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

“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

Kyle Keane and Alexander N. Korotkov What has been done? Slide 3/8 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

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

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

Time Dependence of Couplers Slide 6/8   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

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

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

Ideal Estimates and Deviations Slide 9/8 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

Kyle Keane and Alexander N. Korotkov Timing Errors Slide 10/8   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

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

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

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

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