Spin Lifetime and Charge Noise in Hot Silicon Quantum Dot Qubits

Petit, Luca; Boter, Jelmer; Eenink, H. G. J.; Droulers, G.; Tagliaferri, Marco; Li, R.; Franke, David; Singh, Kanwal Jit; Clarke, James Stanier; Schouten, R. N.; Dobrovitski, V. V.; Vandersypen, L. M. K.; Veldhorst, Menno

doi:10.1103/physrevlett.121.076801

Cited by 107 publications

(104 citation statements)

References 28 publications

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“…As shown in Figure 4, however, data from individual dots show strong deviations from a 1/f spectrum and linear temperature dependence. Non-linear temperature dependence and anomalous frequency dependence of the charge noise have also previously been observed in semiconductor quantum dots [9,38,39]. In the following, we describe how a non-uniform distribution of TLSs can give rise to this behavior.…”

supporting

confidence: 53%

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mentioning

confidence: 99%

“…Although silicon qubits largely avoid nuclear spin noise, charge noise in the semiconductor still limits both single-and multi-qubit gate fidelities. Moreover, charge noise levels appear to be similar in different silicon devices and materials [4,9,[11][12][13][14][15][16]. Because noise mitigation strategies such as device engineering, dynamical decoupling [17,18], and dynamically corrected gates [19] rely on a detailed understanding of the noise, a thorough characterization of charge noise is essential.…”

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confidence: 99%

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Low-frequency charge noise in Si/SiGe quantum dots

et al. 2019

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Electron spins in silicon have long coherence times [1][2][3][4][5][6] and are a promising qubit platform [7,8]. However, electric field noise in semiconductors poses a challenge for most single-and multi-qubit operations in quantum-dot spin qubits [4,9,10]. Here, we investigate the dependence of lowfrequency charge noise spectra on temperature and aluminum-oxide gate dielectric thickness in Si/SiGe quantum dots with overlapping gates. We find that charge noise increases with aluminum oxide thickness. We also find strong dot-to-dot variations in the temperature dependence of the noise magnitude and spectrum. These findings suggest that each quantum dot experiences noise caused by a distinct ensemble of two-level systems, each of which has a non-uniform distribution of thermal activation energies. Taken together, our results suggest that charge noise in Si/SiGe quantum dots originates at least in part from a non-uniform distribution of two-level systems near the surface of the semiconductor.

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confidence: 53%

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mentioning

confidence: 99%

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confidence: 99%

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Low-frequency charge noise in Si/SiGe quantum dots

et al. 2019

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“…Temperature has the strongest impact on T 1 , which scales as T −5 between 0.5 and 1.0 K. This could be interpreted as a Raman process involving intervalley piezophonons stemming from the oxide layerif the spin-lattice relaxation was dominated by Si deformation potential phonons, the temperature power law should be stronger, as discussed in Ref. [29]. T Hahn 2 and T * 2 display a weaker dependence on temperature.…”

mentioning

confidence: 86%

Operation of a silicon quantum processor unit cell above one kelvin

Yang

Leon

Hwang

et al. 2020

Nature

298

235

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Quantum computers are expected to outperform conventional computers for a range of important problems, from molecular simulation to search algorithms, once they can be scaled up to large numbers of quantum bits (qubits), typically millions [1][2][3]. For most solid-state qubit technologies, e.g. those using superconducting circuits or semiconductor spins, scaling poses a significant challenge as every additional qubit increases the heat generated, while the cooling power of dilution refrigerators is severely limited at their operating temperature below 100 mK [4][5][6]. Here we demonstrate operation of a scalable silicon quantum processor unit cell, comprising two qubits confined to quantum dots (QDs) at ∼1.5 Kelvin. We achieve this by isolating the QDs from the electron reservoir, initialising and reading the qubits solely via tunnelling of electrons between the two QDs [7-9]. We coherently control the qubits using electrically-driven spin resonance (EDSR) [10,11] in isotopically enriched silicon 28 Si [12], attaining single-qubit gate fidelities of 98.6% and coherence time T * 2 = 2 µs during 'hot' operation, comparable to those of spin qubits in natural silicon at millikelvin temperatures [13][14][15][16]. Furthermore, we show that the unit cell can be operated at magnetic fields as low as 0.1 T, corresponding to a qubit control frequency of 3.5 GHz, where the qubit energy is well below the thermal energy. The unit cell constitutes the core building block of a full-scale silicon quantum computer, and satisfies layout constraints required by error correction architectures [8,17]. Our work indicates that a spin-based quantum computer could be operated at elevated temperatures in a simple pumped 4 He system, offering orders of magnitude higher cooling power than dilution refrigerators, potentially enabling classical control electronics to be integrated with the qubit array [18,19].Electrostatically gated QDs in Si/SiGe or Si/SiO 2 heterostructures are prime candidates for spin-based quantum computing due to their long coherence times, high control fidelities, and industrial manufacturability [13,14,[20][21][22][23]. In large scale quantum processors the qubits will be arranged in either 1D chains [17] or 2D arrays [3] to enable quantum error correction schemes. For architectures relying on exchange coupling for twoqubit operation [15,16,24,25], the QDs are expected to be densely packed. Until now, two-qubit QD systems have been tunnel-coupled to a nearby charge reservoir that has typically been used for initialisation and readout using spin-to-charge conversion [26]. Here we demonstrate an isolated double QD system that requires no tunnel-coupled reservoir [7-9] to perform full two-qubit initialisation, control and readout -thus realising the elementary unit cell of a scalable quantum processor (see Figure 1h).

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“…Empirically, semiconductor qubits are often limited by 1/f charge noise [30,31,32], which in turn leads to a power spectral density of exchange fluctuations S J (f ) = A 2 J /f . Therefore we will focus on modeling the expected exchange noise amplitude A J ; in Appendix E we discuss the connection between this quantity and γ for different experiments.…”

Section: Tqd Qubit Operation and Key Quantities For Spin-photon Couplingmentioning

confidence: 99%

Resonant exchange operation in triple-quantum-dot qubits for spin–photon transduction

Pan

Keating²,

Gyure³

et al. 2020

Quantum Sci. Technol.

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Triple quantum dots (TQDs) are promising semiconductor spin qubits because of their all-electrical control via fast, tunable exchange interactions and immunity to global magnetic fluctuations. These qubits couple to photons in the resonant exchange (RX) regime, when exchange is simultaneously active on both qubit axes. However, most theoretical work has been based on phenomenological Fermi-Hubbard models, which may not fully capture the complexity of the qubit spin-charge states in this regime. Here we investigate exchange in Si/SiGe and GaAs TQDs using full configuration interaction (FCI) calculations which better describe practical device operation. We show that high exchange operation in general, and the RX regime in particular, can differ significantly from simple models, presenting new challenges and opportunities for spin-photon coupling. We highlight the impact of device electrostatics and effective mass on exchange and identify a new operating point (XRX) where strong spin-photon coupling is most likely to occur in Si/SiGe TQDs. Based on our numerical results, we analyze the feasibility of a remote entanglement cavity iSWAP protocol and discuss design pathways for improving fidelity. Our analysis provides insight into the requirements for TQD spin-photon transduction and demonstrates more generally the necessity of accurate modeling of exchange in spin qubits. ‡ Present address:

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Spin Lifetime and Charge Noise in Hot Silicon Quantum Dot Qubits

Cited by 107 publications

References 28 publications

Low-frequency charge noise in Si/SiGe quantum dots

Low-frequency charge noise in Si/SiGe quantum dots

Operation of a silicon quantum processor unit cell above one kelvin

Resonant exchange operation in triple-quantum-dot qubits for spin–photon transduction

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