Fermion-parity qubit in a proximitized double quantum dot

Abstract

Bound states in quantum dots coupled to superconductors can be in a coherent superposition of states with different electron number but with the same fermion parity. Electrostatic gating can tune this superposition to a sweet spot, where the quantum dot has the same mean electric charge independent of its electron-number parity. Here, we propose to encode quantum information in the local fermion parity of two tunnel-coupled quantum dots embedded in a Josephson junction. At the sweet spot, the qubit states have zero charge dipole moment. This protects the qubit from dephasing due to charge noise acting on the potential of each dot, as well as fluctuations of the (weak) inter-dot tunneling. At weak inter-dot tunneling, relaxation is suppressed because of disjoint qubit states. On the other hand, for strong inter-dot tunneling the system is protected against noise affecting each quantum dot separately (energy level noise, dot-superconductor tunneling fluctuations, and hyperfine interactions). Finally, we describe initialization and readout as well as single-qubit and two-qubit gates by pulsing gate voltages.

20 pages, 8 figures; V2: published version

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Cited by in corpus (13)

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• Interplay between Majorana and Shiba states in a minimal Kitaev chain coupled to a superconductor
• Impurity states in altermagnetic superconductors
• Flux-tunable Josephson Effect in a Four-Terminal Junction
• Subgap states in semiconductor-superconductor devices for quantum technologies: Andreev qubits and minimal Majorana chains
• YSR Bond Qubit in a Double Quantum Dot with cQED Operation
• Spin-Exchange Induced Spillover on Poor Man's Majoranas in Minimal Kitaev Chains
• Properties of multiterminal superconducting nanostructure with double quantum dot
• Properties and prevalence of false poor man's Majoranas in two- and three-site artificial Kitaev chains
• Scalable Effective Models for Superconducting Nanostructures: Applications to Double, Triple, and Quadruple Quantum Dots
• Revisiting the Poor Man's Majoranas: The Spin-Exchange Induced Spillover Effect
• Transient triplet blockade in Andreev junction