Nuclear spin induced decoherence of a quantum dot in Si confined at a SiGe interface: Decoherence dependence on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mn>73</mml:mn></mml:msup></mml:math>Ge

Witzel, Wayne; Rahman, Rajib; Carroll, Malcolm S.

doi:10.1103/physrevb.85.205312

Cited by 18 publications

(13 citation statements)

References 30 publications

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“…At the same time, it opens a new dephasing channel for electric noise, due to the static longitudinal gradient magnetic field of the micromagnet, competing with the magnetic noise. To fully exploit the potential of magnetic noise minimization through isotope enrichment in 28 Si/SiGe, two experimental questions thus become relevant for devices with integrated static magnetic field gradients: Firstly, to what extent electronic noise impacts the spin qubit dephasing compared to magnetic noise 18 and, secondly, which role the natural SiGe potential wall barriers play for dephasing, since the hyperfine interaction of bulk Ge exceeds the one of bulk Si by a factor of approximately 100 19,20 .…”

Section: Introductionmentioning

confidence: 99%

Low-frequency spin qubit energy splitting noise in highly purified 28Si/SiGe

et al. 2020

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We identify the dominant source for low-frequency spin qubit splitting noise in a highly isotopically-purified silicon device with an embedded nanomagnet and a spin echo decay time T echo 2 = 128 µs. The power spectral density (PSD) of the charge noise explains both, the clear transition from a 1/f 2-to a 1/f-dependence of the splitting noise PSD as well as the experimental observation of a decreasing time-ensemble spin dephasing time, from T Ã 2 % 20 µs, with increasing measurement time over several hours. Despite their strong hyperfine contact interaction, the few 73 Ge nuclei overlapping with the quantum dot in the barrier do not limit T Ã 2 , likely because their dynamics is frozen on a few hours measurement scale. We conclude that charge noise and the design of the gradient magnetic field are the key to further improve the qubit fidelity in isotopically purified 28 Si/SiGe.

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Section: Introductionmentioning

confidence: 99%

Low-frequency spin qubit energy splitting noise in highly purified 28Si/SiGe

et al. 2020

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“…2(f). When the interaction with the excited valley is weak, we expect the dephasing to be dominated by the hyperfine interaction with residual 29 Si [7,[26][27][28][29][30]. As the interaction strength increases, the coupling to nearby electric fields will be enhanced, increasing sensitivity to charge noise.…”

Section: Resultsmentioning

confidence: 99%

A silicon singlet-triplet qubit driven by spin-valley coupling

Jock,

Jacobson,

Rudolph

et al. 2021

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Spin-orbit effects, inherent to electrons confined in quantum dots at a silicon heterointerface, provide a means to control electron spin qubits without the added complexity of on-chip, nanofabricated micromagnets or nearby coplanar striplines. Here, we demonstrate a novel singlet-triplet qubit operating mode that can drive qubit evolution at frequencies in excess of 200 MHz. This approach offers a means to electrically turn on and off fast control, while providing high logic gate orthogonality and long qubit dephasing times. We utilize this operational mode for dynamical decoupling experiments to probe the charge noise power spectrum in a silicon metal-oxide-semiconductor double quantum dot. In addition, we assess qubit frequency drift over longer timescales to capture low-frequency noise. We present the charge noise power spectral density up to 3 MHz, which exhibits a 1/f α dependence, with α ∼ 0.7, over 9 orders of magnitude in noise frequency.

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“…Germanium was the original material for transistors, and is now being developed for the latest semiconductor electronics [1]. Recently, it has become a key material for spintronics [2][3][4] and quantum computing [5][6][7] devices. Compared to silicon, donor electrons in Ge have higher mobility (∼ 3 times) [1], larger wavefunctions (6.5 nm compared to 2.5 nm), [8,9], stronger spin-orbit coupling [10], and highly anisotropic conduction band valleys [6].…”

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confidence: 99%

Electron Spin Coherence of Shallow Donors in Natural and Isotopically Enriched Germanium

et al. 2015

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Germanium is a widely used material for electronic and optoelectronic devices and recently it has become an important material for spintronics and quantum computing applications. Donor spins in silicon have been shown to support very long coherence times (T2) when the host material is isotopically enriched to remove any magnetic nuclei. Germanium also has non-magnetic isotopes so it is expected to support long T2s while offering some new properties. Compared to Si, Ge has a strong spin-orbit coupling, large electron wavefunction, high mobility, and highly anisotropic conduction band valleys which will all give rise to new physics. In this Letter, the first pulsed electron spin resonance (ESR) measurements of T2 and the spin-lattice relaxation (T1) times for 75 As and 31 P donors in natural and isotopically enriched germanium are presented. We compare samples with various levels of isotopic enrichment and find that spectral diffusion due to 73 Ge nuclear spins limits the coherence in samples with significant amounts of 73 Ge. For the most highly enriched samples, we find that T1 limits T2 to T2 = 2T1. We report an anisotropy in T1 and the ensemble linewidths for magnetic fields oriented along different crystal axes but do not resolve any angular dependence to the spectral-diffusion-limited T2 in samples with 73 Ge.

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Nuclear spin induced decoherence of a quantum dot in Si confined at a SiGe interface: Decoherence dependence on73Ge

Cited by 18 publications

References 30 publications

Low-frequency spin qubit energy splitting noise in highly purified 28Si/SiGe

Low-frequency spin qubit energy splitting noise in highly purified 28Si/SiGe

A silicon singlet-triplet qubit driven by spin-valley coupling

Electron Spin Coherence of Shallow Donors in Natural and Isotopically Enriched Germanium

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