Dynamics of spin-flip photon-assisted tunneling

Braakman, Floris; Danon, Jeroen; Schreiber, Lars R.; Wegscheider, Werner; Vandersypen, L. M. K.

doi:10.1103/physrevb.89.075417

Cited by 15 publications

(22 citation statements)

References 18 publications

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“…Even though H so is simpler compared to that in Ref. 16 , it can give good agreement with the basic trends observed in the experiments 4,12,28 . The Hamiltonian of the leads describes non interacting electrons and is given by…”

Section: Introductionsupporting

confidence: 77%

Transport spectroscopy of a spin-orbit-coupled spin to a quantum dot

Giavaras

Nori

2016

Phys. Rev. B

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Electron spins in quantum dots can interact with impurity spins located in an adjacent region. This interaction may be controllable using external electric fields and it can involve an appreciable spin-orbit interaction (SOI) part affecting the expected operation of the dot spins. In this work we propose a method to quantify the interaction between a dot spin and a nearby spin by calculating the electrical current through the dot. We demonstrate some interesting regimes where the SOI can be detected, and find regimes of negative differential conductance which are sensitive to the strength of the SOI. The present study could be useful for spin-orbit qubits formed in quantum dot devices.

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Section: Introductionsupporting

confidence: 77%

Transport spectroscopy of a spin-orbit-coupled spin to a quantum dot

Giavaras

Nori

2016

Phys. Rev. B

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“…Since the exchange interaction is limited to adjacent QDs, other long-range interactions have to be considered to overcome this technical difficulty allowing for a two-dimensional array of qubits which are spatially separated [236]. There are several proposals for the achievement of such an interaction, e.g., tunneling mediated by a superconductor [237,238], coupling though surface acoustic waves [239,240,241,242,243,244], ferromagnets [245], superexchange mediated by an additional QD [246,247,92,248], spatial adiabatic passage [249,222,250], photon assisted tunneling [251,252,253], and quantum Hall edge states [254,243]. The most practical ideas (up to date) seem to be Coulomb-based dipoledipole coupling [10,255,256] and cavity quantum electrodynamics (cQED) mediated coupling [137,16,187,211,105,17,257,258,106] which both use the electric dipole moment of the qubit, whereas in the second approach the interaction range is elongated by the use of a cavity as a mediator [97,98,16,17,3].…”

Section: Long-ranged Two-qubit Gatesmentioning

confidence: 99%

Three-electron spin qubits

Russ

Burkard

2017

J. Phys.: Condens. Matter

102

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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“…The picture becomes even richer when considering transitions in which not only the spin state but also the orbital quantum number changes. Such phenomena are common in optically active dots [20], but have been observed also in electrostatically defined (double) quantum dots in the form of relaxation from spin triplet to spin singlet states [21,22] and spin-flip photon-assisted tunneling [23,24]. However, that work is all in semiconductor quantum dots with no valley degree of freedom, and the degree to which valleys -often treated as weakly coupled to each other and orbital states-couple to each other to enable microwave-driven transitions that change spin has not been explored.…”

mentioning

confidence: 95%

Dressed photon-orbital states in a quantum dot: Intervalley spin resonance

Scarlino¹,

Kawakami²,

Jullien³

et al. 2017

Phys. Rev. B

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The valley degree of freedom is intrinsic to spin qubits in Si/SiGe quantum dots. It has been viewed alternately as a hazard, especially when the lowest valley-orbit splitting is small compared to the thermal energy, or as an asset, most prominently in proposals to use the valley degree of freedom itself as a qubit. Here we present experiments in which microwave electric field driving induces transitions between both valley-orbit and spin states. We show that this system is highly nonlinear and can be understood through the use of dressed photon-orbital states, enabling a unified understanding of the six microwave resonance lines we observe. Some of these resonances are intervalley spin transitions that arise from a non-adiabatic process in which both the valley and the spin degree of freedom are excited simultaneously. For these transitions, involving a change in valleyorbit state, we find a tenfold increase in sensitivity to electric fields and electrical noise compared to pure spin transitions, strongly reducing the phase coherence when changes in valley-orbit index are incurred. In contrast to this non-adiabtaic transition, the pure spin transitions, whether arising from harmonic or subharmonic generation, are shown to be adiabatic in the orbital sector. The nonlinearity of the system is most strikingly manifest in the observation of a dynamical anti-crossing between a spin-flip, inter-valley transition and a three-photon transition enabled by the strong nonlinearity we find in this seemly simple system.A spin-1/2 particle is the canonical two-level quantum system. Its energy level structure is extremely simple, consisting of just the spin-up and spin-down levels. Therefore, when performing spectroscopy on an elementary spin-1/2 particle such as an electron spin, only a single resonance is expected corresponding to the energy separation between the two levels.Recent measurements have shown that the spectroscopic response of a single electron spin in a quantum dot can be much more complex than this simple picture suggests. This is particularly true when using electricdipole spin resonance, where an oscillating electric field couples to the spin via spin-orbit coupling [1]. First, due to non-linearities in the response to oscillating driving fields, subharmonics can be observed [2][3][4][5][6][7], and the nonlinear response can even be exploited for driving coherent spin rotations [8]. Second, due to spin-orbit coupling, the exact electron spin resonance frequency in a given magnetic field depends on the orbital the electron occupies [9]. In silicon or germanium quantum dots, the conduction band valley is an additional degree of freedom [10][11][12][13][14], and the electron spin resonance frequency should depend on the valley state as well [14][15][16][17][18][19]. As a result, when valley or orbital energy splittings are comparable to or smaller than the thermal energy, thermal occupation of the respective levels leads to the observation of multiple closely spaced spin resonance frequencies [17].The picture ...

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Dynamics of spin-flip photon-assisted tunneling

Cited by 15 publications

References 18 publications

Transport spectroscopy of a spin-orbit-coupled spin to a quantum dot

Transport spectroscopy of a spin-orbit-coupled spin to a quantum dot

Three-electron spin qubits

Dressed photon-orbital states in a quantum dot: Intervalley spin resonance

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