Main goal: measure Rigetti qubits inside 3 GHz cavities.
Schematics of the fridge can be found here:
Warm electronics and warm switches schematics is located here https://cdcvs.fnal.gov/redmine/projects/runs/repository/dr1_run_8/revisions/master/raw/DR1_run_8_warm_RF.pdf
Everything can be controlled from Labber including warm switches, but cryo switches are still controlled manually.
We have several devices installed:
1) RI-1 (TERI001) 3 GHz cavity with Rigetti qubit + eccosorb filter. Cavity is located on the side.
2) RI-2 (TERI002) 3 GHz cavity with Rigetti qubit + eccosorb filter. Cavity is located in the center.
3) Pappas' qubit + added 10 dB more in the last attenuator. (see: https://cdcvs.fnal.gov/redmine/issues/24199 )
4) McDermott's qubit is same as last DR1_run_7.
5) Pappas' 5 GHz JPA (see: https://cdcvs.fnal.gov/redmine/issues/22808#note-18 )
6) Pappas' 3 GHz JPA
7) Lincoln Lab TWPA (see: https://cdcvs.fnal.gov/redmine/issues/22808#note-12 )
#1 Updated by Taeyoon Kim about 2 months ago
I checked the GDS file that the Rigetti team sent, and I found the dimensions are a bit modified from what I sent. But the parameters are not hugely changed(actually they got slightly better!), so it would be okay to use it.
One chip(A2-c1-b1) has very low inductance, so has large qubit frequency(7.66 GHz) and low coupling(<2 kHz). I don’t think it will work as a qubit.
The other chip(A2-g1-b1) is fine. The specs are
Qubit freq: 4.89 GHz
Qubit anharmonicity: 72.86 MHz
Readout freq: 6.211 GHz
Qubit-fundamental coupling : 85 kHz
Qubit-readout coupling : 3.6 MHz
Fundamental mode Q-factor: ~10^6
Readout mode Q-factor: ~10^5
#5 Updated by Daniil Frolov about 2 months ago
estimation of TI-1 Q from decay (slightly better than TI-2)
decay time from -64 dB to e times (green line) = 39 ms
Q = pi * 3E+9 * 39E-3 = 3.67E+8
Attenuation through the cavity is ~15 dB higher.
Also attached raw data in "decay_RI-1.csv"
#6 Updated by Daniil Frolov about 2 months ago
CW measurement of chi_0 shift of fundamental mode of RI-2 cavity.
High power(20dBm, black)
Low power(-10dBm, blue)
chi_0 shift = 58.89 Hz
#7 Updated by Daniil Frolov about 2 months ago
Tried to test pulsed setup with new switches: measured Pappas' qubit readout. As expected, power levels went down by 10 dB because of new additional attenuation.
#8 Updated by Roman Pilipenko 22 days ago
DR warmed up and opened, as per e-mail from Alexander Romanenko from: Sep 26, 2020:
"...the problem is that the antenna coupling is too weak, and the resulting signal is too weak as well.
...6.19 GHz peak is floating around with minimal changes in temperature (even around 14-16 mK), that’s why it’s virtually impossible to measure its shift etc, as when you average and it moves around, it actually disappears.The same could be likely happening with the TM010 mode too...
...plan to change the antennas to stronger..."