Fragility of multi-junction flux qubits against quasiparticle tunneling

Abstract

We study decoherence in superconducting qubits due to quasiparticle tunneling which is enhanced by two known deviations from the equilibrium BCS theory. The first process corresponds to tunneling of an already existing quasiparticle across the junction. The quasiparticle density is increased, e.g., because of an effective quasiparticle doping of the system. The second process is quasiparticle tunneling by breaking of a Cooper pair. This can happen at typical energies of superconducting qubits if there is an extended quasiparticle density inside the gap. We calculate the induced energy decay and pure dephasing rates in typical qubit designs. Assuming the lowest reported value of the non-equilibrium quasiparticle density in Aluminum, we find for the persistent-current flux qubit decay times of the order of recent measurements. Using the typical sub-gap density of states in Niobium we also reproduce observed decay times in the corresponding Niobium flux qubits.

13 pages, 1 figure

References in corpus (15)

• Charge insensitive qubit design derived from the Cooper pair box
• Coupling Superconducting Qubits via a Cavity Bus
• Observation of high coherence in Josephson junction qubits measured in a three-dimensional circuit QED architecture
• Dynamical decoupling and noise spectroscopy with a superconducting flux qubit
• Relaxation and frequency shifts induced by quasiparticles in superconducting qubits
• Loss and decoherence due to stray infrared light in superconducting quantum circuits
• Quasiparticle relaxation of superconducting qubits in the presence of flux
• Kinetics of non-equilibrium quasiparticle tunneling in superconducting charge qubits
• Energy decay and frequency shift of a superconducting qubit from non-equilibrium quasiparticles
• Vanishing quasiparticle density in a hybrid Al/Cu/Al single-electron transistor
• Kinetics of the superconducting charge qubit in the presence of a quasiparticle
• Are pinholes the cause of excess current in superconducting tunnel junctions? A study of Andreev current in highly resistive junctions
• Effect of Quasiparticles Injection on the AC Response of a Superconductor
• Phase-dependent quasiparticle tunneling in Josephson junctions: Measuring the cos-phi term with a superconducting charge qubit
• Charge transport through ultrasmall single and double Josephson junctions coupled to resonant modes of the electromagnetic environment

Cited by in corpus (21)

• The Flux Qubit Revisited to Enhance Coherence and Reproducibility
• Suppressing relaxation in superconducting qubits by quasiparticle pumping
• Decoherence of superconducting qubits caused by quasiparticle tunneling
• Efficient quasiparticle traps with low dissipation through gap engineering
• Parity switching and decoherence by quasiparticles in single-junction transmons
• Dynamic parity recovery in a strongly driven Cooper-pair box
• Optimal configurations for normal-metal traps in transmon qubits
• Cooper-pair transistor as a minimal topological quantum circuit
• Dynamics of parametric fluctuations induced by quasiparticle tunneling in superconducting flux qubits
• Proximity effect in normal-metal quasiparticle traps
• Fractional Josephson effect versus fractional charge in superconducting-normal metal hybrid circuits
• Tunneling and Relaxation of Single Quasiparticles in a Normal-Superconductor-Normal Single Electron Transistor
• Measurement and dephasing of a flux qubit due to heat currents
• Qubit dephasing due to Quasiparticle Tunneling
• Rate of tunneling nonequilibrium quasiparticles in superconducting qubits
• Dephasing due to quasiparticle tunneling in fluxonium qubits: a phenomenological approach
• Correlated transport through junction arrays in the small Josephson energy limit: incoherent Cooper-pairs and hot electrons
• Dissipation by normal-metal traps in transmon qubits
• Charge quantization and detector resolution
• Effects of quasiparticle tunneling in a circuit-QED realization of a strongly driven two-level system
• Low barrier ZrO${}_x$-based Josephson junctions