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Abstracts
P4.14
Observation of high-order transitions in a superconducting qubit
coupled to coplanar waveguide cavity
Yu-Cheng Chang, Ze-Yan Chen, Jyh-Yang Wang, Teik-Hui Lee, Teik-Hui Lee,
Myrron A. Aguila, Joshoua Esmenda and Chii-Dong Chen
Institute of Physics, Academia Sinica, Taipei 115, Taiwan
Coherent interaction between a superconducting transmon quantum bit and an
on-chip superconducting cavity is studied. The transmon consists of a SQUID
whose transition frequency between the two lowest levels of the transmon can be
tuned continuously by the applied external magnetic flux threading the SQUID
loop. As this level spacing is tuned to close to the resonance frequency of the Nb
superconducting cavity, the Rabi-splitting feature emerges, indicating a coherence
coupling between the qubit and the cavity. In addition, the higher-order transitions
involving 2nd and 3rd excitation levels and multiple photons are observed, but
there are no sign of qubit-cavity coupling.
P4.15
Inductively Coupled Superconducting Quantum Interference
Device Transduction of Nanoelectromechanical Systems at Low
Temperatures
Rupert Mellor (1), Andrew Casey (1), Brian Cowan (1), Chris Lusher (1), Kunal
Lulla (1,2), John Saunders (1)
1) Department of Physics, Royal Holloway, University of London, UK
2) Now at Department of Physics, Lancaster University, UK
We present work on high Q Nanoelectromechanical systems (NEMS) at millikelvin
temperatures, transduced via a Superconducting Quantum Interference Device
(SQUID) in low magnetic fields (200mT). In this technique, the NEMS is
inductively coupled to the SQUID, mounted far from the magnet, allowing
flexibility in magnetic field without affecting SQUID behaviour. A SiN dobly
clamped beam (300
µ
m x 250nm x 100nm), has been characterised from 3K to
21mK, observing thermally driven motion. We observe tuneable feedback effects
between the SQUID and the NEMS, resulting in self-sustained oscillations with
stability greater than 8ppb.
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