uri physics colloquium

Encoded qubit approach to superconducting quantum computing

Dr. Utkan Güngördü

Wednesday, January 29, 2020

4 pm, East Hall Room 112

abstract

Quantum computers can solve a certain class of problems exponentially faster than their classical counterparts. Qubits, which are the building blocks of a quantum computer, tend to be very sensitive to external disturbances. Achieving robust control of qubits in the presence of noise is essential for building a reliable and useful quantum computer.

It is envisioned that surface codes, a class of error correction codes for qubits, can be used to achieve this goal, once the error rates of the noisy quantum gates are brought down below the corresponding threshold level. Recent advances in experimental techniques in solid state qubits have significantly improved the error rates of single-qubit gates, nearing this fault-tolerance threshold. However, a useful quantum computer also requires multi-qubit operations to entangle the qubits, and the fidelities of such operations remain lower.

Among solid state qubits, semiconductor-based platforms have favorable coherence times, which is the timescale that qubits can retain their state. Silicon, in particular, is promising due to established fabrication techniques and the spinless nuclei of its most abundant isotope 28Si, which leads to further improvement of coherence times. In this talk, I will give an overview of quantum dots which host the physical qubits in semiconductor platforms, discuss the physical sources of errors, and present quantum control methods to boost the fidelities of single- and two-qubit gates with a focus on silicon-based spin qubits.