Coherent control of Rydberg states in silicon

London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1H 0AH, UK.
Nature (Impact Factor: 41.46). 06/2010; 465(7301):1057-61. DOI: 10.1038/nature09112
Source: PubMed


Laser cooling and electromagnetic traps have led to a revolution in atomic physics, yielding dramatic discoveries ranging from Bose-Einstein condensation to the quantum control of single atoms. Of particular interest, because they can be used in the quantum control of one atom by another, are excited Rydberg states, where wavefunctions are expanded from their ground-state extents of less than 0.1 nm to several nanometres and even beyond; this allows atoms far enough apart to be non-interacting in their ground states to strongly interact in their excited states. For eventual application of such states, a solid-state implementation is very desirable. Here we demonstrate the coherent control of impurity wavefunctions in the most ubiquitous donor in a semiconductor, namely phosphorus-doped silicon. In our experiments, we use a free-electron laser to stimulate and observe photon echoes, the orbital analogue of the Hahn spin echo, and Rabi oscillations familiar from magnetic resonance spectroscopy. As well as extending atomic physicists' explorations of quantum phenomena to the solid state, our work adds coherent terahertz radiation, as a particularly precise regulator of orbitals in solids, to the list of controls, such as pressure and chemical composition, already familiar to materials scientists.

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    • "A few experimental techniques are available to probe the silicon phononiton system (low temperature, T ∼ 1 K, and low phonon numbers are assumed). First, freeelectron lasers have been used to probe the 1s − 2p transitions in silicon [38]. Observation of the vacuum Rabi splitting by measurement of the absorption spectrum of the allowed optically probed transition 1s(T 2 ) → 2p 0 (∼ 30 meV) using weak optical excitation of the single micro-pillar cavity, arrays, or delta-doped 1D structures would provide confirmation of phononiton physics. "
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    ABSTRACT: A quantum mechanical superposition of a long-lived, localized phonon and a matter excitation is described. We identify a realization in strained silicon: a low-lying donor transition (P or Li) driven solely by acoustic phonons at wavelengths where high-Q phonon cavities can be built. This phonon-matter resonance is shown to enter the strongly coupled regime where the "vacuum" Rabi frequency exceeds the spontaneous phonon emission into non-cavity modes, phonon leakage from the cavity, and phonon anharmonicity and scattering. We introduce a micropillar distributed Bragg reflector Si/Ge cavity, where Q=10^5-10^6 and mode volumes V<=25*lambda^3 are reachable. These results indicate that single or many-body devices based on these systems are experimentally realizable.
    • "The experiments described were performed using the FELIX free electron laser at the FOM institute at Nieuwegein in the Netherlands. A full description of the experiment can be found in our recently published paper [8]. The main cogent points, however, are summarized in this conference abstract. "
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    ABSTRACT: We demonstrate THz photon echoes from silicon doped with phosphorus donors. We provide experimental evidence showing that the echo emerges at the predicted angle and that it arrives at our detector at the predicted time. We use this to demonstrate coherent control of the silicon donor states.
    Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010 35th International Conference on; 10/2010
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    ABSTRACT: We demonstrate the first observation of a THz photon echo. We exploit the photon echo as an experimental tool to investigate the quantum coherence properties of excited donor Rydberg states of phosphorus in silicon.
    Group IV Photonics (GFP), 2010 7th IEEE International Conference on; 01/2010
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