Hybrid Quantum Systems

This book presents state-of-the-art research on quantum hybridization,  manipulation, and measurement in the context of hybrid quantum systems.  It covers a broad range of experimental and theoretical topics relevant  to quantum hybridization, manipulation, and measurement technologies,  including a magnetic field sensor based on spin qubits in diamond NV  centers, coherently coupled superconductor qubits, novel coherent  couplings between electron and nuclear spin, photons and phonons, and  coherent coupling of atoms and photons. Each topic is concisely  described by an expert at the forefront of the field, helping readers  quickly catch up on the latest advances in fundamental sciences and  technologies of hybrid quantum systems, while also providing an  essential overview.

Table of contents
Preface
Contents
Control of Spin Coherence and Quantum Sensing in Diamond
1 Extension of Coherence Times of NV Centers in Diamond
1.1 Long Coherence Times and High Magnetic Sensitivity with NV Centres in Phosphorus-Doped n-type Diamond
1.2 Extension of the Coherence Time by Generating MW Dressed States in a Single NV Centre in Diamond
2 Electrical Control and Detection of Spin Coherence in Diamond
2.1 Electrical Control for Extension of Spin Coherence Times of NV Centers in Diamond
2.2 Room Temperature Electrically Detected Nuclear Spin Coherence of NV Centres in Diamond
2.3 Ferromagnetic-Resonance Induced Electromotive Forces in Ni81Fe19|p-Type Diamond
3 Quantum Hybrid Sensors
3.1 Hybrid Quantum Magnetic-Field Sensor with an Electron Spin and a Nuclear Spin in Diamond
3.2 ODMR of High-Density Ensemble of NV− Centers in Diamond
3.3 Optimization of Temperature Sensitivity Using the ODMR Spectrum of a NV Center Ensemble
References
Wide-Field Imaging Using Ensembles of NV Centers in Diamond
1 Introduction
2 Experimental Techniques for Wide-Field Imaging
2.1 Diamond Samples Used for Wide-Field Imaging
2.2 Experimental Technique
3 Optically Detected Magnetic Resonance
4 Ramsey Fringe
5 Frequency Modulation
6 Imaging of Microwave Intensity
7 Summary and Outlook
References
Collective Effects in Hybrid Quantum Systems
1 Introduction
2 Non-linear Effects
2.1 Amplitude Bistability in a HQS
2.2 Superradiance in a HQS
3 Quantum Effects
3.1 Applications
4 Summary and Perspectives
References
Rare Earth Non-spin-bath Crystals for Hybrid Quantum Systems
1 Rare-Earth Doped Crystals as Platform for Hybrid Quantum Systems
2 Magnetic Purification of Guest Ions
2.1 Growth of 167Er3+ Doped Y2SiO5
2.2 Spectral Hole Burning
2.3 Coherent Transients
3 Magnetic Purification of Host Crystal
3.1 (ErSc)2O3 Grown on Si Substrates
3.2 Er-Doped CeO2 Grown on Si Substrates
3.3 Photonic Structures on Epitaxial RE Oxide
4 Summary
References
Electron Spin Resonance Detected by Superconducting Circuits
1 Introduction
1.1 Superconducting Quantum Circuits
1.2 Local Electron Spin Resonance
2 ESR Using dc-SQUID
2.1 Experimental Setup
2.2 Magnetometry
2.3 ESR Spectroscopy
2.4 Estimation of Sensing Volume and Sensitivity
3 ESR Using a Josephson Bifurcation Amplifier
3.1 Josephson Bifurcation Amplifiers
3.2 ESR Spectroscopy Setup
3.3 ESR Spectroscopy of Er:YSO Using a JBA
3.4 Measurement Sensitivity
4 ESR Detected by a Flux Qubit with Switching Readout
4.1 Experimental Setup
4.2 Magnetometry
4.3 ESR Spectroscopy
4.4 Estimation of Sensitivity
5 ESR Detected by a Flux Qubit with JBA Readout
5.1 ESR Spectroscopy Setup
5.2 ESR Spectroscopy of Er:YSO
5.3 Measurement Sensitivity and 1/f Flux Noise
6 Summary and Perspectives
References
Hybrid Quantum Systems with Spins in Diamond Crystals and Superconducting Circuits
1 Introduction
2 Impurity Spins in Diamond
2.1 NV Centers in Diamond
3 Circuit Quantum Electrodynamics
3.1 Superconducting Resonators: Quantum LC Oscillators
3.2 Superconducting Qubits
4 Spin Ensemble Quantum Memories for Microwave Photons
4.1 Strong Coupling of a Spin Ensemble  to a Superconducting Resonator
4.2 Coherent Coupling of a Superconducting Qubit  and a Spin Ensemble
4.3 Towards a Spin-Ensemble Quantum RAM
5 Summary and Perspective
References
High-Temperature Spin Qubit in Silicon Tunnel Field-Effect Transistors
1 Background and Core Technology
2 Electrically Accessing a Deep Impurity
3 Device and Measurement
4 Single Electron Transport at Room Temperature
5 Double-Quantum-Dot Transport
6 Spin Blockade and Qubit
7 Quantum Interference
8 Other Devices
9 Outlook
References
Ge/Si Core–Shell Nanowires for Hybrid Quantum Systems
1 Introduction
2 Evaluation of the Strength of Spin–Orbit Interaction
2.1 Spin–Orbit Interaction in a Ge/Si Nanowire
2.2 Weak (Anti-)localization
2.3 Dual Gated Device
2.4 Electrical Modulation of Spin–Orbit Interaction
3 Detection of Helical Spin State in Ge/Si Core/Shell Nanowire
3.1 Principle
3.2 Experimental Considerations
3.3 Helical State Studies in III–V Nanowires
3.4 Hole Helical State Detection in Ge/Si Nanowires
4 Toward Spin-Photon Coupling
4.1 Double Quantum Dot Embedded in a Superconducting Cavity
4.2 Model
4.3 Charge Stability in a Double Quantum Dot
4.4 Tunable Charge Dipolar Coupling
5 Summary
References
Photonic Quantum Interfaces Among Different Physical Systems
1 Introduction
2 Quantum Frequency Conversion (QFC)
2.1 Second-Order Nonlinear Optical Interaction
2.2 Theory and Background for QFC
2.3 QFC for Optical-Fiber-Based Quantum Network
3 Atom-Photon Quantum Interface
3.1 Atomic Ensemble Quantum Memory
3.2 Atom-Photon Entanglement
3.3 Summary
4 Optomechanical Interface
4.1 Basic Optomechanical Operation
4.2 Composite Cavity Optomechanical Architecture
4.3 External Cavity Architecture
4.4 Summary
5 Conclusions
References
Hybrid Quantum System of Fermionic Neutral Atoms in a Tunable Optical Lattice
1 Introduction
1.1 Outline of This Chapter
2 Spatial Adiabatic Passage in a Lieb Lattice
2.1 Three-Level System with Λ-type Transition
2.2 Lieb Lattice
2.3 Optical Lieb Lattice
2.4 Correspondence Between a Three-Level System and Lieb Lattice
2.5 Spatial Adiabatic Passage (SAP)
2.6 Autler-Townes Doublet
2.7 Conclusion
3 Antiferromagnetic Spin Correlation of SU(N) Fermi Gas in an Optical Dimerized Lattice
3.1 Local Entropy Redistribution
3.2 SU(mathcalN) Fermi-Hubbard Hamiltonian in a Dimerized Cubic Lattice
3.3 Optical Dimerized Lattice Potential
3.4 Spin Manipulation by Optical Pumping
3.5 Singlet-Triplet Oscillation (STO) in Dimer
3.6 Comparison Between SU(4) and SU(2) Systems
3.7 Conclusion
4 Summary and Outlook
4.1 Outlook
References
Phonon-Electron-Nuclear Spin Hybrid Systems in an Electromechanical Resonator
1 Introduction
2 Experimental Methods
2.1 Fabrication of an Electromechanical Resonator
2.2 Transport Measurements for an Electromechanical Resonator
3 Displacement Sensing with Quantum Dot and Point Contact
3.1 Displacement Transducers with QPC and QD
3.2 Thermal Motion Measurements and Displacement Sensitivity
4 Nuclear Spin Manipulation with an Electromechanical Resonator
4.1 Mechanical Resonator Quadrupole-Coupled with Nuclear Spins
4.2 Experimental Observation of Mechanical ac-Stark Shift
References
Cavity Quantum Electrodynamics with Laser-Cooled Atoms and Optical Nanofibers
1 Introduction
2 Cavity QED
2.1 Jaynes–Cummings Model
2.2 Dissipations
2.3 Dynamics
2.4 Deterministic Generation of Single Photons
2.5 Input and Output
2.6 Transfer Matrix Method
3 Nanofiber Cavity QED
3.1 Strong Coupling with a Nanofiber Cavity and Single Trapped Atoms
3.2 Fabrication of Low-Loss Tapers
3.3 Fabrication of Low-Loss FBGs
4 Coupled Cavities QED
5 Outlook
References
Robust Quantum Sensing
1 Introduction
2 Magnetic Field Sensing with Qubits Without Decoherence
3 Magnetic Field Sensing with Entangled States Without Decoherence
4 Dephasing on the Qubit
5 Magnetic Field Sensing with Separable States Under the Effect of Dephasing
6 Magnetic Field Sensing with Entangled States Under the Effect of Dephasing
7 Suppression of the Dephasing by Quantum Teleportation
8 Magnetic Field Sensing with Quantum Teleportation Under the Effect of Dephasing Using Separable States
9 Magnetic Field Sensing with Quantum Teleportation Under the Effect of Dephasing Using Entangled States
10 Magnetic Field Sensing with Imperfect Quantum Teleportation Under the Effect of Dephasing Using Separable States
11 Magnetic Field Sensing with Imperfect Quantum Teleportation Under the Effect of Dephasing Using Entangled States
12 Conclusion
References
Transferring  Quantum Information in Hybrid Quantum Systems Consisting of a Quantum  System with Limited Control and a Quantum Computer
1 Introduction
2 Settings
2.1 Assumptions for a Physical System Coupling  to a Quantum Computer
3 Approximate IO Operations Evaluated in Terms of the Diamond Norm
4 The LS Algorithm
4.1 Quantum Circuit Representation of the Algorithm
4.2 Necessary Conditions for SN(Uint)
4.3 Implementing WN(Uint) by Applying Uint
5 The CS Algorithm
5.1 Algorithm
5.2 Conditions for Interface Unitary Operators
6 Final Adjustment of Input-Output Algorithms
6.1 Corrections for the Effects of HS
6.2 Designing Input Operations
7 Effective Interface
8 Conclusion
9 Appendix
9.1 Proof of Lemma 1
9.2 The Details of the CS Algorithm
References