Long distance on-chip coupling


Principal Investigators: Hendrik Bluhm Lars Schreiber

  QuBus schematic Copyright: J. Klos

A key challenge for the scalability of quantum computer architectures based on semiconductor qubits is the realization of a coherent link between separated quantum registers on a chip. Such a link would serve two important functions. First, it enables a modular structure that allows expanding the number of qubits beyond the limits of local registers. Second, coherent links between registers create space for classical control circuits to be integrated with the qubits on-chip.

A very promising route towards realizing a coherent link is a so-called quantum bus (QuBus), a linear array of gates capable of generating a movable trapping potential, i.e. a moving quantum dot. In our group we are working on quantum busses based on both GaAs/(Al,Ga)As and Si/SiGe heterostructures. In each of these platforms, we aim at demonstrating a quantum bus that coherently transfer a single electron with an arbitrary spin between quantum dots separated by 1 to 10 microns.

Experimentally, the problem of qubit shuttling is separated into three intermediate steps: (I) Reliable charge transfer. (II) Reliable transfer of the spin projection (III) High-fidelity transfer of arbitrary spin states. To enable true networks, we will also demonstrate a QuBus that forms branches and investigate the benefits for fault-tolerance. These advances will pave the way to scalable, topologically protected circuits of electron spin qubits in quantum dots.

  QuBus test structure in SiGe Copyright: I. Seidler