Donors as qubits
In semiconductors, several types of artificial atoms are actively being investigated for their application in quantum information processing. Among these are donor states such as those of phosphorus donors in silicon. Phosphorus, an atom from group V of the table of elements, has one electron more than Silicon, a group-IV atom. At low temperatures, this electron stays bound to the P donor.
Several different ways have been proposed in which either the spin of this electron or the spin of the 31P nucleus can be used as a quantum bit or qubit. Our research group investigates methods to read out the spin state of these qubits using pulsed magnetic resonance techniques. As spin-to-charge conversion, which is required to detect spin states via electrical measurements, we use the spin-dependent transfer of the donor electron to a paramagnetic state which occurs naturally at the Si/SiO2 interface.
We have recently demonstrated that Rabi oscillations of the donor electron spin can be monitored via photoconductivity measurements under pulsed microwave excitation. Via so-called echo tomography, we have furthermore shown that spin echos also can be observed in pulsed electrically detected magnetic resonance (pEDMR). This technique opens the way to apply further, more complicated pulsed magnetic resonance schemes which should allow to measure spin-spin interactions, the effect of electric fields on the donor wavefunction and the spin state of the phosphorus nucleus.
A more introductory text into the origin of spins, their usage in modern technology, the realization of large artificial atoms in semiconductors and their application for quantum information processing can be found in chapter 10 of the WSI brochure (English version, Kapitel 10 in deutscher Sprache).
Review
- Donors for Quantum Information Processing
M.S. Brandt
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Selected publications
- Electrical detection of coherent 31P spin quantum states
A.R. Stegner, C. Boehme, H. Huebl, M. Stutzmann, K. Lips, M.S. Brandt
Nature Physics 2, 835 (2006), arXiv:quant-ph/0607178v1
Download - Phosphorus donors in highly strained silicon
H. Huebl, A.R. Stegner, M. Stutzmann, M.S. Brandt, G. Vogg, F. Bensch, E. Rauls, U. Gerstmann
Physical Review Letters 97 166402 (2006)
Download - Electrically detected magnetic resonance in ion-implanted Si:P nanostructures
D.R. McCamey, H. Huebl, M.S. Brandt, W.D. Hutchison, J.C. McCallum, R.G. Clark, A.R. Hamilton
Applied Physics Letters 89 182115 (2006)
Download - Spin echoes in the charge transport through phosphorus donors in silicon
H. Huebl, F. Hoehne, B. Grolik, A.R. Stegner, M. Stutzmann, M.S. Brandt
Physical Review Letters 100 177602 (2008)
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Collaborations
Funding
DFG via SFB 631 “Solid-State Quantum Information Processing”, Teilprojekt C3 “Fundamentals of Quantum Logic Gates in Silicon”