Charge-noise induced dephasing in silicon hole-spin qubits

Malkoc, Ognjen; Stano, Peter; Loss, Daniel

doi:10.48550/arxiv.2201.06181

Cited by 3 publications

(4 citation statements)

References 77 publications

(96 reference statements)

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“…For a detailed analysis of charge noise sources for hole-spin qubits in quantum dots in diamond crystal structure materials such as Si and Ge, see Ref. [79]. A detailed analysis of all noise sources in Ge NWs is of interest but is beyond the scope of the present work.…”

Section: A Qubit Operationmentioning

confidence: 99%

Hole-spin qubits in Ge nanowire quantum dots: Interplay of orbital magnetic field, strain, and growth direction

et al. 2022

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Hole-spin qubits in quasi-one-dimensional structures are a promising platform for quantum information processing because of the strong spin-orbit interaction (SOI). We present analytical results and discuss device designs that optimize the SOI in Ge semiconductors. We show that at the magnetic field values at which qubits are operated, orbital effects of magnetic fields can strongly affect the response of the spin qubit. We study one-dimensional hole systems in Ge under the influence of electric and magnetic fields applied perpendicular to the device. In our theoretical description, we include these effects exactly. The orbital effects lead to a strong renormalization of the g factor. We find a sweet spot of the nanowire (NW) g factor where charge noise is strongly suppressed and present an effective low-energy model that captures the dependence of the SOI on the electromagnetic fields. Moreover, we compare properties of NWs with square and circular cross sections with ones of gate-defined one-dimensional channels in two-dimensional Ge heterostructures. Interestingly, the effective model predicts a flat band ground state for fine-tuned electric and magnetic fields. By considering a quantum dot (QD) harmonically confined by gates, we demonstrate that the NW g-factor sweet spot is retained in the QD. Our calculations reveal that this sweet spot can be designed to coincide with the maximum of the SOI, yielding highly coherent qubits with large Rabi frequencies. We also study the effective g factor of NWs grown along different high-symmetry axes and find that our model derived for isotropic semiconductors is valid for the most relevant growth directions of nonisotropic Ge NWs. Moreover, a NW grown along one of the three main crystallographic axes shows the largest SOI. Our results show that the isotropic approximation is not justified in Ge in all cases.

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Section: A Qubit Operationmentioning

confidence: 99%

Hole-spin qubits in Ge nanowire quantum dots: Interplay of orbital magnetic field, strain, and growth direction

et al. 2022

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“…5a), this enhancement occurs also in long quantum dots. We emphasize that, in contrast to alternative proposals where the lifetime of the qubit is enhanced only at fine-tuned sweet-spots [38][39][40], in thin Ge CQWs the qubit is to good approximation insensitive to charge noise in a wide range of E x , thus enabling highly coherent qubits with a low sensitivity to charge noise, a major issue in state-of-the-art hole spin quantum processors [14].…”

Section: B Decoherence Of the Qubitmentioning

confidence: 92%

“…This architecture not only benefits from the large SOI of hole quantum dots, which can even be reached at lower values of electric field, but it also can be designed to be free of charge noise. In striking contrast to alternative proposals to reduce the charge noise [38][39][40], in CQWs charge noise is suppressed for a wide range of electric fields and not only at fine-tuned points in parameter space, providing a critical technological advantage compared to competing architectures. This enhancement could push spin-based quantum information processing towards new speed and coherence standards.…”

Section: Introductionmentioning

confidence: 88%

Hole spin qubits in thin curved quantum wells

Bosco¹,

Loss²

2022

Preprint

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Hole spin qubits are frontrunner platforms for scalable quantum computers because of their large spin-orbit interaction which enables ultrafast all-electric qubit control at low power. The fastest spin qubits to date are defined in long quantum dots with two tight confinement directions, when the driving field is aligned to the smooth direction. However, in these systems the lifetime of the qubit is strongly limited by charge noise, a major issue in hole qubits. We propose here a different, scalable qubit design, compatible with planar CMOS technology, where the hole is confined in a curved germanium quantum well surrounded by silicon. This design takes full advantage of the strong spin-orbit interaction of holes, and at the same time suppresses charge noise in a wide range of configurations, enabling highly coherent, ultrafast qubit gates. While here we focus on a Si/Ge/Si curved quantum well, our design is also applicable to different semiconductors. Strikingly, these devices allow for ultrafast operations even in short quantum dots by a transversal electric field. This additional driving mechanism relaxes the demanding design constraints, and opens up a new way to reliably interface spin qubits in a single quantum dot to microwave photons. By considering stateof-the-art high-impedance resonators and realistic qubit designs, we estimate interaction strengths of a few hundreds of MHz, largely exceeding the decay rate of spins and photons. Reaching such a strong coupling regime in hole spin qubits will be a significant step towards high-fidelity entangling operations between distant qubits, as well as fast single-shot readout, and will pave the way towards the implementation of a large-scale semiconducting quantum processor.

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“…We now briefly recap the case when there is no spinphonon interaction ( [78]). It has been shown that in the limit of large tilt field W , time evolution of any local operator O is governed by an effective Hamiltonian H s,eff = Y (D + M )Y † such that e iHst Oe −iHst ≈ e iH s,eff t Oe −iH s,eff t , where D is the projection of H s onto the space of M [39,79,80].…”

mentioning

confidence: 99%

Protecting coherence from environment via Stark many-body localization in a Quantum-Dot Simulator

Sarkar¹,

Buča²

2022

Preprint

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Semiconductor platforms are emerging as a promising architecture for storing and processing quantum information e.g., in quantum dot spin qubits. These setups have relatively low nuclear noise, but charge noise coming from many body interactions between the electrons is a major limiting factor with scalability for a useful quantum computer. Here we show how an electric field gradient, readily obtainable with semiconductor quantum dots, can be engineered to induce local quantum coherent dynamical ℓ−bits that have potential to be used as logical qubits. We take into account the full (interacting) electron and phonon dynamics, and analytically, from first principles without any approximation, show that these dynamical ℓ−bits are protected from all sources noise for exponentially long times provided only that the electron-phonon interaction is not completely non-local. Our work opens a new venue for passive quantum error correction and scaling of semiconductor quantum computers.

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Charge-noise induced dephasing in silicon hole-spin qubits

Cited by 3 publications

References 77 publications

Hole-spin qubits in Ge nanowire quantum dots: Interplay of orbital magnetic field, strain, and growth direction

Hole-spin qubits in Ge nanowire quantum dots: Interplay of orbital magnetic field, strain, and growth direction

Hole spin qubits in thin curved quantum wells

Protecting coherence from environment via Stark many-body localization in a Quantum-Dot Simulator

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