. We extract various properties of the spin chain based on pairwise spin measurements and correlations therein. First, we study the energy spectrum as a function of gate voltages and an external magnetic field. Then, we quantitatively characterize the ground state for a homogeneously interacting spin chain. Last, we observe col­lective coherent oscillations of the four-spin system in subspaces with different magnetization. Building on the demonstrated control and characterization techniques, interesting next steps are to simulate magnetism with a larger number of spins and in different lattice configurations.