title: Magnetically tunable singlet-triplet spin qubit in a four-electron InGaAs coupled quantum dot.
abstract: A pair of self-assembled InGaAs quantum dots filled with two electrons can act as a singlet-triplet spin qubit that is robust against nuclear spin fluctuations as well as charge noise. This results in a T2* coherence time two orders of magnitude longer than that of a single electron, provided the qubit is operated at a particular "sweet spot" in gate voltage. However, at this fixed operating point the ground-state splitting can no longer be tuned into resonance with e.g. another qubit, limiting the options for coupling multiple qubits. Here, we propose using a four-electron coupled quantum dot to implement a singlet-triplet qubit that features a magnetically tunable level splitting. As a first step towards full experimental realization of this qubit design, we use optical spectroscopy to demonstrate the tunability of the four-electron singlet-triplet splitting in a moderate magnetic field.
authors.affiliation: Institute for Quantum Electronics, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: K M
authors.initials: KM
authors.lastname: Weiss
authors.forename: J
authors.initials: J
authors.lastname: Miguel-Sanchez
authors.forename: J M
authors.initials: JM
authors.lastname: Elzerman