Spin qubit manipulation of acceptor bound states in group IV quantum wells

Abadillo-Uriel, J. C.; Calderón, M. J.

doi:10.1088/1367-2630/aa695f

Cited by 10 publications

(11 citation statements)

References 49 publications

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“…The projection of the spin-3/2 onto the axis perpendicular to the interface,ẑ, is m J = ±3/2 for the heavy holes (HH) and m J = ±1/2 for the light holes (LH). Tensile strain gives the qubit a LH character 29,53 , ensuring a strong Zeeman interaction with an in-plane magnetic field. 54 The tetrahedral symmetry of the acceptors gives rise to a linear coupling to the electric field of the form…”

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confidence: 99%

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Entanglement control and magic angles for acceptor qubits in Si

Abadillo-Uriel

Salfi

et al. 2018

Applied Physics Letters

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Full electrical control of quantum bits could enable fast, low-power, scalable quantum computation. Although electric dipoles are highly attractive to couple spin qubits electrically over long distances, mechanisms identified to control two-qubit couplings do not permit single-qubit operations while two-qubit couplings are off. Here we identify a mechanism to modulate electrical coupling of spin qubits that overcomes this drawback for hole spin qubits in acceptors,that is based on the electrical tuning of the direction of the spin-dependent electric dipole by a gate. In this way, inter-qubit coupling can be turned off electrically by tuning to a "magic angle" of vanishing electric dipole-dipole interactions, while retaining the ability to manipulate the individual qubits. This effect stems from the interplay of the T d symmetry of the acceptor state in the Si lattice with the magnetic field orientation, and the spin-3/2 characteristic of hole systems. Magnetic field direction also allows to greatly suppress spin relaxation by phonons that limit single qubit performance, while retaining sweet spots where the qubits are insensitive to charge noise. Our findings can be directly applied to state-of-the-art acceptor based architectures, for which we propose suitable protocols to practically achieve full electrical tunability of entanglement and the realization of a decoherence-free subspace.

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confidence: 99%

“…56, however in this work we consider a magnetic field B with an arbitrary in-plane orientation characterised by an angle φ. In the basis {3/2, 1/2, −1/2, −3/2}, the effective Hamiltonian is 29,53…”

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confidence: 99%

Entanglement control and magic angles for acceptor qubits in Si

Abadillo-Uriel

Salfi

et al. 2018

Applied Physics Letters

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Section: Introductionmentioning

confidence: 99%

“…Since the oscillation occurs on atomic lengthscales, control of donor-donor interactions often requires precise placement of dopant atoms, which can be problematic 6 . Acceptorbased qubits [13][14][15][16][17][18][19][20] lack such multivalley complications, so variation in the acceptor-acceptor interaction occurs on the much longer lengthscale of the effective Bohr radius (tens to hundreds of angstroms). However, while donors are well modeled as effective hydrogen atoms and donor pairs as effective hydrogen molecules, acceptors are somewhat more complex, due to a degenerate valence band maximum and the effects of spin-orbit coupling, as described by the Luttinger Hamiltonian 21,22 .…”

Section: Introductionmentioning

confidence: 99%

Quadrupolar interactions between acceptor pairs in p -doped semiconductors

2020

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We consider the interaction between acceptor pairs in doped semiconductors in the limit of large inter-acceptor separation relevant for low doping densities. Modeling individual acceptors via the spherical model of Baldereschi and Lipari, we calculate matrix elements of the quadrupole tensor between the four degenerate ground states and show that the acceptor has a nonzero quadrupole moment. As a result, the dominant contribution to the large-separation acceptor-acceptor interaction comes from direct (charge-density) terms rather than exchange terms. The quadrupole is the leading nonzero moment, so the electric quadrupole-quadrupole interaction dominates for large separation. We calculate the matrix elements of the quadrupole-quadrupole interaction Hamiltonian in a product-state basis and diagonalize, obtaining a closed-form expression for the energies and degeneracies of the sixteen-state energy spectrum. All dependence on material parameters enters via an overall prefactor, resulting in surprisingly simple and universal results. This simplicity can be traced to a mathematical happenstance, the nontrivial vanishing of a particular Wigner 6-j symbol, 2 2 2 3 2 3 2 3 2 = 0. Results are relevant to the control of two-qubit interactions in quantum computing implementations based on acceptor spins, as well as calculations of the thermodynamic properties of insulating p-type semiconductors.

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“…For this reason, amongst others, there have been a number of recent proposals for acceptor-based qubits [22][23][24][25][26][27][28][29] . For acceptors, there aren't multiple valleys, so exchange is monotonic, and only involves the larger impurity (Bohr) radius.…”

Section: Introductionmentioning

confidence: 99%

Heitler-London model for acceptor-acceptor interactions in doped semiconductors

2017

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The interactions between acceptors in semiconductors are often treated in qualitatively the same manner as those between donors. Acceptor wave functions are taken to be approximately hydrogenic and the standard hydrogen molecule Heitler-London model is used to describe acceptor-acceptor interactions. But due to valence band degeneracy and spin-orbit coupling, acceptor states can be far more complex than those of hydrogen atoms, which brings into question the validity of this approximation. To address this issue, we develop an acceptor-acceptor Heitler-London model using single-acceptor wave functions of the form proposed by Baldereschi and Lipari, which more accurately capture the physics of the acceptor states. We calculate the resulting acceptor-pair energy levels and find, in contrast to the two-level singlet-triplet splitting of the hydrogen molecule, a rich ten-level energy spectrum. Our results, computed as a function of inter-acceptor distance and spin-orbit coupling strength, suggest that acceptor-acceptor interactions can be qualitatively different from donor-donor interactions, and should therefore be relevant to the control of twoqubit interactions in acceptor-based qubit implementations, as well as the magnetic properties of a variety of p-doped semiconductor systems. Further insight is drawn by fitting numerical results to closed-form energy-level expressions obtained via an acceptor-acceptor Hubbard model. FIG. 1: Hydrogen molecule Heitler-London submatrix structure for both the H and S matrices. Shaded elements are nonzero. Equal elements share the same label.

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Spin qubit manipulation of acceptor bound states in group IV quantum wells

Cited by 10 publications

References 49 publications

Entanglement control and magic angles for acceptor qubits in Si

Entanglement control and magic angles for acceptor qubits in Si

Quadrupolar interactions between acceptor pairs in p -doped semiconductors

Heitler-London model for acceptor-acceptor interactions in doped semiconductors

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