Spin-EPR-pair separation by conveyor-mode single electron shuttling in Si/SiGe

Struck, Tom; Volmer, Mats; Visser, Lino; Offermann, Tobias; Xue, Ran; Tu, Jhih-Sian; Trellenkamp, Stefan; Cywiński, Łukasz; Bluhm, Hendrik; Schreiber, Lars R.

doi:10.1038/s41467-024-45583-7

Cited by 13 publications

(6 citation statements)

References 37 publications

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“…By including echo pulses we can extend the effective length scale to l coh = 49 μm. These results compare favorably to effective lengths obtained in silicon 15 , 27 – 29 . However, we note that, in general, extrapolating the performance of shuttling experiments over few sites to predict the performance of practical shuttling links requires caution.…”

Section: Discussionsupporting

confidence: 79%

“…For example, if the noise is local, echo pulses may prove less effective. However, in that case, motional narrowing 22 , 25 , 29 , 45 – 47 may facilitate the shuttling.…”

Section: Discussionmentioning

confidence: 99%

“…The potential of shuttling-based quantum buses has stimulated research on shuttling electron charge 19 – 21 and spin 15 , 22 – 29 . While nuclear spin noise prevents high-fidelity qubit operation in gallium arsenide, demonstrations of coherent transfer of individual electron spins through quantum dots are encouraging 22 – 26 .…”

Section: Introductionmentioning

confidence: 99%

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Coherent spin qubit shuttling through germanium quantum dots

van Riggelen-Doelman,

Wang,

de Snoo

et al. 2024

Nat Commun

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Quantum links can interconnect qubit registers and are therefore essential in networked quantum computing. Semiconductor quantum dot qubits have seen significant progress in the high-fidelity operation of small qubit registers but establishing a compelling quantum link remains a challenge. Here, we show that a spin qubit can be shuttled through multiple quantum dots while preserving its quantum information. Remarkably, we achieve these results using hole spin qubits in germanium, despite the presence of strong spin-orbit interaction. In a minimal quantum dot chain, we accomplish the shuttling of spin basis states over effective lengths beyond 300 microns and demonstrate the coherent shuttling of superposition states over effective lengths corresponding to 9 microns, which we can extend to 49 microns by incorporating dynamical decoupling. These findings indicate qubit shuttling as an effective approach to route qubits within registers and to establish quantum links between registers.

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Section: Discussionsupporting

confidence: 79%

“…For example, if the noise is local, echo pulses may prove less effective. However, in that case, motional narrowing 22 , 25 , 29 , 45 – 47 may facilitate the shuttling.…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coherent spin qubit shuttling through germanium quantum dots

van Riggelen-Doelman,

Wang,

de Snoo

et al. 2024

Nat Commun

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show abstract

“…In this manuscript, we present the SpinBus architecture, which leverages the conveyor-mode shuttling device named Quantum Bus (QuBus) as used in demonstration experiments 27 , 28 , 32 to connect qubits (Fig. 1 a).…”

Section: Resultsmentioning

confidence: 99%

“… 27 ), spin-coherent shuttling with a maximum velocity of 2.8 m/s across an accumulated distance of at least 2.4 μm has been demonstrated. The spin dephasing time of the shuttled electron spin is enhanced by motional narrowing, which contributes even in the absence of 29 Si isotopes due to remaining 73 Ge isotopes, and leads to a fidelity of ~99% for the transfer of a spin quantum state over a nominal shuttling distance of 560 nm 32 . In addition, motional narrowing is also expected for charge noise, albeit with a longer correlation length set roughly by the distance of the noise source from the channel 29 .…”

Section: Introductionmentioning

confidence: 99%

The SpinBus architecture for scaling spin qubits with electron shuttling

Künne,

Willmes,

Oberländer

et al. 2024

Nat Commun

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Quantum processor architectures must enable scaling to large qubit numbers while providing two-dimensional qubit connectivity and exquisite operation fidelities. For microwave-controlled semiconductor spin qubits, dense arrays have made considerable progress, but are still limited in size by wiring fan-out and exhibit significant crosstalk between qubits. To overcome these limitations, we introduce the SpinBus architecture, which uses electron shuttling to connect qubits and features low operating frequencies and enhanced qubit coherence. Device simulations for all relevant operations in the Si/SiGe platform validate the feasibility with established semiconductor patterning technology and operation fidelities exceeding 99.9%. Control using room temperature instruments can plausibly support at least 144 qubits, but much larger numbers are conceivable with cryogenic control circuits. Building on the theoretical feasibility of high-fidelity spin-coherent electron shuttling as key enabling factor, the SpinBus architecture may be the basis for a spin-based quantum processor that meets the scalability requirements for practical quantum computing.

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Atomistic Compositional Details and Their Importance for Spin Qubits in Isotope‐Purified Silicon Quantum Wells

Klos,

Tröger,

Keutgen

et al. 2024

Advanced Science

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Understanding crystal characteristics down to the atomistic level increasingly emerges as a crucial insight for creating solid state platforms for qubits with reproducible and homogeneous properties. Here, isotope concentration depth profiles in a SiGe/28Si/SiGe heterostructure are analyzed with atom probe tomography (APT) and time‐of‐flight secondary‐ion mass spectrometry down to their respective limits of isotope concentrations and depth resolution. Spin‐echo dephasing times and valley energy splittings EVS around have been observed for single spin qubits in this quantum well (QW) heterostructure, pointing toward the suppression of qubit decoherence through hyperfine interaction with crystal host nuclear spins or via scattering between valley states. The concentration of nuclear spin‐carrying 29Si is 50 ± 20ppm in the 28Si QW. The resolution limits of APT allow to uncover that both the SiGe/28Si and the 28Si/SiGe interfaces of the QW are shaped by epitaxial growth front segregation signatures on a few monolayer scale. A subsequent thermal treatment, representative of the thermal budget experienced by the heterostructure during qubit device processing, broadens the top SiGe/28Si QW interface by about two monolayers, while the width of the bottom 28Si/SiGe interface remains unchanged. Using a tight‐binding model including SiGe alloy disorder, these experimental results suggest that the combination of the slightly thermally broadened top interface and of a minimal Ge concentration of % in the QW, resulting from segregation, is instrumental for the observed large . Minimal Ge additions <1%, which get more likely in thin QWs, will hence support high EVS without compromising coherence times. At the same time, taking thermal treatments during device processing as well as the occurrence of crystal growth characteristics into account seems important for the design of reproducible qubit properties.

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Spin-EPR-pair separation by conveyor-mode single electron shuttling in Si/SiGe

Cited by 13 publications

References 37 publications

Coherent spin qubit shuttling through germanium quantum dots

Coherent spin qubit shuttling through germanium quantum dots

The SpinBus architecture for scaling spin qubits with electron shuttling

Atomistic Compositional Details and Their Importance for Spin Qubits in Isotope‐Purified Silicon Quantum Wells

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