Integriert optische Quantensysteme aus Fluor-Donator Qubits

• Applicant: Professor Dr. Klaus Lischka
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2012 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 201128336

• Final Report Year: 2015

Final Report Abstract

Although some time will go by until the replacement of classic computers by a quantum computer strong efforts are made to investigate their basic components. The motivation to realize a solidstate implementation of quantum devices triggered the idea to make use of impurity atoms in a semiconductor as one option for single photon sources and qubits. In this context, fluorine was proposed as a suitable donor impurity in ZnSe, since it provides properties which are specific for quantum information applications. Within this project sophisticated nano-structuring techniques were developed to isolate single fluorine donors in ZnMgSe/ZnSe quantum structures and a photon source which delivers single photons on demand was realized with fluorine doped ZnSe. The potential of such sources was demonstrated through the entanglement of indistinguishable photons of two independent devices. The serious problem of any quantum device however is the interaction of the quantum states with the “environment”, which can lead to the loss of the quantum information. A measure of the stability of the quantum system is the coherence time. The longer this time, the more stable is the qubit. For the fluorine donor in ZnSe coherence times exceeding 30 ns were measured and confirmed substantial robustness of the electron spin states of the ensemble of ZnSe:F qubits even in the presence of non-zero nuclear spins in the host crystal. Furthermore, the magneto-optical properties of single qubits were studied and revealed the presence of a threelevel system that can be used as an interface between fluorine qubits and the emitted single photons. The performance of this interface was demonstrated by optical initialization and readout of the quantum state of the fluorine qubit. Due to the fact that the quantum properties of atoms are well understood our experimental research confirmed the theoretical expectations in most cases.

Publications

• Entangling single photons from independently tuned semiconductor nanostructures, Nano Letters 12, 4611 (2012)
  K. Sanaka, A. Pawlis, T.D. Ladd, D. J. Sleiter, K. Lischka, Y. Yamamoto
  
• Optical properties of fluorine implanted ZnMgSe/ZnSe quantum-well nanostructures, Proc. of SPIE 8272, 827213 (2012)
  Y. M. Kim, D. Sleiter, K. Sanaka, Y. Yamamoto, J. Meijer, K. Lischka, A. Pawlis
  
• Spin dephasing of fluorine-bound electrons in ZnSe,Phys. Rev. B (Rapid Comm.) 85, 121303(R) (2012)
  A. Greilich, A. Pawlis, F. Liu, O.A. Yugov, D.R. Yakovlev, K. Lischka, Y. Yamamoto, M. Bayer
  
• Optical pumping of a single electron spin bound to a Fluorine donor in ZnSe, Nano Letters 13, 116 (2013)
  D. J. Sleiter, K. Sanaka, M. Kim, K. Lischka, A. Pawlis, Y. Yamamoto
  
• All-optical NMR in semiconductors provided by resonant cooling of nuclear spins interacting with electrons in the resonant spin amplification regime, Phys. Rev. B 90, 085311 (2014)
  E.A. Zhukov, A. Greilich, D.R. Yakovlev, K.V. Kavokin, I.A. Yugova, O.A. Yugov, D. Suter, G. Karczewski, T. Wojtowicz, J. Kossut, V.V. Petrov, Yu.K. Dolgikh, A. Pawlis, M. Bayer
  
• Optically controlled initialization and read-out of an electron spin bound to a fluorine donor in ZnSe, Curr. Appl. Phys. 14, 1234 (2014)
  Y.M. Kim, D. Sleiter, K. Sanaka, D. Reuter, K. Lischka, Y. Yamamoto, A. Pawlis
  
• Extending the spectral range of CdSe/ZnSe quantum wells by strain engineering, Phys. Rev. B 91, 035409 (2015)
  A. Finke, M. Ruth, S. Scholz, A. Ludwig, A.D. Wieck, D. Reuter, A. Pawlis