Recent experimental and theoretical research on spin qubits in quantum dots have clearly demonstrated that spins have long coherence times and can be reliably controlled. Electron spin two-qubit gates can be performed using the strong exchange interaction between dots, which however is short-ranged. How to achieve long-range quantum communication for spin qubits thus remains a significant open problem in the scale-up of spin qubit architectures. One proposed approach involves the transportation of the electrons themselves, which is attractive because of its conceptual simplicity and its similarity to the conventional charge-coupled devices.

Here I discuss our studies of electron spin decoherence when the quantum dot is in motion. Specifically, we find that the motion induced spin decoherence is a pure longitudinal relaxation channel, whose rate depends on the disorder in the substrate, the strength of the magnetic field, and the speed of the quantum dot motion [1, 2]. In the case of electron-phonon interaction induced spin relaxation, we find a range of interesting phenomena originating from the Doppler shift as we vary the quantum dot speed from the subsonic regime to the supersonic regime, including Doppler shift in emitted phonons, spin relaxation boom in analogy to sonic boom, and Cherenkov radiation of phonons [2].

We thank financial support by US ARO and NSF PIF.

References : [1] P. Huang and X. Hu, Phys. Rev. B 88, 075301 (2013).

[2] X. Zhao, P. Huang, and X. Hu, Scientific Reports 6, 23169 (2016).

Contact : Xuedong Hu