Manipulating and characterizing spin qubits based on donors in silicon with electromagnetic field
Single donors in semiconductors are promising candidates for spin qubits and have attracted a lot of interest in the past decades. Quantum dots defined by single donors in silicon as spin qubits are expected to have homogeneous performance as they are highly localized and the electron wave function is confined by natural Coulomb potential. Also, scanning tunneling microscopy (STM) lithography technique allows positioning donors deep into the silicon lattice with atomic precision, which makes it promising to fabricate a scalable solid-state quantum computer. The qubit information, i.e. “0” and “1”, can be encoded in the electron spins or the nuclear spins in a donor or a donor-cluster (several closely packed donors in silicon). In this work, it is demonstrated that the manipulation and readout of a qubit defined in the electron spins of donor-clusters in silicon can be realized with electron spin resonance (ESR) technique. For donor-cluster qubits fabricated with STM lithography technique, there exist configuration uncertainties, i.e. the number of donors, the number of electrons and donor locations, which lead to different quantum confinement. As a result, factors that can affect qubit performance such as binding energy, tunnel coupling, and exchange coupling can vary significantly. Hereby, a characterization technique based on the spin structure and ESR technique is developed to identify the configurations of donor-clusters and to determine the corresponding manipulation frequencies of ESR signals for single and multiple coupled qubits. Qubit operations with electrical and magnetic control are also demonstrated in a two-donor-cluster-qubit system. This work is useful for understanding and designing experimental two-qubit devices in silicon.
Klimeck, Purdue University.
Electrical engineering|Quantum physics|Condensed matter physics
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