cqed susceptibility of superconducting transmons coupled to a microstrip resonator cavity david...
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cQED Susceptibility of Superconducting Transmons coupled to a Microstrip Resonator Cavity
David Pappas, Martin Sandberg, Jiansong Gao, Michael VissersNIST, Boulder, CO 80303
Anton Kockum, Goran JohanssonChalmers University of Technology, Gӧteborg, Sweden
OutlineWhat do you do when your qubit
frequency is too close to your cavity? “Quantum art”
• Response of a coupled qubit-cavity system to a strong drive at finite temperature– Singly dressed - qubit + cavity– Doubly dressed system –
• qubit+cavity+ drive• two photon processes
– Triply dressed• three photon processes
“2½D” - Transmon coupled to microstrip cavity• Standard large-pad transmon,
GHz• Measured with microstrip cavity
– Measured at 20 mK– Radiation decay suppressed due to
proximity of ground plane• T1 2 - 10 s
– Coupling strength MHz– = 6.525 Ghz
• – Lifetime strongly Purcell limited– In resonant regime (not dispersive)
Sandberg, et al., APL 102, 072601 (2013)
Qubit
Cavity response to a probe toneVNA S21
probe
1 2
• Measure transmission, S21 at T∽100 mK• Susceptibility of the system
• frequency & power dependence• High power – bare cavity• Low power – excitation spectrum of
“singly dressed” qubit+cavity
cavity
Qubit-cavity excitations
High power
Low power
Model with Jaynes-Cummings Hamiltonian• Include 4 lowest qubit states, ,,, 3 lowest photon numbers in cavity, ,,
Excitation spectrum Transition Frequency (GHz)
0 - 7 18.5350 - 6 17.6500 - 5 13.2250 - 4 12.6601 - 7 12.4310 - 3 12.0032 - 7 11.9191 - 6 11.5462 - 6 11.0341 - 5 7.1210 - 2 6.6162 - 5 6.6091 - 4 6.5563 - 7 6.5320 - 1 6.1042 - 4 6.0441 - 3 5.8994 - 7 5.8753 - 6 5.6472 - 3 5.3875 - 7 5.3104 - 6 4.9905 - 6 4.4253 - 5 1.2226 - 7 0.8853 - 4 0.6574 - 5 0.5651 - 2 0.512
Line identificationTransition Frequency (GHz)
0 - 7 18.5350 - 6 17.6500 - 5 13.2250 - 4 12.6601 - 7 12.4310 - 3 12.0032 - 7 11.9191 - 6 11.5462 - 6 11.0341 - 5 7.1210 - 2 6.6162 - 5 6.6091 - 4 6.5563 - 7 6.5320 - 1 6.1042 - 4 6.0441 - 3 5.8994 - 7 5.8753 - 6 5.6472 - 3 5.3875 - 7 5.3104 - 6 4.9905 - 6 4.4253 - 5 1.2226 - 7 0.8853 - 4 0.6574 - 5 0.5651 - 2 0.512
cavitycavity
0-21-43-7
• Use low power probe tone to measure the system
• Add high power drive (i.e. pump) for susceptibilty
Susceptibility measurementVNA S21
probe
1 2
drive
Drive tone, D (GHz)