On the route towards a useful quantum computer, we must not ignore the materials challenges facing us nor the opportunities that materials science may provide for disruptive new qubits.

Graphene qubit motivates materials science (nature.com)

We theoretically model the spin-orbit interaction in silicon quantum dot devices, relevant for quantum computation and spintronics. Our model is based on a modified effective mass approach which properly accounts for spin-valley boundary conditions, derived from the interface symmetry, and should have applicability for other heterostructures. We show how the …

We present a theory for understanding the exchange interaction between electron spins in neighboring quantum dots, either by changing the detuning of the two quantum dots or independently tuning the tunneling barrier between quantum dots. The Hubbard model and a more realistic confining-potential model are used to investigate how the …

We investigate a hybrid quantum system consisting of spatially separated resonant exchange qubits, defined in three-electron semiconductor triple quantum dots, that are coupled via a superconducting transmission line resonator. Drawing on methods from circuit quantum electrodynamics and Hartmann-Hahn double resonance techniques, we analyze three specific approaches for implementing resonator-mediated two-qubit …

We introduce an always-on, exchange-only (AEON) qubit made up of three localized semiconductor spins that offers a true “sweet spot” to fluctuations of the quantum dot energy levels. Both single- and two-qubit gate operations can be performed using only exchange pulses while maintaining this sweet spot. We show how to …

Superconducting circuits offer tremendous design flexibility in the quantum regime culminating most recently in the demonstration of few qubit systems supposedly approaching the threshold for fault-tolerant quantum information processing. Competition in the solid-state comes from semiconductor qubits, where nature has bestowed some very useful properties which can be utilized for …

M. Veldhorst, R. Ruskov, C. H. Yang, J. C. C. Hwang, F. E. Hudson, M. E. Flatté, C. Tahan, K. M. Itoh, A. Morello, and A. S. Dzurak

Spin qubits composed of either one or three electrons are realized in a quantum dot formed at a Si/SiO2 interface in …

Rusko Ruskov, Charles Tahan

An ultrasound transducer (“the wand”) both creates and detects sound waves that travel through the body to create images of internal organs or precious cargo (see the figure, panel A). This compact device is made possible with piezoelectric crystals that expand or contract in response to …

Yun-Pil Shim, Charles Tahan

Recent improvements in materials growth and fabrication techniques may finally allow for superconducting semiconductors to realize their potential. Here, we build on a recent proposal to construct superconducting devices such as wires, Josephson junctions, and qubits inside and out-of single crystal silicon or germanium. Using atomistic …

Yun-Pil Shim, Charles Tahan

Superconducting circuits are exceptionally flexible, enabling many different devices from sensors to quantum computers. Separately, epitaxial semiconductor devices such as spin qubits in silicon offer more limited device variation but extraordinary quantum properties for a solid-state system. It might be possible to merge the two approaches …