Semiconductor Quantum Bits

✍ Scribed by Oliver Benson

• Year: 2008
• Tongue: English
• Leaves: 515
• Category: Library

✦ Synopsis

This book highlights the state-of-the-art qubit implementations in semiconductors, providing an extensive overview of this newly emerging field. Semiconductor nanostructures have huge potential as future quantum information devices as they provide simultaneously various ways of qubit implementation (electron spin, electronic excitation) as well as a way to transfer quantum information from these stationary qubits to flying qubits (photons). For this reason, this book unites contributions from leading experts in the field, reporting cutting-edge results on spin qubit preparation, read-out, and transfer. The latest theoretical as well as experimental studies of decoherence in these quantum information systems are also provided. Novel demonstrations of complex flying qubit states and first applications of semiconductor-based quantum information devices are given too. Contents: Spin and Charge Qubits; Qubit Control, Readout, and Transfer; Qubit Decoherence; Flying Qubits; Qubit Applications.

✦ Table of Contents

Contents......Page 8
Preface......Page 6
Spin and Charge Qubits......Page 12
1.1. Introduction......Page 14
1.2. Encoding and Manipulation of Three-Spin Coded Qubit States......Page 18
1.3.1. Principles of encoding and manipulating the two-spin qubit......Page 22
1.3.2. Implementation of the two-spin coded qubit......Page 23
1.4. Implementation of the Three-Spin Coded Qubit......Page 31
References......Page 41
Contents......Page 44
2.1.2. Coupled quantum dots......Page 45
2.2. Micro-photoluminescence Experimental Procedure......Page 47
2.3. Symmetric InGaAs/GaAs Lateral Quantum Dot Pairs......Page 48
2.3.1. Sample fabrication and structural characterization......Page 49
2.3.2. Micro-photoluminescence spectra......Page 50
2.3.4. Electric- eld dependent measurements......Page 52
2.4. Asymmetric InP/GaInP Vertical Quantum Dot Pairs......Page 54
2.4.2. Micro-photoluminescence spectra for various spacer thicknesses......Page 56
2.4.3. Time-resolved photoluminescence measurements......Page 58
2.5. Conclusions......Page 59
References......Page 60
Contents......Page 64
3.1. Introduction......Page 65
3.2. Hyper- ne Electron-nuclear Spin Interaction......Page 66
3.3. Nuclear Spin Bi-stability in External Magnetic Fields up to 3T: Experimental Results......Page 69
3.4. Theory of Nuclear Spin Bi-stability in Semiconductor Quantum Dots......Page 80
Acknowledgments......Page 87
References......Page 88
4.1. Introduction......Page 92
4.2. Optical Excitations in Charged Quantum Dots......Page 94
4.3. Optical Electron Spin Pumping......Page 100
4.4. Hyper ne Nuclear-electron Spin Dynamics......Page 109
4.5. Conclusions......Page 117
References......Page 118
Qubit Control, Readout, and Transfer......Page 120
5.1. Introduction......Page 122
5.2. Experiment......Page 125
5.3. Electron g-factor......Page 126
5.4. Creation of Spin Coherence by Spin Initialization......Page 129
5.5. Electron Spin Coherence......Page 140
5.6. Control of Ensemble Spin Precession......Page 150
5.7. Summary......Page 157
References......Page 158
6.1. Introduction......Page 162
6.2. Resonant Scattering from Charge-Tunable QDs......Page 164
6.3. Spin-State Preparation......Page 166
6.4. Spin-State Measurement......Page 169
6.5. Conclusions and Outlook......Page 174
References......Page 175
7. Optical Read-out of Single Carrier Spin in Semiconductor Quantum Dots F. Troiani, I. Wilson-Rae, and C. Tejedor......Page 178
7.1. Quantum Non-demolition Measurement......Page 179
7.2. Level Scheme......Page 180
7.3. Manipulation Scheme......Page 181
7.4. Pulsed Implementation......Page 183
7.5. Continuous Implementation......Page 185
7.6. Conclusions and Outlook......Page 186
References......Page 187
Contents......Page 190
8.1. Introduction......Page 191
8.2. Quantum State Transfer......Page 192
8.3. Dynamics of Quantum State Transfer......Page 194
8.4. Purity and Fidelity of Quantum State Transfer......Page 196
8.5. Dynamics in Electron-Nuclei Coupled System......Page 198
8.6. Bunching in Electron Spin Measurements......Page 199
8.7. Puri cation of Nuclear Spin State......Page 202
8.9. Summary......Page 205
References......Page 206
Qubit Decoherence......Page 210
9.1. Introduction......Page 212
9.2. Description of Samples and Experimental Techniques......Page 214
9.3.1. Exciton ne structure in self organised quantum dots......Page 216
9.3.2. Exciton spin lifetime......Page 218
9.3.3. Exciton spin coherence......Page 220
9.3.4. Exciton/Biexciton spin coherence......Page 222
9.4. Electron Spin Quantum Bits - Dephasing Due to the Hyper ne Interaction......Page 223
9.5. Quantum Bits Based on Collective Nuclear Spin States......Page 230
References......Page 235
10.1. Introduction......Page 240
10.2. Hyper ne Interaction for Electrons in Quantum Dots......Page 241
10.3. Single-Electron Spin Decoherence......Page 243
10.4. Singlet-Triplet Decoherence in a Double Quantum Dot......Page 245
10.5. Nuclear Spin State Narrowing......Page 246
10.6. Spin Decoherence and Relaxation for Heavy Holes......Page 248
10.7. Electric Dipole Spin Resonance for Heavy Holes......Page 252
References......Page 255
Contents......Page 260
11.1. Introduction......Page 261
11.2. Fundamentals of Density-matrix Theory Applied to Solid-state Nanodevices......Page 262
11.3. Fully Operatorial Derivation of the Adiabatic or Markov Limit......Page 264
11.4. Alternative Formulation of the Markov Limit: Deriva- tion of a \Quantum Fermi's Golden Rule"......Page 268
11.5. Derivation of E ective Scattering Superoperators for the Electronic Subsystem......Page 269
11.6. Summary and Conclusions......Page 275
Acknowledgments......Page 276
References......Page 277
Contents......Page 280
12.1. Introduction......Page 281
12.2. Transient Four-Wave Mixing: Background......Page 283
12.3. Heterodyne Detection......Page 288
12.3.1. Heterodyne spectral interferometry......Page 293
12.4. Transient FWM in InGaAs/GaAs Quantum Dot Ensembles......Page 298
12.4.1. Exciton acoustic-phonon interaction: Non Lorentzian homogeneous lineshape......Page 300
12.4.2. Temperature-dependent dephasing: Width of the zero-phonon line......Page 307
12.5.1. Photon-echo formation......Page 313
12.5.2. Rabi oscillations......Page 319
12.6. Summary and Outlook......Page 322
References......Page 324
Flying Qubits......Page 332
Contents......Page 334
13.1. Introduction......Page 335
13.2. Theoretical Background......Page 336
13.3.1. Growth of quantum dot structures......Page 338
13.3.2. Realization of active high-Q micropillar cavities......Page 341
13.4. Experimental Techniques......Page 345
13.5.1. Weak coupling......Page 346
13.5.2. Strong coupling......Page 348
13.6. Photon Antibunching in the Single QD Strong Coupling Regime......Page 351
13.7. Coherent Photonic Coupling of Quantum Dots......Page 355
References......Page 362
14.1. Introduction......Page 366
14.2. Entangled Photon Generation via Atomic and Biexciton Cascades......Page 367
14.3.1. Polarization correlation measurement......Page 371
14.3.2. Violation of Bell's inequality......Page 373
14.3.3. State tomography......Page 374
References......Page 377
15.1. Introduction......Page 380
15.2. Sample and Experimental Design......Page 384
15.3. Correlations for Entangled and Classical Photons......Page 385
15.4. Improving Device Characteristics......Page 389
15.5. Charge Control......Page 390
15.6. Biphoton Interference and Decoherence......Page 392
References......Page 395
Qubit Applications......Page 398
Contents......Page 400
16.1. Introduction......Page 401
16.2.1.1. Growth optimization......Page 402
16.2.1.2. Structural characterization......Page 404
16.2.2. Bimodal dot growth......Page 405
16.3. Single Quantum Dot Spectroscopy......Page 407
16.3.1. Exciton/Biexciton identi cation at 1300nm......Page 408
16.3.1.1. Time resolved PL......Page 410
16.3.2. Measuring g(2)( ) at telecom wavelengths......Page 411
16.3.2.1. Correlation measurements with InGaAs APDs......Page 413
16.3.2.2. Superconducting single photon detectors......Page 414
16.4. Single Quantum Dot Light Emitting Diodes......Page 416
16.4.1.1. Device design......Page 417
16.4.1.2. Current scaling and EL measurements......Page 418
16.4.2.2. Electroluminescence spectroscopy......Page 421
16.4.2.3. Demonstration of single photon emission......Page 424
16.5. Conclusion......Page 425
References......Page 426
Contents......Page 434
17.1. Introduction and Overview......Page 435
17.3. Local Quantum Dot Tuning on a Photonic Crystal Chip......Page 436
17.4. Cavity QED with Quantum Dots in Photonic Crystals......Page 441
17.4.1. Weak coupling regime......Page 443
17.4.2. Strong coupling regime......Page 444
17.5. Generation and Transfer of Single Photons on a Photonic Crystal Chip......Page 447
17.6. Quantum Dot-photonic Crystal Based Quantum Networks......Page 452
17.7. Conclusions and Future Prospects......Page 458
References......Page 459
Contents......Page 464
18.1. Introduction......Page 465
18.2.1. Excitonic interface to the qubus......Page 466
18.2.2. Single-photon-state probe and photon counting de- tection......Page 469
18.2.3. Coherent state probe and homodyne detection......Page 472
18.2.4. System performance......Page 475
18.3.1. Single qubit gate by single broadband optical pulses......Page 477
18.3.2. Two-qubit gates by controlled phase shifts......Page 479
18.3.3. System performance......Page 480
18.4. Hardware......Page 481
18.4.1. Quantum dots in microcavities......Page 482
18.4.2.1. D0:GaAs......Page 484
18.4.2.2. 31P:Si......Page 486
18.4.2.3. 19F:ZnSe......Page 487
References......Page 489
19.1. Introduction......Page 492
19.2. Single Quantum Dots......Page 494
19.3.1. Correlation measurements......Page 495
19.3.2. Micro-photoluminescence......Page 496
19.3.3. InP quantum dots......Page 497
19.4. A Multi-color Photon Source......Page 498
19.5.1. A single-photon add/drop lter......Page 499
19.5.2. Application to quantum key distribution......Page 500
19.6. Deutsch-Jozsa Algorithm with Single Photons from a Single Quantum Dot......Page 501
19.7. Summary......Page 504
References......Page 505
Author Index......Page 508
Subject Index......Page 510