Nonreciprocity and Circulation in a Passive Josephson-Junction Ring.

Building large-scale superconducting quantum circuits will require miniaturization and integration of supporting devices including microwave circulators, which are currently bulky, stand-alone components. Here, we report the measurement of microwave scattering from a ring of Josephson junctions, with dc-only control fields. We detect the effect of quasiparticle tunneling, and dynamically classify the system at its operating design point into different quasiparticle sectors.

Coherent control of a donor-molecule electron spin qubit in silicon.

Donor spins in silicon provide a promising material platform for large scale quantum computing. Excellent electron spin coherence times of [Formula: see text] μs with fidelities of 99.9% have been demonstrated for isolated phosphorus donors in isotopically pure Si, where donors are local-area-implanted in a nanoscale MOS device.

Spin read-out in atomic qubits in an all-epitaxial three-dimensional transistor.

The realization of the surface code for topological error correction is an essential step towards a universal quantum computer. For single-atom qubits in silicon, the need to control and read out qubits synchronously and in parallel requires the formation of a two-dimensional array of qubits with control electrodes patterned above and below this qubit layer. This vertical three-dimensional device architecture requires the ability to pattern dopants in multiple, vertically separated planes of the silicon crystal with nanometre precision interlayer alignment.

Characterization of a Scalable Donor-Based Singlet-Triplet Qubit Architecture in Silicon.

We present a donor-based quadruple-quantum-dot device, designed to host two singlet-triplet qubits fabricated by scanning tunnelling microscope lithography, with just two leads per qubit. The design is geometrically compact, with each pair of dots independently controlled via one gate and one reservoir. The reservoirs both supply electrons for the dots and measure the singlet-triplet state of each qubit via dispersive sensing.