recent research

Continuous-variable qubit states

Please have a go with my cv qubit space flight simulator! It is science, it is fun - what can you lose?

Using a squeezed vacuum source and an advanced photon subtraction technique, we succeeded in generating a large range of different superpositions of squeezed vacuum and squeezed single-photon states. These states can be interpreted as qubits with continuous-variable basis states.

The following animation illustrates this qubit space as a Bloch sphere. Each experimentally obtained state is represented by its Wigner function at the location on the Bloch sphere corresponding to its superposition parameters.

Watch the movie on Vimeo.

I have also developed an interactive applet that allows you to move around in the qubit space and investigate each state in detail. Go to the cv qubit applet here.

academic history

Full CV for download
Bachelor studies in physics and mathematics at University of Copenhagen.
Master studies in physics. My thesis work was carried out in the Quantop group at the Niels Bohr Institute, University of Copenhagen.
PhD studies in experimental quantum optics at Quantop under the supervision of Prof. Eugene Polzik.
March–May 2006
Research exchange student in the Furusawa laboratory at the University of Tokyo.
October 2008–September 2011
Limited term researcher (post doc) in the Quantum ICT Group at NICT (National Institute of Information and Communications Technology) in Koganei, Tokyo.
September 2011–
Post doc in the Quantum Information Group at DTU (Technical University of Denmark) in Lyngby, Denmark.

My theses for download

Master thesis
Nonclassical light source for quantum networks [ pdf, 3.4 MB ]
PhD thesis
Generation of single photons and Schrödinger kitten states of light
[ DOI:10.6074/m9.figshare.1328405 | pdf, 11.2 MB ]


Journal articles

In conference proceedings, etc.

  • Continuous variable qubit state engineering
    J. S. Neergaard-Nielsen, M. Takeuchi, K. Wakui, H. Takahashi, K. Hayasaka, M. Takeoka & M. Sasaki
  • Quantum interface between light and atomic ensembles
    H. Krauter, J. Sherson, K. Jensen, T. Fernholz, D. Oblak, P. J. Windpassinger, N. Kjærgaard, J. Neergaard-Nielsen, B. Melholt-Nielsen, A. Hilliard, C. Olausson, J.H. Müller & E. S. Polzik
    Laser Spectroscopy. Proceedings of the XVIII ICOLS 2007, Eds. L. Hollberg, J. Bergquist, M. Kasevich, World Scientific (2008)
  • Narrow bandwidth optical Schrödinger kitten states and single photons
    Jonas S. Neergaard-Nielsen, Bo Melholt Nielsen, Christian Hettich, Hiroki Takahashi, Arnt Inge Vistnes & Eugene S. Polzik
    Proceedings of the 8th International Conference on QCMC 2006, Eds. O. Hirota, J. H. Shapiro, and M. Sasaki (2007)

Other articles

© Jonas Schou Neergaard-Nielsen, 2008-13