Spin-Orbit Splitting of Andreev States Revealed by Microwave Spectroscopy

Tosi, L.; Metzger, C.; Goffman, M. F.; Urbina, C.; Pothier, H.; Park, Sunghun; Yeyati, A. Levy; Nygård, Jesper; Krogstrup, Peter

doi:10.1103/physrevx.9.011010

Cited by 161 publications

(220 citation statements)

References 51 publications

(87 reference statements)

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“…ABS have been experimentally studied by tunnel or microwave spectroscopy [32][33][34][35][36][37][38][39][40][41][42][43] . Theoretically, one can distinguish between two different regimes: the first one refers to a static phase configuration, i.e.…”

Section: Introductionmentioning

confidence: 99%

Engineering the Floquet spectrum of superconducting multiterminal quantum dots

et al. 2019

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Here we present a theoretical investigation of the Floquet spectrum in multiterminal quantum dot Josephson junctions biased with commensurate voltages. We first draw an analogy between the electronic band theory and superconductivity which enlightens the time-periodic dynamics of the Andreev bound states. We then show that the equivalent of the Wannier-Stark ladders observed in semiconducting superlattices via photocurrent measurements, appears as specific peaks in the finite frequency current fluctuations of superconducting multiterminal quantum dots. In order to probe the Floquet-Wannier-Stark ladder spectra, we have developed an analytical model relying on the sharpness of the resonances. The charge-charge correlation function is obtained as a factorized form of the Floquet wave-function on the dot and the superconducting reservoir populations. We confirm these findings by Keldysh Green's function calculations, in particular regarding the voltage and frequency dependence of the resonance peaks in the current-current correlations. Our results open up a road-map to quantum correlations and coherence in the Floquet dynamics of superconducting devices.

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Section: Introductionmentioning

confidence: 99%

Engineering the Floquet spectrum of superconducting multiterminal quantum dots

et al. 2019

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“…To this end, we use the QD and capacitively-coupled resonator as a probe to characterize a subgap state in the SC without need for transport via leads. Our method is complementary to recent experiments that employed the dispersive response of inductively-coupled resonators to probe the Andreev bound state occupation in galvanically-isolated nanowire Josephson junctions [24,25].…”

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confidence: 86%

Revealing charge-tunneling processes between a quantum dot and a superconducting island through gate sensing

et al. 2019

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We report direct detection of charge-tunneling between a quantum dot and a superconducting island through radio-frequency gate sensing. We are able to resolve spin-dependent quasiparticle tunneling as well as two-particle tunneling involving Cooper pairs. The quantum dot can act as an RF-only sensor to characterize the superconductor addition spectrum, enabling us to access subgap states without transport. Our results provide guidance for future dispersive parity measurements of Majorana modes, which can be realized by detecting the parity-dependent tunneling between dots and islands.

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“…Superconductor nanostructures are the most advanced platforms for quantum computational architectures thanks to the macroscopic coherent wavefunction and the robust protection by the superconducting gap. Recently, various novel qubit concepts like the Andreev (spin) qubits [1][2][3][4][5], Majorana box qubits [6][7][8], braiding with Majorana zero modes in a Majorana or a Shibachain [9][10][11][12][13][14][15][16][17][18] have been put forward or even implemented. All these qubits are based on their associated sub-gap states such as Andreev bound states [19], Majorana zero modes [18,[20][21][22][23][24][25][26] or Shiba states [27][28][29][30].…”

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confidence: 99%

Large spatial extension of the zero-energy Yu–Shiba–Rusinov state in a magnetic field

et al. 2020

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Various promising qubit concepts have been put forward recently based on engineered superconductor (SC) subgap states like Andreev bound states, Majorana zero modes or the Yu-Shiba-Rusinov (Shiba) states. The coupling of these subgap states via a SC strongly depends on their spatial extension and is an essential next step for future quantum technologies. Here we investigate the spatial extension of a Shiba state in a semiconductor quantum dot coupled to a SC for the first time. With detailed transport measurements and numerical renormalization group calculations we find a remarkable more than 50 nm extension of the zero energy Shiba state, much larger than the one observed in very recent scanning tunneling microscopy (STM) measurements. Moreover, we demonstrate that its spatial extension increases substantially in magnetic field.Superconductor nanostructures are the most advanced platforms for quantum computational architectures thanks to the macroscopic coherent wavefunction and the robust protection by the superconducting gap. Recently, various novel qubit concepts like the Andreev (spin) qubits [1-5], Majorana box qubits [6-8], braiding with Majorana zero modes in a Majorana or a Shibachain [9-18] have been put forward or even implemented. All these qubits are based on their associated sub-gap states such as Andreev bound states [19], Majorana zero modes [18,[20][21][22][23][24][25][26] or Shiba states [27][28][29][30]. The Shiba state is formed when a magnetic adatom or its artificial version (quantum dot) is coupled to a superconductor and the localized magnetic moment creates a subgap state by binding an anti-aligned quasiparticle from the superconductor. Depending on the coupling strength between the superconductor and the magnetic moment, the ground state can be either the screened local moment with singlet character or the unscreened doublet states.The coupling of these sub-gap states via a superconductor is an essential next step towards 2-qubit operations or state engineering, e.g. an Andreev molecule [31][32][33] or a Majorana-chain, which consists of series of adatoms or quantum dots interlinked by the superconductor [9][10][11][12][13][14][15][16][17][18]. Obviously, the coupling between such subgap states strongly depends on their spatial extension into the superconductor, so it is required for these localized states to extend as much as possible.So far, the spatial extent and structure of the Shiba states was investigated by STM measurements on mag-netic adatoms deposited on the surface of a superconductor [34][35][36][37] and, interestingly, it revealed that the dimensionality plays a crucial role [36]. In a three dimensional isotropic s-wave superconductor, it was found that the Shiba states decay over a very short distance of the order of ∼ 1 nm [34,35], but extends one order of magnitude further, as far as ∼ 10 nm, if the impurity is placed on the surface of a two-dimensional superconductor [36,38].In this work, we investigate the spatial extension of the Shiba state formed when an artificial ...

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Spin-Orbit Splitting of Andreev States Revealed by Microwave Spectroscopy

Cited by 161 publications

References 51 publications

Engineering the Floquet spectrum of superconducting multiterminal quantum dots

Engineering the Floquet spectrum of superconducting multiterminal quantum dots

Revealing charge-tunneling processes between a quantum dot and a superconducting island through gate sensing

Large spatial extension of the zero-energy Yu–Shiba–Rusinov state in a magnetic field

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