Grèzes Towards a Spin-Ensemble Quantum Memory for Superconducting Qubits

Design and Implementation of the Write, Read and Reset Steps
1. Auflage 2016
ISBN: 978-3-319-21572-3
Verlag: Springer Nature Switzerland
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 240 Seiten

Reihe: Springer Theses

This work describes theoretical and experimental advances towards the realization of a hybrid quantum processor in which the collective degrees of freedom of an ensemble of spins in a crystal are used as a multi-qubit register for superconducting qubits. A memory protocol made of write, read and reset operations is first presented, followed by the demonstration of building blocks of its implementation with NV center spins in diamond. Qubit states are written by resonant absorption of a microwave photon in the spin ensemble and read out of the memory on-demand by applying Hahn echo refocusing techniques to the spins. The reset step is implemented in between two successive write-read sequences using optical repumping of the spins.

Cécile Grèzes received the B.S. degree from the Ecole Normale supérieure, Paris, France, in 2009 and her Ph.D. from the University Paris VI in 2014. Her thesis work was performed at the Commissariat à l'énergie atomique on experimental quantum information processing with Josephson superconducting circuits and spins in crystal. Since 2015, she has been working on the development of nonvolatile magnetic memory in the electrical engineering department at the University of California Los Angeles.

Autoren/Hrsg.

Grèzes, Cécile

Inhaltsverzeichnis

1;Supervisor's Foreword;6
2;Acknowledgments;8
3;Abstract;9
4;Contents;11
5;1 Introduction;15
5.1;1.1 Rationale for the Hybrid Way;15
5.2;1.2 Spin Ensemble Quantum Memory Principle;18
5.3;1.3 Storing a Qubit State in a Spin Ensemble (Write);20
5.4;1.4 Retrieving Few-Photon Fields Stored in a Spin Ensemble (Read);24
5.5;1.5 NV Clock Transitions for Long Coherent Storage;27
5.6;1.6 Towards an Operational Quantum Memory;28
5.7;References;30
6;2 Background;33
6.1;2.1 Superconducting Circuits and Microwave Engineering;33
6.1.1;2.1.1 Superconducting Resonators;33
6.1.2;2.1.2 Josephson Junction Based Circuits;43
6.1.3;2.1.3 Circuit Quantum Electrodynamics;53
6.2;2.2 NV Center Spins in Diamond;59
6.2.1;2.2.1 Structure;59
6.2.2;2.2.2 The NV Center Spin Qubit;60
6.2.3;2.2.3 Coherence Times;65
6.3;2.3 Coupling Ensembles of NV Center Spins to Superconducting Circuits;67
6.3.1;2.3.1 Single Spin-Resonator Coupling;67
6.3.2;2.3.2 Spin Ensemble-Resonator Coupling: Collective Effects;68
6.3.3;2.3.3 The Resonator-Spins System in the Low-Excitation Regime;79
6.3.4;2.3.4 The Resonator-Spins System Under Strong Drive Powers;88
6.4;References;89
7;3 Proposal: A Spin Ensemble Quantum Memory for Superconducting Qubits;92
7.1;3.1 Spin-Based Quantum Memory;92
7.1.1;3.1.1 Motivations;92
7.1.2;3.1.2 Spin Ensemble Quantum Memory: Principles;93
7.2;3.2 Spin Ensemble Quantum Memory Protocol;95
7.2.1;3.2.1 The Write Step: Storage of N Quantum States |?1rangleƒ|?nrangle;95
7.2.2;3.2.2 The Read Step: On-Demand Retrieval of |?irangle;96
7.2.3;3.2.3 The Full Quantum Memory Protocol;99
7.3;3.3 Simulations;100
7.4;References;102
8;4 Experiment 1 (Write): Coherent Storage of Qubit States into a Spin Ensemble;105
8.1;4.1 State of the Art and Principle of the Experiment;105
8.1.1;4.1.1 State of the Art;105
8.1.2;4.1.2 Strong Coupling of NVs to a Superconducting Resonator;106
8.1.3;4.1.3 Principle of the Experiment;108
8.2;4.2 Experimental Realization;110
8.2.1;4.2.1 The Hybrid Quantum Circuit;110
8.2.2;4.2.2 Measurement Setup;116
8.3;4.3 Operating the Hybrid Quantum Circuit;122
8.3.1;4.3.1 Superconducting Circuit Characterization;122
8.3.2;4.3.2 Transferring Qubit States to the Bus Resonator;130
8.3.3;4.3.3 Coupling the NV Spin Ensemble to the Bus Resonator;132
8.4;4.4 Storage of Qubit States into a NV Spin Ensemble;134
8.4.1;4.4.1 Storing a Single Photon from the Qubit into the Spin Ensemble;134
8.4.2;4.4.2 Storing a Coherent Superposition from the Qubit to the Spin Ensemble;138
8.4.3;4.4.3 Entanglement Between the Spin Ensemble and the Resonator;141
8.5;4.5 Conclusions on Experiment 1: The Write Step;143
8.6;References;144
9;5 Experiment 2 (Read): Multimode Retrieval of Few Photon Fields from a Spin Ensemble;145
9.1;5.1 Principle of the Experiment;145
9.2;5.2 Experimental Realization;147
9.2.1;5.2.1 The Hybrid Quantum Circuit;147
9.2.2;5.2.2 Measurement Setup;151
9.3;5.3 Spectroscopy of the Resonator-Spins System;157
9.3.1;5.3.1 Characterization of the Resonator;158
9.3.2;5.3.2 System Spectroscopy at Zero-Magnetic Field;159
9.4;5.4 Active Reset of the Spins;162
9.4.1;5.4.1 Effect of Light Irradiation on the Superconducting Resonator;162
9.4.2;5.4.2 Continuous Irradiation: Dependence of the Spin Polarization on the Optical Power;168
9.4.3;5.4.3 Pulsed Irradiation: Active Spin Polarization;172
9.4.4;5.4.4 Spin Relaxation Time Measurement;177
9.5;5.5 Multimode Retrieval of Few Photon Fields Stored in a Spin Ensemble;178
9.5.1;5.5.1 Applying Hahn Echoes to the Spin Ensemble;178
9.5.2;5.5.2 Retrieval of Few-Photon Pulses Stored in the Spin Ensemble;186
9.6;5.6 NV Clock Transitions for Long Coherent Storage;193
9.6.1;5.6.1 Atomic Clock Transitions in NV Centers in Diamond;193
9.6.2;5.6.2 Full System Spectroscopy;194
9.6.3;5.6.3 Dependence of the Echo Coherence Time on the Magnetic Field;197
9.6.4;5.6.4 Advanced Analysis: Spin Classes Contributions to the Echo Decay;201
9.7;5.7 Conclusion on Experiment 2: The Read Step;207
9.8;References;209
10;6 Towards an Operational Quantum Memory;210
10.1;6.1 Reaching Efficient Memory Operations;210
10.1.1;6.1.1 Storage and Retrieval of Photon Fields at the Single Photon Level with Improved Efficiencies;210
10.1.2;6.1.2 Reaching the Operational Level;216
10.2;6.2 Running the Full Quantum Memory Protocol;218
10.2.1;6.2.1 Step 1/2: Realization of a Frequency Tunable Resonator Compatible with Refocusing Pulse Applications;218
10.2.2;6.2.2 Realizing a Hybrid Circuit Able to Run the Full Memory Protocol;226
10.3;References;229
11;7 Conclusions and Perspectives;230
11.1;References;232
12;Appendix AFabrication;233
13;Appendix BNV Center Distribution;235
14;Curriculum Vitae;238