Quantum control in silicon using coherent THz pulses

Stephen A. Lynch; P. Thornton Greenland; Alexander F. G. van der Meer; Benedict N. Murdin; Carl R. Pidgeon; Britta Redlich; Nguyen Q. Vinh; Gabriel Aeppli

doi:10.1117/12.928571

15 October 2012 Quantum control in silicon using coherent THz pulses

Stephen A. Lynch, P. Thornton Greenland, Alexander F. G. van der Meer, Benedict N. Murdin, Carl R. Pidgeon, Britta Redlich, Nguyen Q. Vinh, Gabriel Aeppli

Author Affiliations +

Proceedings Volume 8496, Terahertz Emitters, Receivers, and Applications III; 84960O (2012) https://doi.org/10.1117/12.928571
Event: SPIE Optical Engineering + Applications, 2012, San Diego, California, United States

Abstract

It has long been known that shallow donors such as phosphorous and the other group-V elements, have a hydrogen-like optical spectrum. The main difference is that while the spectrum of atomic hydrogen lies in the visible band, the spectrum of shallow donors in silicon is downshifted to the THz frequency band. This is a direct consequence of the reduced Coulomb attraction seen by the loosely bound electron because the core electrons shield the positive donor atom nucleus, and because the electron is now moving in a dielectric material. While spectroscopy has already revealed much about the energy level structure, very little was known about the temporal dynamics of the system until now. We have used THz pulses from the FELIX free electron laser to probe these hydrogen-like levels. By exploiting the well-known pump-probe technique we have measured the characteristic lifetimes of the excited Rydberg states and found them to be of the order 200 ps. Then, by making subtle changes to the geometry of the pump-probe experimental setup we demonstrate the existence of a THz photon echo. The photon echo is a purely quantum phenomenon with no classical analogue, and it allows us to study the quantum state of the donor electron. We then show, using the photon echo, that it is possible to create a coherent superposition of the ground and excited state of the donor. Measuring the photon echo is important because it can also be used to measure a second important characteristic lifetime of the silicon-donor system, the phase decoherence time.

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Stephen A. Lynch, P. Thornton Greenland, Alexander F. G. van der Meer, Benedict N. Murdin, Carl R. Pidgeon, Britta Redlich, Nguyen Q. Vinh, and Gabriel Aeppli "Quantum control in silicon using coherent THz pulses", Proc. SPIE 8496, Terahertz Emitters, Receivers, and Applications III, 84960O (15 October 2012); https://doi.org/10.1117/12.928571

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