Control of a GaAs “QuByte” in the single electron regime – adding dots one-by-one

Spin qubits based on semiconductor quantum dots (QDs) are promising building blocks for quantum computation. So far, research mainly focused on devices with up to four QDs. However, quantum algorithms, quantum simulations and mediators to exchange quantum information require larger and scalable systems. Though, controlled filling becomes challenging with an increasing number of QDs due to cross-capacitances and electron latching effects.
We develop a scalable technique, the ‘n+1 strategy’ where, starting from a double QD, subsequent QDs will be added one-by-one. We measure the capacitive coupling between all relevant gates and the QDs in order to create a parameter set of virtual gates. That allows individual control of chemical potentials and thus the number of electrons on each QD and furthermore the adjustment of tunnel rates.
We successfully use this technique to tune up a linear array of eight QDs ‘QuByte’ in GaAs so they are occupied by one electron each.