Hole Spin Qubits in Thin Curved Quantum Wells

Bosco, Stefano; Loss, Daniel

doi:10.1103/physrevapplied.18.044038

Cited by 13 publications

(9 citation statements)

References 93 publications

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“…We compare our analytical results for Ge NWs to numerical calculations of gate-defined one-dimensional channels in a planar heterostructure [25,28] and curved Ge quantum wells (CQW) [31]. Gate-defined channels exhibit a smaller g factor and weaker SOI than in core/shell NWs, but with a similar qualitative behavior of the effective parameters against electric field and strain.…”

Section: Introductionmentioning

confidence: 93%

“…( 7)], the CQW is also subject to a radial strain that resembles the strain in planar heterostructures. Explicitly, the total BP Hamiltonian of CQWs is well approximated by [31]…”

Section: Model Of Nanowirementioning

confidence: 99%

“…( 9), as discussed in Ref. [31]. The longitudinal and radial strain energies can be engineered individually by the radii of the inner and outer shell, R 1 and R 2 , see Eqs.…”

Section: Curved Quantum Wellmentioning

confidence: 99%

“…Semiconducting nanostructures based on holes are emerging as frontrunner candidates to process quantum information because of their large spin-orbit interaction (SOI) [1][2][3][4][5][6] that enables ultrafast and coherent manipulations of spin qubits [7][8][9][10][11][12], strong coupling to resonators [13][14][15], and is an essential ingredient to host exotic particles such as Majorana bound states (MBSs) [16,17]. In hole nanostructures, the SOI is not only surprisingly strong, orders of magnitude larger than in electronic systems [1,18,19], but it is also highly tunable by external electromagnetic fields and it can be engineered by the confinement potential and by strain [20][21][22][23][24][25][26][27][28], resulting in sweet spots where the charge noise plaguing state-of-the-art spin qubits is strongly suppressed [29][30][31]. The qubit coherence is further enhanced by the weak hyperfine noise, another crucial issue for spin-based quantum information processing [32][33][34][35][36][37], that in hole spin qubits encoded in Si and Ge quantum dots (QDs) can be suppressed by isotopic purification [38,39] or by an appropriate QD design …”

Section: Introductionmentioning

confidence: 99%

“…Orbital magnetic field effects play a crucial role in defining the property of hole nanostructures, yielding significant corrections of the g factor and of the effective mass in planar heterostructures [64,65] as well as in NWs [28,31,66]. Orbital effects are also used to study the shape anisotropy in gate defined quantum dots [67].…”

Section: Introductionmentioning

confidence: 99%

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Enhanced orbital magnetic field effects in Ge hole nanowires

et al. 2022

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Hole semiconductor nanowires (NW) are promising platforms to host spin qubits and Majorana bound states for topological qubits because of their strong spin-orbit interactions (SOI). The properties of these systems depend strongly on the design of the cross section and on strain, as well as on external electric and magnetic fields. In this paper, we analyze in detail the dependence of the SOI and g factors on the orbital magnetic field. We focus on magnetic fields aligned along the axis of the NW, where orbital effects are enhanced and result in a renormalization of the effective g factor up to 400%, even at small values of magnetic field. We provide an exact analytical solution for holes in Ge NWs and we derive an effective low-energy model that enables us to investigate the effect of electric fields applied perpendicular to the NW. We also discuss in detail the role of strain, growth direction, and high-energy valence bands in different architectures, including Ge/Si core/shell NWs, gate-defined one-dimensional channels in planar Ge, and curved Ge quantum wells. By comparing NWs with different growth directions, we find that the isotropic approximation is well justified. Curved Ge quantum wells feature large effective g factors and SOI at low electric field, ideal for hosting Majorana bound states. In contrast, at strong electric field, these quantities are independent of the field, making hole spin qubits encoded in curved quantum wells to good approximation not susceptible to charge noise, and significantly boosting their coherence time.

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Section: Introductionmentioning

confidence: 93%

“…( 7)], the CQW is also subject to a radial strain that resembles the strain in planar heterostructures. Explicitly, the total BP Hamiltonian of CQWs is well approximated by [31]…”

Section: Model Of Nanowirementioning

confidence: 99%

“…( 9), as discussed in Ref. [31]. The longitudinal and radial strain energies can be engineered individually by the radii of the inner and outer shell, R 1 and R 2 , see Eqs.…”

Section: Curved Quantum Wellmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhanced orbital magnetic field effects in Ge hole nanowires

et al. 2022

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Spatially correlated classical and quantum noise in driven qubits

Zou,

Bosco,

Loss

2024

npj Quantum Inf

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Correlated noise across multiple qubits poses a significant challenge for achieving scalable and fault-tolerant quantum processors. Despite recent experimental efforts to quantify this noise in various qubit architectures, a comprehensive understanding of its role in qubit dynamics remains elusive. Here, we present an analytical study of the dynamics of driven qubits under spatially correlated noise, including both Markovian and non-Markovian noise. Surprisingly, we find that by operating the qubit system at low temperatures, where correlated quantum noise plays an important role, significant long-lived entanglement between qubits can be generated. Importantly, this generation process can be controlled on-demand by turning the qubit driving on and off. On the other hand, we demonstrate that by operating the system at a higher temperature, the crosstalk between qubits induced by the correlated noise is unexpectedly suppressed. We finally reveal the impact of spatio-temporally correlated 1/f noise on the decoherence rate, and how its temporal correlations restore lost entanglement. Our findings provide critical insights into not only suppressing crosstalk between qubits caused by correlated noise but also in effectively leveraging such noise as a beneficial resource for controlled entanglement generation.

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Modeling of planar germanium hole qubits in electric and magnetic fields

Wang,

Ercan,

Gyure

et al. 2024

npj Quantum Inf

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Hole-based spin qubits in strained planar germanium quantum wells have received considerable attention due to their favorable properties and remarkable experimental progress. The sizeable spin-orbit interaction in this structure allows for efficient qubit operations with electric fields. However, it also couples the qubit to electrical noise. In this work, we perform simulations of a heterostructure hosting these hole spin qubits. We solve the effective mass equations for a realistic heterostructure, provide a set of analytical basis wavefunctions, and compute the effective g-factor of the heavy-hole ground state. Our investigations reveal a strong impact of highly excited light-hole states located outside the quantum well on the g-factor. We find that sweet spots, points of operations that are least susceptible to charge noise, for out-of-plane magnetic fields are shifted to impractically large electric fields. However, for magnetic fields close to in-plane alignment, partial sweet spots at low electric fields are recovered. Furthermore, sweet spots with respect to multiple fluctuating charge traps can be found under certain circumstances for different magnetic field alignments. This work will be helpful in understanding and improving the coherence of germanium hole spin qubits.

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Hole Spin Qubits in Thin Curved Quantum Wells

Cited by 13 publications

References 93 publications

Enhanced orbital magnetic field effects in Ge hole nanowires

Enhanced orbital magnetic field effects in Ge hole nanowires

Spatially correlated classical and quantum noise in driven qubits

Modeling of planar germanium hole qubits in electric and magnetic fields

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