title: Radio frequency measurements of tunnel couplings and singlet-triplet spin states in Si:P quantum dots.
abstract: Spin states of the electrons and nuclei of phosphorus donors in silicon are strong candidates for quantum information processing applications given their excellent coherence times. Designing a scalable donor-based quantum computer will require both knowledge of the relationship between device geometry and electron tunnel couplings, and a spin readout strategy that uses minimal physical space in the device. Here we use radio frequency reflectometry to measure singlet-triplet states of a few-donor Si:P double quantum dot and demonstrate that the exchange energy can be tuned by at least two orders of magnitude, from 20 μeV to 8 meV. We measure dot-lead tunnel rates by analysis of the reflected signal and show that they change from 100 MHz to 22 GHz as the number of electrons on a quantum dot is increased from 1 to 4. These techniques present an approach for characterizing, operating and engineering scalable qubit devices based on donors in silicon.
authors.affiliation: Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: M G
authors.initials: MG
authors.lastname: House
authors.affiliation: Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: B
authors.initials: B
authors.lastname: Weber
authors.affiliation: Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: S J
authors.initials: SJ
authors.lastname: Hile
authors.affiliation: Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: T F
authors.initials: TF
authors.lastname: Watson
authors.affiliation: Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: J
authors.initials: J
authors.lastname: van der Heijden
authors.affiliation: Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Rogge
authors.affiliation: Centre of Excellence for Quantum Computation and Communication Technology, School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia.
authors.forename: M Y
authors.initials: MY
authors.lastname: Simmons