Readout and dynamics of a qubit built on three quantum dots

Łuczak, Jakub; Bułka, Bogdan R.

doi:10.1103/physrevb.90.165427

Cited by 16 publications

(24 citation statements)

References 47 publications

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“…A functioning threespin qubit device capable of quantum computation is demonstrated in a DQD [140,141,142,8] and in a linear TQD [131,4,136,143,137,9,144,145,146,147]. While a triangular shape provides some interesting new features, e.g., chirality [148,149,150,151,152,153,154] and faster qubit operations [2,12], the advantages currently do not seem to outweigh the experimental drawbacks and difficulties. Therefore and since almost all experiments and most theoretical studies use the linear geometry we also mostly stick in this review to the linear geometry and implicitly consider that each TQD is linearly arranged, unless otherwise mentioned.…”

Section: Physical Realization and Measurement Techniquesmentioning

confidence: 99%

Three-electron spin qubits

Russ

Burkard

2017

J. Phys.: Condens. Matter

104

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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Section: Physical Realization and Measurement Techniquesmentioning

confidence: 99%

Three-electron spin qubits

Russ

Burkard

2017

J. Phys.: Condens. Matter

104

117

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“…Recent theoretical studies [31,32,33] showed advantages encoding of the qubit on TQD with a triangular geometry. In this case both the doublet states are equivalent and can be easily controlled by changing the TQD symmetry.…”

Section: Introductionmentioning

confidence: 99%

Landau–Zener transitions in spin qubit encoded in three quantum dots

źUczak

Bułka

2016

Quantum Inf Process

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We study generation and dynamics of an exchange spin qubit encoded in three coherently coupled quantum dots with three electrons. For two geometries of the system, a linear and a triangular one, the creation and coherent control of the qubit states are performed by the Landau-Zener transitions. In the triangular case, both the qubit states are equivalent and can be easily generated for particular symmetries of the system. If one of the dots is smaller than the others, one can observe Rabi oscillations that can be used for coherent manipulation of the qubit states. The linear system is easier to fabricate; however, then the qubit states are not equivalent, making qubit operations more difficult to control.

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“…TTQDs are composed of three coupled quantum dots in a triangle form, with two or three reservoirs connected to them. As the smallest artificial molecule with topological properties, TTQDs received extensive studies, both experimental [9][10][11][12] and theoretical [13][14][15][16][17][18][19][20]. They are prominent candidates for research on various quantum interference effects in the strong correlation regime [18,20].…”

mentioning

confidence: 99%

“…They are prominent candidates for research on various quantum interference effects in the strong correlation regime [18,20]. Remarkably, TTQDs have shown potential applications in quantum computing based on the qubits encoded in chiral spin states [14][15][16]21]. The chiral qubit is embedded in a decoherence-free subspace and is immune to collective noises [22], and thus robust against random charge fluctuations [13].…”

mentioning

confidence: 99%

“…However, the manipulation of chiral qubit or chiral spin state is challenging in general. Existing proposals [13][14][15][16] engage a perpendicular magnetic field to split the degeneracy of left-and right-hand chiral states. Nevertheless, the application of external magnetic field would not be practical for quantum computing, due to its incompatibility with the large-scale integrated circuit.…”

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confidence: 99%

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Bias-induced chiral current and geometrical blockade in triangular triple quantum dot

Wang¹,

Zhu²,

Wei³

et al. 2020

EPL

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We theoretically investigate the quantum transport properties of a triangular triple quantum dot (TTQD) ring connected with two reservoirs by means of analytical derivation and accurate hierarchical-equations-of-motion calculation. A bias-induced chiral current in the absence of magnetic field is firstly demonstrated, which results from that the coupling between spin gauge field and spin current in the nonequilibrium TTQD induces a scalar spin chirality that lifts the chiral degeneracy and thus the time inversion symmetry. The chiral current is proved to oscillate with bias within the Coulomb blockade regime, which opens a possibility to control the chiral spin qubit by use of purely electrical manipulations. Then, a topological blockade of the transport current due to the localization of chiral states is elucidated by spectral function analysis. Finally, as a measurable character, the magnetoelectric susceptibility in our system is found about two orders of magnitude larger than that in a typical magnetoelectric material at low temperature.

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Readout and dynamics of a qubit built on three quantum dots

Cited by 16 publications

References 47 publications

Three-electron spin qubits

Three-electron spin qubits

Landau–Zener transitions in spin qubit encoded in three quantum dots

Bias-induced chiral current and geometrical blockade in triangular triple quantum dot

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