High-temperature operation of a silicon qubit

Ono, Ken; Mori, Takahiro; Moriyama, Satoshi

doi:10.1038/s41598-018-36476-z

Cited by 43 publications

(46 citation statements)

References 49 publications

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“…In addition, deep-level defects have been observed in Si as potential spin qubits. 46,47 For a localized defect in Si with the same spin states as a NV center, for example, a tin vacancy, 47 we predict T 2 in the bulk and in a 4-nm slab to be 1.15 and 1.25 ms, respectively, for 4.7% of 29 Si, values that are about 35-30% larger than the corresponding ones in C diamond with 1.1% of 13 C. This points at The tables shows the parameters α (ms) and β. The constant α is equal to the T 2 value at 1% 13 C concentration, while β, which is the slope in Fig.…”

Section: Effect Of Reduced Dimensionalitymentioning

confidence: 99%

Spin coherence in two-dimensional materials

Seo

Galli

2019

npj Comput Mater

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Spin defects in semiconducting solids are promising platforms for the realization of quantum bits. At low temperature and in the presence of a large magnetic field, the central spin decoherence is mainly due to the fluctuating magnetic field induced by nuclear spin flip-flop transitions. Using spin Hamiltonians and a cluster expansion method, we investigate the electron spin coherence of defects in two-dimensional (2D) materials, including delta-doped diamond layers, thin Si films, MoS 2 , and h-BN. We show that isotopic purification is much more effective in 2D than in three-dimensional materials, leading to an exceptionally long spin coherence time of more than 30 ms in an isotopically pure monolayer of MoS 2 .npj Computational Materials (2019) 5:44 ; https://doi.

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Section: Effect Of Reduced Dimensionalitymentioning

confidence: 99%

Spin coherence in two-dimensional materials

Seo

Galli

2019

npj Comput Mater

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“…Prior studies have examined the relaxation of Si-MOS QD spin qubits at temperatures of 1.1 K [29] and coherence times of ensembles of Si-MOS QDs up to 10 K [30]. The coherence times of single deeplevel impurities in silicon at 10 K [31] and ensembles of donor electron spins in silicon up to 20 K [32,33] were also examined. However, coherence times and gate fidelities of these qubits have not been investigated as yet.…”

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confidence: 99%

Operation of a silicon quantum processor unit cell above one kelvin

Yang

Leon

Hwang

et al. 2020

Nature

284

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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“…Significant stress/strains will lead to the formation of unintentional dots that can be detrimental to the operation of the intentional dots. There are various methods for avoiding unintentional dots in a quantum dot system [10] and reducing strain from room temperature down to < 1 K [11]. Moreover, the modulation of the conduction band due to strain can also be compensated to a limited degree through variation of voltages applied to the gates [12,13].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Strain Effect between Aluminum and Palladium Gated MOS Quantum Dot Systems

2020

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As nano-scale metal-oxide-semiconductor devices are cooled to temperatures below 1 K, detrimental effects due to unintentional dots become apparent. The reproducibility of the location of these unintentional dots suggests that there are other mechanisms in play, such as mechanical strains in the semiconductor introduced by metallic gates. Here, we investigate the formation of strain-induced dots on aluminum and palladium gated metal oxide semiconductor (MOS) quantum devices using COMSOL Multiphysics. Simulation results show that the strain effect on the electrochemical potential of the system can be minimized by replacing aluminum with palladium as the gate material and increasing the thickness of the gate oxide.

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High-temperature operation of a silicon qubit

Cited by 43 publications

References 49 publications

Spin coherence in two-dimensional materials

Spin coherence in two-dimensional materials

Operation of a silicon quantum processor unit cell above one kelvin

Comparison of Strain Effect between Aluminum and Palladium Gated MOS Quantum Dot Systems

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