Theoretical Nanophysics

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From flying qubits with ballistic electrons towards quantum optics with flying electrons

Christopher Bäuerle (CNRS, Grenoble)

27.01.2012 at 10:15 

Coherent manipulation of qubits, creation of quantum entanglement, and coherent transfer of quantum information are the core of quantum information technology. Employed with confined quantum states, a solid-state system is considered to have advantages on qubit manipulation and scalability. However, coherent transfer of quantum information over a long distance in a solid-state system is still a big challenge.

In the first part of my talk, I will report on the realization of a solid-state flying qubit, employing an Aharonov-Bohm (AB) ring connected to two-channel wires with tuneable tunnel coupling between the channels. The flying qubit state is defined by the presence of a travelling electron in either channel of the wire. Quantum information in form of a flying qubit state is transferred over 6.5 μm distance within 40 ps. Qubit operations were achieved with static gate voltages but the high speed of electrons makes them traverse quantum gates at a frequency of the order of 100 GHz, which opens a new avenue for fast and coherent control of solid-state qubits.

In the second part of the talk I will show how such a system could be used to realize quantum optics experiments with single flying electrons. We demonstrate the first step towards this goal, namely the on demand single electron transfer [2]. In particular we will show that a single flying electron can be sent on-demand from one quantum dot to another, several micrometer distant quantum dot with very high fidelity. The transport of the single electron is achieved by means of a sound wave, which acts as a moving dot potential and which transports the single electron protected from the environment [2,3].

Combining both schemes, this technology is opening an exciting platform for the transfer of quantum optics experiments to on chip solid-state devices

[1] M. Yamamoto, S. Takada, C. Bäuerle, K. Watanabe, A. D. Wieck & S. Tarucha, submitted

[2] S. Hermelin, S. Takada, M. Yamamoto, S. Tarucha, A. D. Wieck, L. Saminadayar,
     C. Bäuerle and T. Meunier, Nature, 477, 7365 (20011)

[3] R. Mc Nail et al., Nature, 477, 7369 (20011)


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