Control of valley dynamics in silicon quantum dots in the presence of an interface step

Boross, Péter; Széchenyi, Gábor; Culcer, Dimitrie; Pályi, András

doi:10.1103/physrevb.94.035438

Cited by 43 publications

(42 citation statements)

References 68 publications

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“…This falls within the range of possible valley relaxation times predicted recently in Ref. [22], where the valley relaxation rate is estimated to be a strong function of the relative location of the quantum dot to a step at the Si-SiO 2 interface.…”

Section: Spin-valley Mixingmentioning

confidence: 52%

Impact of g -factors and valleys on spin qubits in a silicon double quantum dot

et al. 2017

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We define single electron spin qubits in a silicon metal-oxide-semiconductor double quantum dot system. By mapping the qubit resonance frequency as a function of a gate-induced electric field, the spectrum reveals an anticrossing that is consistent with an intervalley spin-orbit coupling. We fit the data from which we extract an intervalley coupling strength of 43 MHz. In addition, we observe a narrow resonance near the primary qubit resonance when we operate the device in the (1,1) charge configuration. The experimental data are consistent with a simulation involving two weakly exchanged-coupled spins with a Zeeman energy difference of 1 MHz, of the same order as the Rabi frequency. We conclude that the narrow resonance is the result of driven transitions between the T − and T + triplet states, using an electron spin resonance signal of frequency located halfway between the resonance frequencies of the two individual spins. The findings presented here offer an alternative method of implementing two-qubit gates, of relevance to the operation of larger-scale spin qubit systems.

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Section: Spin-valley Mixingmentioning

confidence: 52%

Impact of g -factors and valleys on spin qubits in a silicon double quantum dot

et al. 2017

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“…D v 1 v 2 is small yet non negligible in SOI nanowire devices because the v 1 and v 2 wavefunctions show out of phase oscillations along z, and can hence be coupled by the vertical electric field. The field along y does not result in a sizable D v 1 v 2 unless surface roughness disorder couples the motions along z and in the (xy) plane [39,40]. Although C v 1 v 2 is weak in silicon, SOC opens a path for an electrically driven spin resonance |⇓ → |⇑ through a virtual transition from |v 1 , ↓ to |v 2 , ↓ , mediated by the microwave field, and then from |v 2 , ↓ to |v 1 , ↑ , mediated by SOC.…”

Section: Resultsmentioning

confidence: 99%

Electrically driven electron spin resonance mediated by spin–valley–orbit coupling in a silicon quantum dot

Corna¹,

Bourdet²,

Maurand³

et al. 2018

npj Quantum Inf

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The ability to manipulate electron spins with voltage-dependent electric fields is key to the operation of quantum spintronics devices, such as spin-based semiconductor qubits. A natural approach to electrical spin control exploits the spin-orbit coupling (SOC) inherently present in all materials. So far, this approach could not be applied to electrons in silicon, due to their extremely weak SOC. Here we report an experimental realization of electrically driven electron-spin resonance in a silicon-on-insulator (SOI) nanowire quantum dot device. The underlying driving mechanism results from an interplay between SOC and the multi-valley structure of the silicon conduction band, which is enhanced in the investigated nanowire geometry. We present a simple model capturing the essential physics and use tight-binding simulations for a more quantitative analysis. We discuss the relevance of our findings to the development of compact and scalable electron-spin qubits in silicon.

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“…Applying strain raises four of the six valleys in energy such that there exists in silicon QDs an additional two-fold valley degeneracy which has the properties of a pseudo-spin [83]. This two-fold valley degeneracy can be lifted by interfaces in the 2DEG, however, the exact orientation and splitting of the valley depends on atomistic steps of the interface [321,322,323,324,325,326,327,328,329]. This makes the valley splitting very unpredictable, and it is unwanted in qubit implementations in silicon as it boosts up the already large Hilbert space of threespin qubits.…”

Section: Perspectivesmentioning

confidence: 99%

Three-electron spin qubits

Russ

Burkard

2017

J. Phys.: Condens. Matter

101

117

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The goal of this article is to review the progress of three-electron spin qubits from their inception to the state of the art. We direct the main focus towards the exchange-only qubit (Bacon et al 2000 Phys. Rev. Lett. 85 1758-61, DiVincenzo et al 2000 Nature 408 339) and its derived versions, e.g. the resonant exchange (RX) qubit, but we also discuss other qubit implementations using three electron spins. For each three-spin qubit we describe the qubit model, the envisioned physical realization, the implementations of single-qubit operations, as well as the read-out and initialization schemes. Two-qubit gates and decoherence properties are discussed for the RX qubit and the exchange-only qubit, thereby completing the list of requirements for quantum computation for a viable candidate qubit implementation. We start by describing the full system of three electrons in a triple quantum dot, then discuss the charge-stability diagram, restricting ourselves to the relevant subsystem, introduce the qubit states, and discuss important transitions to other charge states (Russ et al 2016 Phys. Rev. B 94 165411). Introducing the various qubit implementations, we begin with the exchange-only qubit (DiVincenzo et al 2000 Nature 408 339, Laird et al 2010 Phys. Rev. B 82 075403), followed by the RX qubit (Medford et al 2013 Phys. Rev. Lett. 111 050501, Taylor et al 2013 Phys. Rev. Lett. 111 050502), the spin-charge qubit (Kyriakidis and Burkard 2007 Phys. Rev. B 75 115324), and the hybrid qubit (Shi et al 2012 Phys. Rev. Lett. 108 140503, Koh et al 2012 Phys. Rev. Lett. 109 250503, Cao et al 2016 Phys. Rev. Lett. 116 086801, Thorgrimsson et al 2016 arXiv:1611.04945). The main focus will be on the exchange-only qubit and its modification, the RX qubit, whose single-qubit operations are realized by driving the qubit at its resonant frequency in the microwave range similar to electron spin resonance. Two different types of two-qubit operations are presented for the exchange-only qubits which can be divided into short-ranged and long-ranged interactions. Both of these interaction types are expected to be necessary in a large-scale quantum computer. The short-ranged interactions use the exchange coupling by placing qubits next to each other and applying exchange-pulses (DiVincenzo et al 2000 Nature 408 339, Fong and Wandzura 2011 Quantum Inf. Comput. 11 1003, Setiawan et al 2014 Phys. Rev. B 89 085314, Zeuch et al 2014 Phys. Rev. B 90 045306, Doherty and Wardrop 2013 Phys. Rev. Lett. 111 050503, Shim and Tahan 2016 Phys. Rev. B 93 121410), while the long-ranged interactions use the photons of a superconducting microwave cavity as a mediator in order to couple two qubits over long distances (Russ and Burkard 2015 Phys. Rev. B 92 205412, Srinivasa et al 2016 Phys. Rev. B 94 205421). The nature of the three-electron qubit states each having the same total spin and total spin in z-direction (same Zeeman energy) provides a natural protection against several sources of noise (DiVincenzo et al 2000 Nature 408 339, Taylor et al 2013 Phys. R...

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Control of valley dynamics in silicon quantum dots in the presence of an interface step

Cited by 43 publications

References 68 publications

Impact of g -factors and valleys on spin qubits in a silicon double quantum dot

Impact of g -factors and valleys on spin qubits in a silicon double quantum dot

Electrically driven electron spin resonance mediated by spin–valley–orbit coupling in a silicon quantum dot

Three-electron spin qubits

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