ocs_transmon_qubit's Introduction

Goal:

Design an OCS qubit with $\frac{E_j}{E_c} \approx 20$ for fabrication through Lincoln Lab, MIT.

Constraints:

Resonator frequency between 4 - 12 GHz (due to circulator, amplifiers and mixers)
$\omega_{res} \approx \omega_{03}$ of qubit
$\omega_{03} = 3 \omega_{01} - 2 * α$
$\omega_{01}$ needs to be between 2 and 6 GHz

Isolate qubit + claw design from standard candle qubit design a. JJ is not an element in Ansys so might need to use Lumped Element Linear Inductor with the correct $L_j$ value instead
Simulate (EPR) the qubit+ claw design to get $E_c , \omega_{01}, \alpha$

a. Ensure hyperparameters meet LL SQUILL Foundry requirements

b. Claws as port

c. No other components on chip

d. Be careful of mesh parameters
```
 - maximum meshing size should be at least half of smallest feature
 - Define mesh resolution for separate components according to the rule ^
```
e. Calculate $E_j$
```
 - $\hbar \omega_{01} = \sqrt(8 E_j E_c) - E_c $
```
f. Change simulation parameters (i.e. qubit + claw + JJ parameters) to get $E_j/E_c \approx 20$
Compute $\omega_{03}$
Simulate (S21) a claw + CPW resonator + 2-port transmission line from the standard candle qubit design

a. Get $\omega_{res}$ - Fit with lflPython/fitTools/Resonator.py tool

b. Change resonator length to get $\omega_{res} = \omega_{03}$
Choose 5 physical parameters of the qubit that have $E_j/E_c \in (10,30)$ (steps 1 and 2)
Get $\omega_{res}$ for these new qubits (steps 3 and 4)
Adjust the GDS file with the final chip design to comply with LL SQUILL Submission Requirements

a. Get the JJ length for each qubit
```
 - $L_j$ from $E_j$

 - `L_j = junction_area * critical_current_density`

 - `Junction_area = JJ_length * JJ_width`
```

Recommend Projects