Simulating Supercool Quantum Bits (Qubits)

Using High Frequency Structure Simulator (HFSS)

This material is based upon work supported by the National Science Foundation

under Grant No. EEC-0540832.

Neno Fuller1, Yanbing Liu2, Andrew Houck2, 1 – Brooklyn College, Brooklyn, NY, 11210, USA

2 – Princeton University, Princeton, NJ, 08544, USA

www.mirthecenter.org

There are many

approaches to QC. We

study cavity quantum

electrodynamics (cQED)

where our qubit is a

superconducting circuit

called the “transmon”.

1. Interaction between the environment and qubit reduces

qubit lifetime

2. Use of filters to remove unwanted electromagnetic modes

3. Utilize purcell effect to increase lifetime (T1) of qubit

Background

Motivation

Simulation

The basic unit of

information in classical

computing is represented

by a “bit”. In quantum

computing (QC) it is a

“qubit”

Schematic representation of the filter: Zlo

and Zhi represent different characteristic

impedances

This is our simulated filter. The alternating

shades of yellow and green on the plane

of the device represent the alternating

impedances.

The tetrahedral sections are part of the

mesh of HFSS. These are the finite

elements used to solve Maxwell's

equations within the device.

Data & Analysis

• Model qubit coupled to

filter

• Calculate T1 from HFSS

admittance data

• Utilize HFSS for circuit

optimization

• Add more steps to

filtration

Future Work

I would personally like to thank Professor Andrew Houck,

Yanbing Liu and the entire Houck lab for their patience

and guidance.

The high frequency structure simulator (HFSS) is a finite element method solver for

electromagnetic structures. We use it to simulate the cavity and filter.

We model the filter using two

approaches: HFSS and Microwave

Office (AWR).

HFSS includes the electromagnetic

environment while modeling the filter;

whereas AWR does not.

On the top left we see HFSS’s

frequency response of the filter. Below

that we have AWR’s.

Qualitatively, the two responses

agree. However, in the HFSS result,

we see a slight bump around 7.60

GHz. This may be indicative of an

environmental effect.

Conclusion

• HFSS models the

components of our

system correctly

• Problems modeling full

system which has more

to do with incorrect

modeling parameters

We would like to thank

MIRTHE and our fellow

MIRTHE scholars for a

enriching and prosperous

summer experience.

Acknowledgments

The purcell filter is

composed of five

coplanar waveguides

of alternating

impedances.

Device image of

superconducting purcell

filter