Single electrons trapped by individual donors in semiconductors at low temperatures have very good homogeneity when compared to other semiconductor systems, such as quantum dots. When excited to the donor-bound exciton state, these donors will emit very homogeneous single photons with a wavelength of 400nm.
In this project, individual donors are tested as single photon sources. g(2)(0) data from single sources proves that they are indeed single photon sources, and a Hong-Ou-Mandel dip observed when interefering photons from two independent donors shows that they are indistinguishable. Single photon sources are necessary components of most quantum repeater designs, and are applicable to many quantum information technologies.
Figure 1. Comparison of emission from two donors (device A and device B). Plot shows photoluminescence spectra, left subplots show the relative emission time after optical excitation, and right subplots show g(2)(τ) for the two donors.
Figure 2. Hong-Ou-Mandel dip observed in the interference between single photons from two separate donors. Histogram of delay between the arrival of two photons (a) with a balanced interferometer and (b) with a 0.2 ns delay. (c) Two photon coincidence as a function of interferometric path delay.
Kaoru Sanaka, Alexander Pawlis, Thaddeus D. Ladd, Klaus Lischka, and Yoshihisa Yamamoto, "Indistinguishable Photons from Independent Semiconductor Nanostructures", Phys. Rev. Lett. 103, 053601 (2009). [http://dx.doi.org/10.1103/PhysRevLett.103.053601]
Kristiaan De Greve
Dr. Susan Clark
Dr. Kaoru Sanaka
Prof. Yoshihisa Yamamoto