Fermion-parity qubit in a proximitized double quantum dot
Artikel i vetenskaplig tidskrift, 2024

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) interdot tunneling. At weak interdot tunneling, relaxation is suppressed because of disjoint qubit states. However, for strong interdot 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.


Max Geier

Niels Bohr Institute

Massachusetts Institute of Technology (MIT)

Rubén Seoane Souto

Niels Bohr Institute

Lunds universitet

Universidad Autonoma de Madrid (UAM)

CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)

Jens Schulenborg

Niels Bohr Institute

Chalmers, Mikroteknologi och nanovetenskap, Tillämpad kvantfysik

Serwan Asaad

Niels Bohr Institute

Martin Leijnse

Lunds universitet

Niels Bohr Institute

Karsten Flensberg

Niels Bohr Institute

Physical Review Research

26431564 (ISSN)

Vol. 6 2 023281


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