Xuedong Hu: Quantum Communication for Spin Qubits

Abstract:

Recent experimental and theoretical research on spin qubits in quantum dots
have clearly demonstrated that spins have long coherence time and can be reliably
controlled. Electron spin two-qubit gates can be performed using the strong exchange
interaction, 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. In this talk I will give an overview of the various
approaches to achieve spin information transfer, such as those based on spin-photon
coupling, or based on a spin bus made from a spin chain. I will then focus on a
particular approach that involves the transportation of the electrons themselves,
which is attractive because of its conceptual simplicity and its similarity to the
conventional charge-coupled devices. Indeed, recently several experimental groups have
shown how an electron can be transported over a distance of several microns between two
quantum dots by a surface acoustic wave (SAW) in GaAs. I will discuss our recent work
on the physics 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. Our results not only show how severe a problem this decoherence
could be, but also clearly indicate how to reduce the decoherence effects of electron
motion.

We thank support by US ARO, DARPA QuEST, and NSF PIF.