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Monday, August 11 • 11:30 - 12:45
Quantum Information I

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Invited: Sven Rogge
Addressing Single Dopant Atoms in a Semiconductor Vacuum

Dopant atoms in semiconductor nano devices have recently received attention due to the variability problems in CMOS and the new opportunities for quantum electronics. The latter is based on the fact that dopants act like hydrogen atoms in a semiconductor vacuum with long coherence times and are compatible with VLSI fabrication techniques. Controlled access to single dopants has been achieved in multiple labs and recently control over the electron and nuclear spin has been demonstrated. Optical control of single qubits is very attractive since it allows for high spectral resolution, is non-local, and allows for long distance coupling but was not available in silicon. Here, we present optical addressing and electrical detection of individual erbium dopants with exceptionally narrow line width. The hyperfine coupling is clearly resolved which paves the way to single shot readout of the nuclear spin. This hybrid approach is a first step towards an optical interface to dopants in silicon. Furthermore, spatially resolved single electron tunnelling experiments will be discussed that reveal the spectrum and wavefunction of single dopants and dopant molecules. Dopants studied down to 5 nm below a Si-vacuum interface reveal a peculiar nature of the semiconductor vacuum which is the spatially resolved valley quantum interference of a donor in silicon.

Invited: Mike L. W. Thewalt
Highly Enriched 28Si – A 'Semiconductor Vacuum' Host for Spin Qubits

Enriched 28Si is a prime candidate for semiconductor-based quantum information research, since the absence of nuclear spin leads to very long coherence times for impurity electron or nuclear spins. It also has another unique property - the almost complete elimination of inhomogeneous broadening for a wide variety of optical transitions, leading to improvements in spectral resolution of over an order of magnitude, and to linewidths which are almost lifetime-limited. Since the first observation of this effect in 2001 [1], there have been a number of new discoveries and applications which I will review. Among the most important is the ability to resolve donor hyperfine splittings in donor bound exciton absorption spectra, providing an optical means of manipulating and reading out donor electron and nuclear spins. These new optical methods have allowed NMR measurements on highly enriched 28Si very lightly doped with 31P, resulting in the observation of record nuclear qubit coherence times of 180 s for the neutral 31P donor at 1.3 K [2]. While neutral donors are inherently low temperature systems, the addition of optical charge control allowed us to observe a room temperature coherence time for the nuclear spin of ionized 31P donors of 39 minutes, orders of magnitude longer than the coherence time of any other solid state qubit [3].

[1] D. Karaskaij et al., Phys. Rev. Lett. 86, 6010 (2001).
[2] M. Steger et al., Science 336, 1280 (2012).
[3] K. Saeedi et al., Science 342, 830 (2013). 

Oral: Juha Muhonen
Single-Spin Quantum Coherence Beyond 30 Seconds in Silicon Nanostructure
Co-authors: Juan Pablo Dehollain, Arne Laucht, Fay Hudson, Takeharu Sekiguchi, Kohei Itoh, David Jamieson, Jeffrey McCallum, Andrew Dzurak, Andrea Morello 

Session Chairs

Franco Nori

Chief Scientist & Group Director & Professor, RIKEN & University of Michigan
Professor Franco Nori’s research is in theoretical condensed matter physics and quantum information processing. He has also done research in computational physics, transport phenomena (e.g., of vortices or electrons), energy conversion and solar energy, as well as the dynamics of complex systems. His research work is interdisciplinary and also explores the interface between atomic physics, quantum optics, nano-science, and computing. His... Read More →


Sven Rogge

Professor, University of New South Wales
After completing his undergraduate studies at the Universität Karlsruhe in Germany, Sven moved to Stanford University (USA) joining the research group of Douglas D. Osheroff and in 1997 was awarded his PhD in physics. As a postdoctoral researcher at Delft University of Technology (Netherlands), his research focused on atomic-scale electronics with the twofold aim of realising quantum electronics in silicon and establishing atomistic-device... Read More →

Mike L. W. Thewalt

Professor, Simon Fraser University
Michael L. W. Thewalt is a Canadian physicist. He received his BSc from McMaster University in 1972. His MSc and PhD were from the University of British Columbia in the mid-1970s. He teaches at Simon Fraser University and is known for researching semiconductors, especially isotopically enriched silicon.

Monday August 11, 2014 11:30 - 12:45
Room 18CD

Attendees (27)