Singlet-triplet oscillations in multivalley Si double quantum dots

• URL: http://arxiv.org/abs/2604.24689v1
• Date: Mon, 27 Apr 2026 16:49:48 GMT
• Title: Singlet-triplet oscillations in multivalley Si double quantum dots
• Abstract summary: We present a theoretical description of the process of charge separation and singlet-triplet mixing.<n>We focus on magnetic fields for which the electron spin Zeeman splitting is close to the valley splitting in one of the dots.<n>We give a detailed description of singlet-triplet dynamics near these spin-valley resonances and compare the results of calculations with measurements on double quantum dots in two distinct Si/SiGe heterostructures.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Charge separation from the $(4,0)$ to the $(3,1)$ state in a Si/SiGe double quantum dot is commonly used for initialization of spin qubits and Pauli-spin-blockade readout. It was used in recent experiments involving creation of the $(3,1)$ singlet, and subsequent shuttling of one of the electrons. We present a theoretical description of the process of charge separation and singlet-triplet mixing, arriving at expressions for the singlet return probability that take into account experimentally observed finite probabilities of the creation of singlets with various patterns of valley occupations. In our analysis we focus on magnetic fields for which the electron spin Zeeman splitting is close to the valley splitting in one of the dots, when the spin-valley coupling causes a strong renormalization of the frequency of oscillations of singlet return probability. The latter effect has been recently used to perform valley splitting mapping by shuttling of one quantum dot to various locations with respect to the other. We give a detailed description of singlet-triplet dynamics near these spin-valley resonances and compare the results of calculations with measurements on double quantum dots in two distinct Si/SiGe heterostructures. Comparison of theory with experiments in which the presence of a few valley occupation patterns is visible, gives insight into the valley dependence of $g$-factors in these structures, providing support for a recently proposed theoretical model of this dependence. We also discuss how dephasing of singlet return probability oscillations near the spin-valley resonances is affected by valley splitting fluctuations caused by electric field noise.

Related papers

• Non-perturbative theory of valley splitting in Si qubits from variational wave function: periodic effects of shear strain and asymptotic freedom in the wiggle-well potential [0.0]
  Valley splitting sets the energy scale at which spin and valley degrees of freedom hybridize in silicon quantum-well qubits.<n>We develop an analytical framework for treating non-perturbative effects of shear strain and wiggle-well potentials.
  arXiv  Detail & Related papers  (2026-09-08T14:56:28Z)
• Valley-Enabled Intrinsic Dresselhaus Spin-Orbit Coupling in Silicon [0.0]
  We show a symmetry-based theory of spin-orbit-valley coupling in silicon.<n>We derive the symmetry-allowed spin-valley couplings generated by magnetic-field gradients.<n>These results establish valley symmetry as a fundamental ingredient in the spin-orbit physics of silicon.
  arXiv  Detail & Related papers  (2026-08-30T13:25:34Z)
• On trace invariance and energy-dependent entanglement in muon decay [45.88028371034407]
  We revisit a proposed correction to the muon magnetic anomaly measurement.<n>We compare it with energy-binned scans reported by the Fermilab $g-2$ collaboration.
  arXiv  Detail & Related papers  (2026-08-19T12:06:54Z)
• Quantum theory of a three-photon Kerr parametric oscillator [75.2200279238806]
  We investigate the quantum properties of a nonlinear Kerr oscillator driven by a three-photon pump.<n>We show that the squeezing can be enhanced, suppressed, or even reversed, leading to a squeezing-to-anti-squeezing transition.
  arXiv  Detail & Related papers  (2026-05-20T11:14:54Z)
• Multirate characterization of relaxation mechanisms for two nonequivalent nuclear spins 1/2 in a liquid using maximally entangled pseudo-pure quantum states [41.99844472131922]
  Multirate characterization of spin responses in nuclear magnetic resonance (NMR) is a promising approach to fingerprinting complex molecules.<n>We present experimental and theoretical investigations simultaneously accessing 8 relaxation rates describing the density matrix of two adjacent nonequivalent nuclear spins.
  arXiv  Detail & Related papers  (2026-04-29T21:42:37Z)
• Symmetry-protected topology and deconfined solitons in a multi-link $\mathbb{Z}_2$ gauge theory [45.88028371034407]
  We study a $mathbbZ$ lattice gauge theory defined on a multi-graph with links that can be visualized as great circles of a spherical shell.<n>We show that this leads to state-dependent tunneling amplitudes underlying a phenomenon analogous to the Peierls instability.<n>By performining a detailed analysis based on matrix product states, we prove that charge deconfinement emerges as a consequence of charge-fractionalization.
  arXiv  Detail & Related papers  (2026-03-02T22:59:25Z)
• Evidence for Multimodal Superfluidity of Neutrons [33.960965008651684]
  We show that the condensate consists of coexisting s-wave pairs, p-wave pairs in entangled double pair combinations, and quartets composed of bound states of two s-wave pairs.<n>We identify multimodal superfluidity as a general feature of single-flavor spin-1/2 fermionic systems with attractive s-wave and p-wave interactions.
  arXiv  Detail & Related papers  (2026-02-19T18:36:50Z)
• Harnessing Chiral Spin States in Molecular Nanomagnets for Quantum Technologies [44.1973928137492]
  We show that chiral qubits naturally suppress always-on interactions that can not be switched off in weakly coupled qubits.<n>Our findings establish spin chirality engineering as a promising strategy for mitigating always-on interaction in entangling two chiral qubits in molecular quantum technologies.
  arXiv  Detail & Related papers  (2025-01-21T08:23:12Z)
• Theory of Valley Splitting in Si/SiGe Spin-Qubits: Interplay of Strain, Resonances and Random Alloy Disorder [0.0]
  A critical challenge in strained Si/SiGe quantum wells is the existence of two nearly degenerate valley states at the conduction band minimum.<n>We develop a comprehensive envelope-function theory augmented by an empirical nonlocal pseudopotential model to incorporate the effects of alloy disorder, strain, and non-trivial resonances.
  arXiv  Detail & Related papers  (2024-12-29T23:43:41Z)
• Robust spectral $\pi$ pairing in the random-field Floquet quantum Ising model [44.84660857803376]
  We study level pairings in the many-body spectrum of the random-field Floquet quantum Ising model. The robustness of $pi$ pairings against longitudinal disorder may be useful for quantum information processing.
  arXiv  Detail & Related papers  (2024-01-09T20:37:48Z)
• Cooperative quantum tunneling of the magnetization in Fe-doped Li$_3$N [0.0]
  The spin-reversal in dilute Li$$$(Li$_1-x$Fe$_x$)N with $x 1$ % is dominated by resonant quantum tunneling of spatially well-separated states. We report on the effect of finite couplings between those states that give rise to cooperative, simultaneous quantum tunneling of two spins.
  arXiv  Detail & Related papers  (2023-10-27T14:59:42Z)
• Liouvillian gap and single spin-flip dynamics in the dissipative Fermi-Hubbard model [0.0]
  We analyze the Fermi-Hubbard model on a $d$-dimensional hypercubic lattice with two-body loss. We also investigate the dynamics of a ferromagnetic initial state with a single spin flip.
  arXiv  Detail & Related papers  (2022-09-08T12:03:45Z)
• Valleytronic full configuration-interaction approach: An application to the excitation spectra of Si double-dot qubits [0.0]
  We study the influence of strong electron-electron interactions and Wigner-molecule (WM) formation on the spectra of Si qubits. We present results for both the $E_rm ST E_V$ and $E_rm ST E_V$ cases.
  arXiv  Detail & Related papers  (2022-08-11T03:55:52Z)
• Dispersive readout of molecular spin qudits [68.8204255655161]
  We study the physics of a magnetic molecule described by a "giant" spin with multiple $d > 2$ spin states. We derive an expression for the output modes in the dispersive regime of operation. We find that the measurement of the cavity transmission allows to uniquely determine the spin state of the qudits.
  arXiv  Detail & Related papers  (2021-09-29T18:00:09Z)
• Zitterbewegung and Klein-tunneling phenomena for transient quantum waves [77.34726150561087]
  We show that the Zitterbewegung effect manifests itself as a series of quantum beats of the particle density in the long-time limit. We also find a time-domain where the particle density of the point source is governed by the propagation of a main wavefront. The relative positions of these wavefronts are used to investigate the time-delay of quantum waves in the Klein-tunneling regime.
  arXiv  Detail & Related papers  (2020-03-09T21:27:02Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.