Jonas Helsen

A crossbar network for silicon quantum dot qubits

Quantum dots take a shortcut toward practical quantum information. The spin states of single electrons in gate-defined quantum dots satisfy crucial requirements for a practical quantum computer. These include extremely long coherence times, high-fidelity quantum operation, and the ability to shuttle electrons as a mechanism for on-chip flying qubits. To increase the number of qubits to the thousands or millions of qubits needed for practical quantum information, we present an architecture based on shared control and a scalable number of lines. Crucially, the control lines define the qubit grid, such that no local components are required. Our design enables qubit coupling beyond nearest neighbors, providing prospects for nonplanar quantum error correction protocols. Fabrication is based on a three-layer design to define qubit and tunnel barrier gates. We show that a double stripline on top of the structure can drive high-fidelity single-qubit rotations. Self-aligned inhomogeneous magnetic fields induced by direct currents through superconducting gates enable qubit addressability and readout. Qubit coupling is based on the exchange interaction, and we show that parallel two-qubit gates can be performed at the detuning-noise insensitive point. While the architecture requires a high level of uniformity in the materials and critical dimensions to enable shared control, it stands out for its simplicity and provides prospects for large-scale quantum computation in the near future.

Representations of the multi-qubit Clifford group

The Clifford group is a fundamental structure in quantum information with a wide variety of applications. We discuss the tensor representations of the

Quantum error correction in crossbar architectures

q

Device-independence for two-party cryptography and position verification

-qubit Clifford group, which is defined as the normalizer of the

How to transform graph states using single-qubit operations: computational complexity and algorithms.

q

Multiqubit Randomized Benchmarking Using Few Samples

-qubit Pauli group in

Practical and reliable error bars for quantum process tomography

U(2^q)

Efficient Unitarity Randomized Benchmarking of Few-qubit Clifford Gates.

. In particular, we characterize all irreducible subrepresentations of the two-copy representation

A new class of efficient randomized benchmarking protocols

\varphi^{\otimes2}

Device independence for two-party cryptography and position verification with memoryless devices

of the Clifford group on the matrix space