Single Atoms for Quantum Computers

STM-image showing the atomic level detail of the electron wave function of a phosphorus atom in a silicon chip (Source: CQC2T)

STM-image showing the atomic level detail of the electron wave function of a phosphorus atom in a silicon chip (Source: CQC2T)

Researchers from the Centre for Quantum Compu­tation and Communi­cation Techno­logy have been able to identify the exact location of a single atom in a silicon crystal. This is an important step for building a silicon-based quantum computer.

Individual phos­phorus atoms placed in a silicon crystal have great potential as quantum bits, or qubits – the core com­ponents of large-scale quantum processors. Being able to pinpoint the position of a qubit is critical for the design of accurate quantum logic ope­rations, where calculations will be carried out between qubits of infor­mation.

The world-first approach for locating the introduced, or donor, atoms in the silicon crystal lattice involved a combination of theory and experimental images. “We were able to obtain high-reso­lution images of individual phos­phorus and arsenic donors below the silicon surface,” says Juanita Bocquel. “Close collaboration with theory success­fully pin­pointed donor atoms in the silicon lattice at positions that are relevant for quantum compu­tation.”

Main investigator Muhammad Usman says: “The images showed a dazzling array of symmetries that seemed to defy expla­nation, but when the environ­ment of the quantum state was explicitly taken into account in the theore­tical treatment, suddenly the images made perfect sense.”

“The STM images have remarkable detail, showing the tendrils of the donor’s electron wave function protruding from the silicon surface inter­acting directly with the scanning STM tip. The final images are therefore highly sensi­tive to the absolute location of the donor atom”, says group leader Lloyd Hollen­berg.

Sven Rogge, who heads the low tempe­rature STM imaging laboratory, believes that the ability to exactly pinpoint the quantum bit is critical in under­standing not only how these objects will be used to perform quantum logic gates in a quantum computer, but also how such donor atoms could affect other ultra-scaled nano­electronic devices. (Source: Univ. Melbourne)

Reference: M. Usman et al.: Spatial metrology of dopants in silicon with exact lattice site precision, Nat. Nano. online 06 June 2016, DOI: 10.1038/nnano.2016.83

Link: Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Australia

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