The Physics & Astronomy Colloquium Series presents Andreas Fuhrer for IBM Research of Zurich, discussing “From Qubits to Transistors and Back" on Jan. 21.

Colloquia are Fridays at 4:10 p.m.

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Abstract: Superconducting qubits have seen tremendous improvements in coherence over the past decade facilitated by improved circuit design, fabrication processes, integrated packaging and dedicated control hardware. However, qubit coherence is known to depend on the microscopic environment near the Josephson junctions affected e.g. by molecular adsorbates or amorphous oxides. In order to study the impact of such defects we have developed a UHV-treatment system that allows us to clean the qubit chips using UV-light, ion milling or active reagents such as ammonia before loading the chips into the dilution refrigerator under vacuum. We show how these treatments affect qubit coherence and can be used to trim the qubit frequency of fixed frequency transmons after fabrication and without affecting coherence.

Future universal quantum computing systems will require many such physical qubits in order to correct for errors that occur e.g. due to the presence of defects. It is thus a highly attractive prospect to Utilize the ultra-scaled fabrication processes of classical transistor fabrication for qubit fabrication. We show how silicon fin field-effect-transistors can be used as spin qubits. These devices have the advantage of being much smaller than superconducting qubits and can be operated at temperatures up to 4K. This may allow for more integrated classical control circuitry near the qubit devices, alleviating some of the challenges with the much higher device density in spin qubits.