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Coherent long-range transport of entangled electron spins

Abstract : Quantum computing is a field of growing interest, especially in Grenoble with an exceptional concentration of both research and industrials groups implicated in this field. The global aim is to develop a new kind of nano-processors, based on quantum properties. Its building brick is a two-level quantum system, in our case the spin of electrons trapped in a quantum dot.In this quest for a large-scale architecture, networked quantum computers offer a natural path towards scalability. Indeed, separating the computational task among quantum core units interconnected via a coherent quantum mediator would greatly simplify the addressability challenges. These quantum links should be able to coherently couple arbitrary nodes on fast timescales, in order to share entanglement across the whole quantum circuit. In semiconductor quantum circuits, nearest neighbor entanglement has already been demonstrated, and several schemes exist to realize long-range coupling. Among them, a possible implementation of this quantum mediator would be to prepare an entangled state and shuttle individual electron spins across the structure, provided that this transport preserves the entanglement.In this work, we demonstrate the fast and coherent transport of electron spin qubits across a 6.5 μm long channel, in a GaAs/AlGaAs laterally defined nanostructure. Using the moving potential induced by a propagating surface acoustic wave, we send sequentially two electron spins initially prepared in a spin singlet state. During its displacement, each spin experiences a coherent rotation due to spin-orbit interaction, over timescales shorter than any decoherence process. By varying the electron separation time and the external magnetic field, we observe quantum interferences which prove the coherent nature of both the initial spin state and the transfer procedure.We show that this experiment is analogous to a Bell measurement, allowing us to quantify the entanglement between the two electron spins when they are separated, and proving this fast and long-range qubit displacement is an efficient procedure to share entanglement across future large-scale structures.
Keywords : Spin Entanglement Qubit
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Submitted on : Thursday, September 24, 2020 - 9:34:08 AM
Last modification on : Friday, September 25, 2020 - 3:28:06 AM

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  • HAL Id : tel-02947700, version 1

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Baptiste Jadot. Coherent long-range transport of entangled electron spins. Materials Science [cond-mat.mtrl-sci]. Université Grenoble Alpes [2020-..], 2020. English. ⟨NNT : 2020GRALY007⟩. ⟨tel-02947700⟩

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