Non-equilibrium quasiparticles in superconducting circuits: photons vs. phonons

Catelani, Gianluigi; Basko, D. M.

doi:10.21468/scipostphys.6.1.013

Cited by 18 publications

(16 citation statements)

References 39 publications

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“…102 At the qubit frequency, quasiparticle excitations present a source of dissipation that enhances energy relaxation and thus reduces T 1 . 103,104 For a phase qubit, 105 the associated energy relaxation rate is given by 1/T 1 = (1 + cos(φ ))…”

Section: [H3] Qubit Measurementsmentioning

confidence: 99%

Engineering high-coherence superconducting qubits

Siddiqi

2021

Nat Rev Mater

168

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Advances in materials science and engineering have played a central role in the development of classical computers, and will undoubtedly be critical in propelling the maturation of quantum information technologies. In approaches to quantum computation based on superconducting circuits, as one goes from bulk materials to functional devices, amorphous insulating films and nonequilibrium excitations-electronic and phononic-are introduced, leading to dissipation and fluctuations that limit the computational power of state-of-the-art qubits and processors. In this Review, the major sources of decoherence in superconducting qubits are identified through an exploration of seminal qubit and resonator experiments. The proposed microscopic mechanisms associated with these imperfections are summarized, and directions for future research are discussed. The trade-offs between simple qubit primitives based on a single Josephson tunnel junction and more complex designs that use additional circuit elements, or new junction modalities, to reduce sensitivity to local noise sources are discussed, particularly in the context of materials optimization strategies for each architecture.

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Section: [H3] Qubit Measurementsmentioning

confidence: 99%

Engineering high-coherence superconducting qubits

Siddiqi

2021

Nat Rev Mater

168

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“…These experiments were able to correlate qubit transitions with changes in the charge-parity of the circuit: a signature of QPs interacting with the qubit [37]. This development has provided a foundation for experiments aiming to mitigate QP-induced dissipation and identify the generation mechanisms of nonequilibrium QPs [38,39].…”

Section: Introductionmentioning

confidence: 97%

Direct Dispersive Monitoring of Charge Parity in Offset-Charge-Sensitive Transmons

et al. 2019

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A striking characteristic of superconducting circuits is that their eigenspectra and intermode coupling strengths are well predicted by simple Hamiltonians representing combinations of quantum circuit elements. Of particular interest is the Cooper-pair-box Hamiltonian used to describe the eigenspectra of transmon qubits, which can depend strongly on the offset-charge difference across the Josephson element. Notably, this offset-charge dependence can also be observed in the dispersive coupling between an ancillary readout mode and a transmon fabricated in the offset-charge-sensitive (OCS) regime. We utilize this effect to achieve direct, high-fidelity dispersive readout of the joint plasmon and charge-parity state of an OCS transmon, which enables efficient detection of charge fluctuations and nonequilibrium-quasiparticle dynamics. Specifically, we show that additional highfrequency filtering can extend the charge-parity lifetime of our device by two orders of magnitude, resulting in a significantly improved energy relaxation time T1 ∼ 200 µs. arXiv:1903.00113v2 [cond-mat.mes-hall]

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“…(15). To the contrary, the resident quasiparticles mechanism [17] leads to Γ 01 Γ 10 , even if their energy distribution is out of equilibrium [27]. Second, the ratio Γ 00 /Γ 10 is large, see Eq.…”

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confidence: 99%

Photon-Assisted Charge-Parity Jumps in a Superconducting Qubit

et al. 2019

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We evaluate the rates of energy and phase relaxation of a superconducting qubit caused by stray photons with energy exceeding the threshold for breaking a Cooper pair. All channels of relaxation within this mechanism are associated with the change in the charge parity of the qubit, enabling the separation of the photon-assisted processes from other contributions to the relaxation rates. Among the signatures of the new mechanism is the same order of rates of the transitions in which a qubit looses or gains energy.

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Non-equilibrium quasiparticles in superconducting circuits: photons vs. phonons

Cited by 18 publications

References 39 publications

Engineering high-coherence superconducting qubits

Engineering high-coherence superconducting qubits

Direct Dispersive Monitoring of Charge Parity in Offset-Charge-Sensitive Transmons

Photon-Assisted Charge-Parity Jumps in a Superconducting Qubit

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