Quantum dot spin qubits in Silicon: Multivalley physics

Abstract

Research on Si quantum dot spin qubits is motivated by the long spin coherence times measured in Si, yet the orbital spectrum of Si dots is increased as a result of the valley degree of freedom. The valley degeneracy may be lifted by the interface potential, which gives rise to a valley-orbit coupling, but the latter depends on the detailed structure of the interface and is generally unknown a priori. These facts motivate us to provide an extensive study of spin qubits in Si double quantum dots, accounting fully for the valley degree of freedom and assuming no prior knowledge of the valley-orbit coupling. For single-spin qubits we analyze the spectrum of a multivalley double quantum dot, discuss the initialization of one qubit, identify the conditions for the lowest energy two-electron states to be a singlet and a triplet well separated from other states, and determine analytical expressions for the exchange splitting. For singlet-triplet qubits we analyze the single-dot spectrum and initialization process, the double-dot spectrum, singlet-triplet mixing in an inhomogeneous magnetic field and the peculiarities of spin blockade in multivalley qubits. We review briefly the hyperfine interaction in Si and discuss its role in spin blockade in natural Si, including intravalley and intervalley effects. We study the evolution of the double-dot spectrum as a function of magnetic field. We address briefly the situation in which the valley-orbit coupling is different in each dot due to interface roughness. We propose a new experiment for measuring the valley splitting in a single quantum dot. We discuss the possibility of devising other types of qubits in Si QDs, and the size of the intervaley coupling due to the Coulomb interaction.

22 pages, 7 figures

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Cited by in corpus (65)

• Silicon Quantum Electronics
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• Gate Defined Quantum Confinement in Suspended Bilayer Graphene
• Pauli Spin Blockade in a Highly Tunable Silicon Double Quantum Dot
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• Valley-based noise-resistant quantum computation using Si quantum dots
• Electron spin resonance and spin-valley physics in a silicon double quantum dot
• Spin-orbit coupling and operation of multi-valley spin qubits
• Three-electron spin qubits
• Integrated silicon qubit platform with single-spin addressability, exchange control and robust single-shot singlet-triplet readout
• Intervalley coupling by quantum dot confinement potentials in monolayer transition metal dichalcogenides
• Dispersively detected Pauli Spin-Blockade in a Silicon Nanowire Field-Effect Transistor
• Intervalley coupling for interface-bound electrons in silicon: An effective mass study
• Fast and high-fidelity state preparation and measurement in triple-quantum-dot spin qubits
• Hubbard model description of silicon spin qubits: charge stability diagram and tunnel coupling in Si double quantum dots
• Electron g-factor of valley states in realistic silicon quantum dots
• Magnetic field dependence of Pauli spin blockade: a window into the sources of spin relaxation in silicon quantum dots
• Orbital and valley state spectra of a few-electron silicon quantum dot
• Detuning Axis Pulsed Spectroscopy of Valley-Orbital States in Si/SiGe Quantum Dots
• Control of valley dynamics in silicon quantum dots in the presence of an interface step
• Hybrid spin and valley quantum computing with singlet-triplet qubits
• Theory of Single Electron Spin Relaxation in Si/SiGe Lateral Coupled Quantum Dots
• Network architecture for a topological quantum computer in silicon
• Modelling semiconductor spin qubits and their charge noise environment for quantum gate fidelity estimation
• Quantum theory of the charge stability diagram of semiconductor double quantum dot systems
• A quadrupolar exchange-only spin qubit
• Theory of spin blockade, charge ratchet effect, and thermoelectrical behavior in serially coupled quantum-dot system
• Simulated coherent electron shuttling in silicon quantum dots
• Long distance coupling of resonant exchange qubits
• Effects of Interface Steps on the Valley Orbit coupling in a Si/SiGe quantum dot
• Lifetime enhanced transport in silicon due to spin and valley blockade
• Do micromagnets expose spin qubits to charge and Johnson noise?
• Probing the Spatial Variation of the Inter-Valley Tunnel Coupling in a Silicon Triple Quantum Dot
• Resonant Exchange Operation in Triple-Quantum-Dot Qubits for Spin-Photon Transduction
• Theory of Spin Relaxation in Two-Electron Lateral Coupled Si/SiGe Quantum Dots
• Impact of valley phase and splitting on readout of silicon spin qubits
• Transporting a single-spin qubit through a double quantum dot
• Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling
• Modulated longitudinal gates on encoded spin-qubits via curvature couplings to a superconducting cavity
• Valley Phase and Voltage Control of Coherent Manipulation in Si Quantum Dots
• Pauli spin blockade in CMOS double quantum dot devices
• Phonon-assisted relaxation and decoherence of singlet-triplet qubits in Si/SiGe quantum dots
• Electrical operation of hole spin qubits in planar MOS silicon quantum dots
• Singlet-triplet relaxation in SiGe/Si/SiGe double quantum dots
• Dephasing and Hyperfine Interaction in Carbon Nanotubes Double Quantum Dots: Disordered Case
• Electric dipole spin resonance in systems with a valley dependent g-factor
• Dephasing and Hyperfine Interaction in Carbon Nanotubes Double Quantum Dots: The Clean Limit
• Coulomb interaction and valley-orbit coupling in Si quantum dots
• A low-disorder Metal-Oxide-Silicon double quantum dot
• Understanding disorder in Silicon quantum computing platforms: Scattering mechanisms in Si/SiGe quantum wells
• Measurement of tunnel coupling in a Si double quantum dot based on charge sensing
• Optimal control of a cavity-mediated iSWAP gate between silicon spin qubits
• Theory of valley-resolved spectroscopy of a Si triple quantum dot coupled to a microwave resonator
• Valleytronic full configuration-interaction approach: An application to the excitation spectra of Si double-dot qubits
• Energy spectra of three electrons in Si/SiGe single and vertically coupled double quantum dots
• Qubit-environment entanglement outside of pure decoherence: hyperfine interaction
• Direct measurement of electron intervalley relaxation in a Si/SiGe quantum dot
• Charge noise suppression in capacitively coupled singlet-triplet spin qubits under magnetic field
• Optimisation of electrically-driven multi-donor quantum dot qubits
• Energy spectra of three electrons in SiGe/Si/SiGe laterally coupled triple quantum dots
• Proposal for a cavity-induced measurement of the exchange coupling in quantum dots
• Rapid adiabatic gating for capacitively coupled quantum dot hybrid qubits without barrier control
• Impact of the valley orbit coupling on exchange gate for spin qubits in silicon quantum dots
• Interplay of Pauli blockade with electron-photon coupling in quantum dots
• Inter- and intra-band Coulomb interactions between holes in silicon nanostructures