1. Modeling a Flying Microwave Qubit
Slide 1/8
Transferring Quantum Information Using Superconducting Waveguides
Kyle Keane
Alexander N. Korotkov
FUNDING AGENCIES
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

2. “INTERMEDIATE RESULTS” Kyle Keane and Alexander N. Korotkov
Introduction
Slide 2/8
OPERATIONS
“ALICE”
“PRE-PROCESSOR”
“INTERMEDIATE RESULTS”
What is a Flying Qubit?
Qubit that moves information between two processing or storage sites
TRANSFER
Why do we need them?
Communication between two parties or nodes in a modular quantum computer
“Flying Qubit”
OPERATIONS
“BOB”
“PROCESSOR”
“COMPUTATION”
What do we look at?
Microwave in a superconducting transmission line
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

3. Kyle Keane and Alexander N. Korotkov
What has been done?
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Jahne, Yurke, Gavish: Proposed protocol with one tunable coupler
Cirac, Zoller, Kimble, Mabuchi: ???
Braunstein, Kimble: ???
Razavi, Shapiro: ???
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

4. Kyle Keane and Alexander N. Korotkov
System
Slide 4/8
High-Q Storage
Tunable Couplers
Example from UCSB
Coplanar Waveguide or
Phase Qubit
Transmission Line 1
Superconducting Waveguide
Tunable Parameter
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

5. Kyle Keane and Alexander N. Korotkov
Main Idea
Slide 5/8
SYSTEM
HIGH-Q (WEAK COUPLING)
This is still not a trivial problem
CANCEL BACK REFLECTION
Need INTERFERENCE
“back into line”
r B B
t B
r A A
t A
“into resonator”
Transmission line
Receiving resonator
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

6. Time Dependence of Couplers
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DEFINITIONS
1. WANT VOLTAGE FLOWING IN ONLY
2. EASIER TO THINK OF IT FLOWING OUT ONLY TL R TL R
3. TIME REVERSAL OF FLOWING OUT ONLY
GIVES OUR NEEDED TIME DEPENDENCE
4. REQUIRES SPECIFIC CONTROL OF FIRST COUPLER TL R
REQUIRES
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

7. Achieving Near-Perfect Transfer
Slide 7/8
Qubit
initially
is here
Qubit
transferred
to here
Transmission
Coefficients
Time (t)
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

8. Second Half = Time Reversal
Slide 8/8
Qubit
initially
is here
Qubit
transferred
to here
Transmission
Coefficients
Time (t)
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

9. Ideal Estimates and Deviations
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Qubit
initially
is here
Qubit
transferred
to here
Transmission
Coefficients
Time (t)
UCSB ? ?
MAX
Transmission
Coefficients
Time (t)
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

10. Kyle Keane and Alexander N. Korotkov
Timing Errors
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Transmission
Coefficients
Time (t)
Fidelity (η)
For 420 ns
protocol
This is 25 ns
synchronized timing is very important
Designed for
η=0.999
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

11. Kyle Keane and Alexander N. Korotkov
Maximum Coupling
Slide 11/8
Transmission
Coefficients
Time (t)
Designed for
η=0.999
Fidelity (η)
Identical couplers are important
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

12. Kyle Keane and Alexander N. Korotkov
Resonator Q Factor
Slide 12/8
MAX
Transmission
Coefficients
Time (t)
Equal Q-factors are not very important
Fidelity (η)
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

13. Known Frequency Mismatch
Slide 13/8
Fidelity (η)
Detuning (MHz)
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov

14. Kyle Keane and Alexander N. Korotkov
Conclusions
Slide 14/8
something
something
Other Considerations
Multiple reflections
Lossy materials
Flying Microwave Qubit
Kyle Keane and Alexander N. Korotkov