Spectral response of Josephson junctions with low-energy quasiparticles

Keselman, Anna; Murthy, Chaitanya; Heck, Bernard van; Bauer, Bela

doi:10.21468/scipostphys.7.4.050

Cited by 34 publications

(40 citation statements)

References 86 publications

(116 reference statements)

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“…The prediction of E M from device parameters is difficult as E M depends sensitively on the potential in the junction. While E M is expected to increase as the junction barrier is lowered, its value is likely limited by the presence of additional transport channels within the subgap spectrum of the junction [25,30].…”

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confidence: 99%

Destructive Little-Parks Effect in a Full-Shell Nanowire-Based Transmon

et al. 2020

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A semiconductor transmon with an epitaxial Al shell fully surrounding an InAs nanowire core is investigated in the low E J =E C regime. Little-Parks oscillations as a function of flux along the hybrid wire axis are destructive, creating lobes of reentrant superconductivity separated by a metallic state at a half quantum of applied flux. In the first lobe, phase winding around the shell can induce topological superconductivity in the core. Coherent qubit operation is observed in both the zeroth and first lobes. Splitting of parity bands by coherent single-electron coupling across the junction is not resolved beyond line broadening, placing a bound on Majorana coupling, E M =h < 10 MHz, much smaller than the Josephson coupling E J =h ∼ 4.7 GHz.

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confidence: 99%

Destructive Little-Parks Effect in a Full-Shell Nanowire-Based Transmon

et al. 2020

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“…In the δ → 0 limit (dotted curve), both parity sectors have minima at zero energy and the periodicity becomes e [43,44]. Furthermore, MBSs coherently mix parities around n g = 0.25 and n g = 0.75 [9,10,16]. In the transmon limit with δ = 0, Fig.…”

Section: Resultsmentioning

confidence: 94%

“…This relevant regime has hitherto remained unexplored, even at the level of the effective models in Refs. [9,10,16], which focus on the opposite E M /E C 1 regime where the large charging energy prevents changes in the GS parity [37]. This would require much larger E C (which is detrimental since it induces charge dispersion) or very small Majorana couplings E M E J .…”

Section: Resultsmentioning

confidence: 99%

“…Recent experimental efforts are pushing the standard operation limits in order to have JJs compatible with electrical gating and high magnetic fields. This compatibility is a crucial step to reach a regime relevant for microwave (MW) readout of topological qubits based on Majorana bound states (MBSs) [5][6][7][8][9][10][11][12][13][14][15][16]. Various options include semiconductors [17][18][19][20][21][22][23] and van der Waals heterostructures [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

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Majorana oscillations and parity crossings in semiconductor nanowire-based transmon qubits

Ávila

Prada

San-José

et al. 2020

Phys. Rev. Research

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We show that the microwave (MW) spectra in semiconductor-nanowire-based transmon qubits provide a strong signature of the presence of Majorana bound states in the junction. This occurs as an external magnetic field tunes the wire into the topological regime and the energy splitting of the emergent Majorana modes oscillates around zero energy owing to their wave function spatial overlap in finite-length wires. In particular, we discuss how these Majorana oscillations, and the concomitant fermion parity switches in the ground state of the junction, result in distinct spectroscopic features-in the form of an intermittent visibility of absorption lines-that strongly deviate from standard transmon behavior. In contrast, nonoscillating zero modes, such as topologically trivial Andreev bound states resulting from sufficiently smooth potentials, exhibit an overall standard transmon response. These differences in the MW response could help determine whether the junction contains topological Majoranas or not.

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“…where local density terms remain unchanged:n P; j,σβB; j,σβ † B; j,σ =n P; j,σ . Exploiting this representation, one of the authors studied the charge-degeneracy points of topologically superconducting islands coupled to normal leads [67][68][69][70].…”

Section: Hubbard Model With Pair Creation and Annihilationmentioning

confidence: 99%

Efficient and flexible approach to simulate low-dimensional quantum lattice models with large local Hilbert spaces

2021

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Quantum lattice models with large local Hilbert spaces emerge across various fields in quantum many-body physics. Problems such as the interplay between fermions and phonons, the BCS-BEC crossover of interacting bosons, or decoherence in quantum simulators have been extensively studied both theoretically and experimentally. In recent years, tensor network methods have become one of the most successful tools to treat such lattice systems numerically. Nevertheless, systems with large local Hilbert spaces remain challenging. Here, we introduce a mapping that allows to construct artificial U(1)U(1) symmetries for any type of lattice model. Exploiting the generated symmetries, numerical expenses that are related to the local degrees of freedom decrease significantly. This allows for an efficient treatment of systems with large local dimensions. Further exploring this mapping, we reveal an intimate connection between the Schmidt values of the corresponding matrixproductstate representation and the singlesite reduced density matrix. Our findings motivate an intuitive physical picture of the truncations occurring in typical algorithms and we give bounds on the numerical complexity in comparison to standard methods that do not exploit such artificial symmetries. We demonstrate this new mapping, provide an implementation recipe for an existing code, and perform example calculations for the Holstein model at half filling. We studied systems with a very large number of lattice sites up to L=501L=501 while accounting for N_{\rm ph}=63 phonons per site with high precision in the CDW phase.

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Spectral response of Josephson junctions with low-energy quasiparticles

Cited by 34 publications

References 86 publications

Destructive Little-Parks Effect in a Full-Shell Nanowire-Based Transmon

Destructive Little-Parks Effect in a Full-Shell Nanowire-Based Transmon

Majorana oscillations and parity crossings in semiconductor nanowire-based transmon qubits

Efficient and flexible approach to simulate low-dimensional quantum lattice models with large local Hilbert spaces

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