A single hole spin with enhanced coherence in natural silicon

Piot, N.; B., Brun,; Schmitt, V.; Zihlmann, S.; Michal, V. P.; Apra, A.; Abadillo-Uriel, J. C.; Jehl, X.; Bertrand, B.; Niebojewski, H.; Hutin, L.; Vinet, M.; Urdampilleta, M.; Meunier, T.; Niquet, Y. -M.; Maurand, R.; Franceschi, Silvia

doi:10.48550/arxiv.2201.08637

Cited by 6 publications

(11 citation statements)

References 49 publications

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“…Spin qubits in hole quantum dots are frontrunner candidates to process quantum information and implement large-scale universal quantum computers [1][2][3][4][5][6][7][8]. The key advantages of holes stem from their reduced sensitivity to the noise caused by hyperfine interactions to defects with non-zero nuclear spin [9][10][11][12], and from their strong effective spin-orbit interaction (SOI), which enables ultrafast and all-electric qubit control at low power [13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

Hole spin qubits in thin curved quantum wells

Bosco¹,

Loss²

2022

Preprint

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“…In the thin dot regime L z L x,y , the spin wavefunction has a dominant heavy-hole character [58] along the strong confinement axis taken as z = [001]. The behavior of the g-matrix of such heavy-hole devices has been extensively analyzed with different methods [44-46, 55, 59] reproducing experimental observations [48,56].…”

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confidence: 99%

“…As an example, the sweet lines for transverse coupling (β = 0) enable spin-microwave photon quantum state transfer [70] with fidelities reaching ∼ 97% for realistic noise, typically limited by the photon losses in the resonator (see SM [60]). Single holes have already demonstrated coherence times of the order of tens of µs on such sweet lines [56]. In principle, it is also possible to leverage the longitudinal coupling at finite E y to mediate CZ gates or ZZ interactions between distant qubits [29,30,[34][35][36]60].…”

mentioning

confidence: 99%

Tunable hole spin-photon interaction based on g-matrix modulation

Michal¹,

Abadillo-Uriel²,

Zihlmann³

et al. 2022

Preprint

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We consider a spin circuit-QED device where a superconducting microwave resonator is capacitively coupled to a single hole confined in a semiconductor quantum dot. Thanks to the strong spin-orbit coupling intrinsic to valence-band states, the gyromagnetic g-matrix of the hole can be modulated electrically. This modulation couples the photons in the resonator to the hole spin. We show that the applied gate voltages and the magnetic-field orientation enable a versatile control of the spin-photon interaction, whose character can be switched from fully transverse to fully longitudinal. The longitudinal coupling is actually maximal when the transverse one vanishes and vice-versa. This "reciprocal sweetness" results from geometrical properties of the g-matrix and protects the spin against dephasing or relaxation. We estimate coupling rates reaching ∼ 10 MHz in realistic settings and discuss potential circuit-QED applications harnessing either the transverse or the longitudinal spin-photon interaction. Furthermore, we demonstrate that the g-matrix curvature can be used to achieve parametric longitudinal coupling with enhanced coherence.

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“…Spin qubits in silicon (Si) and germanium (Ge) quantum dots are frontrunner candidates to process quantum information [1][2][3][4][5][6]. Hole spin qubits hold particular promise because of their large and fully tunable spin-orbit interactions (SOI) [7][8][9][10][11][12][13][14][15], enabling ultrafast all-electrical gates at low power [16][17][18][19][20][21][22][23][24][25], and because of their resilience to hyperfine noise even in natural materials [26][27][28][29][30][31]. In current quantum processors, engineering long-range interactions of distant qubits remains a critical challenge.…”

mentioning

confidence: 99%

“…I of [66]. Importantly, the amplitude of γ γ γ L is large and fully tunable by an external electric field E. By simulating long quantum dots in Ge/Si core/shell nanowires [9,21,68,69] and in square Si finFETs [23][24][25], we observe that large coupling strengths |γ γ γ GeO [22,[73][74][75], where the lower symmetry of the cross-section permits to completely turn off the SOI at finite values of E [11] (marked with a triangle). We also examine a quantum dot in strained planar Ge/SiGe heterostructures, an architecture that holds much promise for scaling up quantum computers [17][18][19].…”

mentioning

confidence: 99%

Fully tunable longitudinal spin-photon interactions in Si and Ge quantum dots

Bosco,

Scarlino,

Klinovaja

et al. 2022

Preprint

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Spin qubits in silicon and germanium quantum dots are promising platforms for quantum computing, but entangling spin qubits over micrometer distances remains a critical challenge. Current prototypical architectures maximize transversal interactions between qubits and microwave resonators, where the spin state is flipped by nearly resonant photons. However, these interactions cause back-action on the qubit, that yield unavoidable residual qubit-qubit couplings and significantly affect the gate fidelity. Strikingly, residual couplings vanish when spin-photon interactions are longitudinal and photons couple to the phase of the qubit. We show that large longitudinal interactions emerge naturally in state-of-the-art hole spin qubits. These interactions are fully tunable and can be parametrically modulated by external oscillating electric fields. We propose realistic protocols to measure these interactions and to implement fast and high-fidelity two-qubit entangling gates. These protocols work also at high temperatures, paving the way towards the implementation of large-scale quantum processors.

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A single hole spin with enhanced coherence in natural silicon

Cited by 6 publications

References 49 publications

Hole spin qubits in thin curved quantum wells

Hole spin qubits in thin curved quantum wells

Tunable hole spin-photon interaction based on g-matrix modulation

Fully tunable longitudinal spin-photon interactions in Si and Ge quantum dots

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