Speaker: Rohit Navarathna
Affiliation: University of Queensland


Non-reciprocal devices such as circulators are used to route signals to different parts of a circuit. They can also be used as isolators, which are used to help protect the fragile quantum system from noise that is generated by an amplifier mounted at a higher temperature stage, while still allowing the signal from the system to be amplified.

Commercial ferrite circulators are big, bulky and have permanent magnets which make them unsuited for integration with superconducting circuits. Fabrication of a circulator on a chip will help in miniaturising the circuit elements without disrupting the qubits which are extremely sensitive to magnetic flux noise. It will also allow hundreds of circulators to be used on a single chip, which allows for larger networks of quantum systems.

I will be showing you the progress on a prototype for a passive superconducting on-chip circulator and some of the problems we face in characterizing the device. This will involve some changes in the design of the circulator, including the addition of a DC electrode to mitigate charge noise, and traps to reduce quasiparticle tunnelling.

About Physics Seminars

The weekly Physics Seminar series focuses on a broad range of physics research within SMP, along with frequent presentations from visiting researchers. Seminars are usually scheduled for 1.00pm on Tuesdays.

The talks are typically more specialised than a colloquium but are often attended by staff and PhD students across a broad range of areas. Speakers are thus encouraged to include introductory material in the talks.

All SMP researchers and HDR students are encouraged to speak. Please email Tyler Neely to register your interest.

The seminars are open so there is no need to register your attendance.

Previous recorded physics seminars 


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