Atomic silicon circuitry
Our main building block is the silicon dangling bond on a H-terminated silicon surface, which we have shown acts as a quantum dot. Precise assemblies of such dots can be created to form artificial molecules. Such ensembles can have custom optical properties, can serve as circuit elements for quantum-dot cellular automata, and, we suspect, can play a role in quantum computing.
Our work has pushed the boundaries of atom-scale fabrication, imaging techniques, and dynamic charge sensing of single surface atoms and of single dopants. See Publications for all of our recent work.
Because the atomic silicon quantum dot (ASiQD) is so small - perhaps the ultimate small dot - it has very widely spaced electronic energy levels. This has multiple important ramifications. The Quantum Dot Cellular Automata scheme due to Lent, Porod and coworkers, for example, is now set to flourish. While the QCA architecture has been highly developed theoretically and proven experimentally, it has until now languished because the relatively large size, and commensurately small energy level spacing of available dots required extreme cryogenic conditions. Our patented ASiQDs now allow room temperature operation, while simultaneously eliminating practical issues related to clocking and wiring. Spin-off company Quantum Silicon Incorporated, QSi, is tackling the challenges of interfacing the new atom-sized circuitry to conventional CMOS and to make first working prototypes.
Within the QCA scheme, the binary states “1” and “0” are encoded in the position of electric charge. Variants exist but most commonly the basic cell consists of a rectangular quantum dot ensemble occupied by 2 electrons. Multiple cells couple and naturally mimic the electron configuration of nearest-neighbour cells. In general, cell-cell interactions must be described quantum mechanically but to a good approximation
they are described simply by electrostatic interactions. Electrons freely tunnel among the quantum dots in a cell, while electron tunneling between cells does not occur. Within a cell, two classically equivalent states exist, each with electrons placed on a diagonal.
Design and test atomic circuits now using SiQAD
See Bob's TED Talk on Atom Scale Manufacturing here
a) Scanning tunneling microscope (STM) images of a rewritable 8-bit memory constructed from dangling bonds (DBs) and b) an STM image of an expanded 192-bit memory, storing 24 simplified notes (converted into binary) of the popular Mario video game theme song.
Interested in visiting, collaborating, or working with us?
drop us a line
Robert Wolkow - Group Supervisor
Department of Physics - Condensed Matter
CCIS 3-182 11455 Saskatchewan Drive NW
Edmonton, AB T6G 2R3
Office hours are by appointment only
The University of Alberta is committed to cultivating an institutional culture that values, supports, and promotes equity, human rights, respect, and accountability among faculty, staff, and students.
Currently, no consideration will be given to candidates without expert-level ultra high vacuum scanning tunneling microscopy skills.
Salaries are currently about $50,000. Some travel assistance is available. Medical and Dental coverage is provided.
The research group includes people with backgrounds in physics, chemical physics, engineering and chemistry. In our group we enjoy a pleasant and dynamic atmosphere where one can become immersed in exciting science.
Our group’s laboratories are extremely well equipped (See Our Facilities).
Edmonton, Alberta is a wonderful place to live offering the advantages of a big city; ballet (truly excellent and my favourite), opera, symphony, extensive theatre, galleries - while still having a safe, small town feeling. A wide range of popular outdoor activities are also available ranging from bicycling to camping and kayaking, and skiing. The spectacular Rocky Mountains are about 3.5 hours away by car.
Appointments ordinarily run for two years and may be extended for a third year. Applicants must have a strong mechanical aptitude and hands-on experience with ultra high vacuum techniques. A PhD in physics or chemistry (chemical physics oriented) is required.
Graduate physics students can study with me by becoming a graduate student at the University of Alberta Physics Department where I am a professor. A co-supervised theory student position is available too, in cooperation with Professor Hong Guo at McGill University (where I am an adjunct prof.) Co-supervised chemistry graduate students too are welcome.
Summer students can also join us. Interested students should make contact through their university's undergraduate summer job placement services or by sending an email to me. Summer students should have demonstrable mechanical aptitude (could you fix a flat tire on your bike when you were a kid?, have you built an electronic circuit?, can you program?). Give anecdotes to describe such experience, send me an unofficial transcript, send a resume too please.