Quantum Technologies
Research activities
Hybrid quantum technologies with atomscale defects
Semiconductor technology lies at the heart of modern industry. Its vast importance is given by the versatility of semiconductors as information processor, sensors and mechanical devices. Quantum physics offers tools for greatly enhanced performance in all these applications. We have recently found that spin centers in commercial silicon carbide (SiC) wafers, that are used for device fabrication, possess very favorable quantum properties [1] even at room temperature [2], pushing this field towards practical applications. We can precisely engineer these spin centers [3] down to single defect level [4] and coherently manipulate their quantum states [5]. Our goals:

Quantum semiconductor integrated circuits with spin qubits fabricated at the Ion Beam Center (IBC) using Nanofabrication Facility. This concept allows to go far beyond the diffraction limit and create an array of qubits with individual addressability on a single chip. Particularly, they can be used for quantum sensing with unprecedented accuracy.

Controllable creation of single spin color centers in SiC and Si at the Ion Beam Center (IBC) and integration into highquality photonic cavities to achieve an efficient spinphoton entanglement. This is an important step towards implementation of quantum repeaters and networks with eavesdropping detection.

Creation of dense and highlycoherent spin defect ensembles using the Electron Accelerator ELBE and integration into highquality microwave cavities to implement a roomtemperature semiconductor maser. Such a quantum amplifier can be used for compact satellite receivers, highly precise remote sensing and chipscale secondary frequency standards.
Quantum metrology with topological materials
There is a continuously growing interest to topological quantum states, particularly to 3D topological insulators (TIs) because of attractively new and unusual physics they demonstrate. One of the most soughtafter phenomena in topological quantum matter is the socalled topological magnetoelectric (TME) effect. It is expected due to axion electrodynamics of TIs, caused by additional terms in the Maxwell’s equations that couple an electric field to a magnetization and a magnetic field to a polarization of the matter. The direct manifestation of the TME effect is the universal Faraday rotation angle of the linearly polarized THz radiation quantized in terms of the fine structure constant α, which we confirmed in our experiments [6]. We aim to address fundamental questions using the freeelectron lasers FELBE and the Dresden High Magnetic Field Laboratory (HLD):

How precisely is the observed Faraday rotation equal to the fine structure constant? It would be very exciting to use topological phenomena in solids, namely the magnetic flux quantum from the Josephson effect, the conductivity quantum from the quantum Hall effect and now the quantized Faraday rotation from the TME effect, for a metrological definition of the three basic physical constants e, h and c.

Topological insulators mimic axion particles (dark matter). Can we investigate “baby universe” in tabletop experiments using timeresoved/timedomain THz spectroscopy [7]?
Related Publications
[1] Resonant addressing and manipulation of silicon vacancy qubits in silicon carbide
D. Riedel, F. Fuchs, H. Kraus, S. Väth, A. Sperlich, V. Dyakonov, A. A. Soltamova, P. G. Baranov, V. A. Ilyin, G. V. Astakhov
Phys. Rev. Lett. 109, 226402 (2012)  arXiv:1210.0505
[2] Room temperature quantum microwave emitters based on spin defects in silicon carbide
H. Kraus, V. A. Soltamov, D. Riedel, S. Väth, F. Fuchs, A. Sperlich, P. G. Baranov, V. Dyakonov G. V. Astakhov
Nat. Phys. 10, 157 (2014)
[3] Threedimensional proton beam writing of optically active coherent vacancy spins in silicon carbide
H. Kraus, D. Simin, C. Kasper, Y. Suda, S. Kawabata, W. Kada, T. Honda, Y. Hijikata, T. Ohshima, V. Dyakonov, G. V. Astakhov
Nano Lett. 17, 2865 (2017)
[4] Engineering nearinfrared singlephoton emitters with optically active spins in ultrapure silicon carbide
F. Fuchs, B. Stender, D. Simin, M. Trupke, J. Pflaum, V. Dyakonov, G. V. Astakhov
Nat. Commun. 6, 7578 (2015)  arXiv:1407.7065
[5] Locking of electron spin coherence above 20 ms in natural silicon carbide
D. Simin, H. Kraus, A. Sperlich, T. Ohshima, G. V. Astakhov, V. Dyakonov
Phys. Rev. B 95, 161201(R) (2017)  arXiv:1602.05775
[6] Observation of the universal magnetoelectric effect in a 3D topological insulator
V. Dziom, A. Shuvaev, A. Pimenov, G. V. Astakhov, C. Ames, K. Bendias, J. Böttcher, G. Tkachov, E. M. Hankiewicz, C. Brüne, H. Buhmann, L. W. Molenkamp
Nat. Commun. 8, 15197 (2017)  arXiv:1603.05482
[7] Surface state charge dynamics of a highmobility three dimensional topological insulator
J. Hancock, J. L. M. van Mechelen, A. B. Kuzmenko, D. van der Marel, C. Brüne, E. G. Novik, G. V. Astakhov, H. Buhmann, L. W. Molenkamp
Phys. Rev. Lett. 107, 136803 (2011)