Realizing singlet-triplet qubits in multivalley Si quantum dots

Abstract

There has been significant progress in the implementation and manipulation of singlet-triplet qubits in GaAs quantum dots. Given the considerably longer spin coherence times measured in Si, considerable interest has been generated recently in Si quantum dots. The physics of these systems is considerably more complex than the physics of GaAs quantum dots owing to the presence of the valley degree of freedom, which constitutes the focus of this work. In this paper we investigate the physics of Si quantum dots and focus on the feasibility of quantum coherent singlet-triplet qubit experiments analogous to those performed in GaAs. This additional degree of freedom greatly increases the complexity of the ground state and gives rise to highly nontrivial and interesting physics in the processes of qubit initialization, coherent manipulation and readout. We discuss the operational definition of a qubit in Si-based quantum dots. We find that in the presence of valley degeneracy a singlet-triplet qubit cannot be constructed, whereas for large valley splitting (>>k_B*T) the experiment is similar to GaAs. We show that experiments on singlet-triplet qubits analogous to those in GaAs would provide a method for estimating the valley coupling in Si. A Zeeman field distinguishes between different initialized states for any valley splitting and provides a tool to determine the size of this splitting.

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• Three-electron spin qubits
• Universal Quantum Computing with Spin and Valley
• Exchange coupling in silicon quantum dots: Theoretical considerations for quantum computation
• Integrated silicon qubit platform with single-spin addressability, exchange control and robust single-shot singlet-triplet readout
• Quantum dot spin qubits in Silicon: Multivalley physics
• Intervalley coupling for interface-bound electrons in silicon: An effective mass study
• Resonant tunnelling features in the transport spectroscopy of quantum dots
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• Valley splitting of single-electron Si MOS quantum dots
• Disorder-induced valley-orbit hybrid states in Si quantum dots
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• Quartet states in two-electron quantum dots in bilayer graphene
• Orbital and valley state spectra of a few-electron silicon quantum dot
• Hyperfine-induced valley mixing and the spin-valley blockade in carbon-based quantum dots
• Spin-valley blockade in carbon nanotube double quantum dots
• Theory of Single Electron Spin Relaxation in Si/SiGe Lateral Coupled Quantum Dots
• Quantum theory of the charge stability diagram of semiconductor double quantum dot systems
• Two-electron dephasing in single Si and GaAs quantum dots
• Spin-Orbit Effects in Carbon-Nanotube Double Quantum Dots
• A quadrupolar exchange-only spin qubit
• Shell Filling and Trigonal Warping in Graphene Quantum Dots
• Long distance coupling of resonant exchange qubits
• Singlet-triplet relaxation in multivalley silicon single quantum dots
• A many-electron tight binding method for the analysis of quantum dot systems
• Theory of Spin Relaxation in Two-Electron Lateral Coupled Si/SiGe Quantum Dots
• Transporting a single-spin qubit through a double quantum dot
• Signatures of atomic-scale structure in the energy dispersion and coherence of a Si quantum-dot qubit
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• Counting Statistics of Single Electron Transport in Bilayer Graphene Quantum Dots
• Phonon-assisted relaxation and decoherence of singlet-triplet qubits in Si/SiGe quantum dots
• Singlet-triplet relaxation in SiGe/Si/SiGe double quantum dots
• Dephasing and Hyperfine Interaction in Carbon Nanotubes Double Quantum Dots: Disordered Case
• Origin of giant valley splitting in silicon quantum wells induced by superlattice barriers
• Voltage controlled exchange energies of a two electron silicon double quantum dot with and without charge defects in the dielectric
• Dephasing and Hyperfine Interaction in Carbon Nanotubes Double Quantum Dots: The Clean Limit
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• Energy spectra of three electrons in Si/SiGe single and vertically coupled double quantum dots
• Spin-dependent inter- and intra-valley electron-phonon scattering in germanium
• Electric control of tunneling energy in graphene double dots
• Dynamical second-order noise sweetspots in resonantly driven spin qubits
• Energy spectra of three electrons in SiGe/Si/SiGe laterally coupled triple quantum dots
• Valley Splitting Correlations Across a Silicon Quantum Well Containing Germanium
• Optimal Control for Electron Shuttling