5 research outputs found
Observation of Josephson harmonics in tunnel junctions
Approaches to developing large-scale superconducting quantum
processors must cope with the numerous microscopic degrees of freedom
that are ubiquitous in solid-state devices. State-of-the-art superconducting
qubits employ aluminium oxide (AlO) tunnel Josephson junctions as
the sources of nonlinearity necessary to perform quantum operations.
Analyses of these junctions typically assume an idealized, purely sinusoidal
current–phase relation. However, this relation is expected to hold only in the
limit of vanishingly low-transparency channels in the AlO barrier. Here we
show that the standard current–phase relation fails to accurately describe
the energy spectra of transmon artificial atoms across various samples
and laboratories. Instead, a mesoscopic model of tunnelling through
an inhomogeneous AlO barrier predicts percent-level contributions
from higher Josephson harmonics. By including these in the transmon
Hamiltonian, we obtain orders of magnitude better agreement between
the computed and measured energy spectra. The presence and impact of
Josephson harmonics has important implications for developing AlOx-based
quantum technologies including quantum computers and parametric
amplifiers. As an example, we show that engineered Josephson harmonics
can reduce the charge dispersion and associated errors in transmon qubits
by an order of magnitude while preserving their anharmonicity
Observation of Josephson Harmonics in Tunnel Junctions
Superconducting quantum processors have a long road ahead to reach
fault-tolerant quantum computing. One of the most daunting challenges is taming
the numerous microscopic degrees of freedom ubiquitous in solid-state devices.
State-of-the-art technologies, including the world's largest quantum
processors, employ aluminum oxide (AlO) tunnel Josephson junctions (JJs) as
sources of nonlinearity, assuming an idealized pure current-phase
relation (CR). However, this celebrated CR is
only expected to occur in the limit of vanishingly low-transparency channels in
the AlO barrier. Here we show that the standard CR fails to
accurately describe the energy spectra of transmon artificial atoms across
various samples and laboratories. Instead, a mesoscopic model of tunneling
through an inhomogeneous AlO barrier predicts %-level contributions from
higher Josephson harmonics. By including these in the transmon Hamiltonian, we
obtain orders of magnitude better agreement between the computed and measured
energy spectra. The reality of Josephson harmonics transforms qubit design and
prompts a reevaluation of models for quantum gates and readout, parametric
amplification and mixing, Floquet qubits, protected Josephson qubits, etc. As
an example, we show that engineered Josephson harmonics can reduce the charge
dispersion and the associated errors in transmon qubits by an order of
magnitude, while preserving anharmonicity
The Significance of Accelerated Discovery of Advanced Materials to address Societal Challenges
Societal Challenges demand for Advanced Materials, which in turn promise economical potential. Material Acceleration Platforms (MAPs) will decrease their development time and cost. We comment on implications for science, industry and policy concluding with necessary steps towards establishment of MAPs.</p
Observation of Josephson Harmonics in Tunnel Junctions
Superconducting quantum processors have a long road ahead to reach fault-tolerant quantum computing. One of the most daunting challenges is taming the numerous microscopic degrees of freedom ubiquitous in solid-state devices. State-of-the-art technologies, including the world's largest quantum processors, employ aluminum oxide (AlO) tunnel Josephson junctions (JJs) as sources of nonlinearity, assuming an idealized pure current-phase relation (CR). However, this celebrated CR is only expected to occur in the limit of vanishingly low-transparency channels in the AlO barrier. Here we show that the standard CR fails to accurately describe the energy spectra of transmon artificial atoms across various samples and laboratories. Instead, a mesoscopic model of tunneling through an inhomogeneous AlO barrier predicts %-level contributions from higher Josephson harmonics. By including these in the transmon Hamiltonian, we obtain orders of magnitude better agreement between the computed and measured energy spectra. The reality of Josephson harmonics transforms qubit design and prompts a reevaluation of models for quantum gates and readout, parametric amplification and mixing, Floquet qubits, protected Josephson qubits, etc. As an example, we show that engineered Josephson harmonics can reduce the charge dispersion and the associated errors in transmon qubits by an order of magnitude, while preserving anharmonicity
Observation of Josephson Harmonics in Tunnel Junctions
Superconducting quantum processors have a long road ahead to reach fault-tolerant quantum computing. One of the most daunting challenges is taming the numerous microscopic degrees of freedom ubiquitous in solid-state devices. State-of-the-art technologies, including the world's largest quantum processors, employ aluminum oxide (AlO) tunnel Josephson junctions (JJs) as sources of nonlinearity, assuming an idealized pure current-phase relation (CR). However, this celebrated CR is only expected to occur in the limit of vanishingly low-transparency channels in the AlO barrier. Here we show that the standard CR fails to accurately describe the energy spectra of transmon artificial atoms across various samples and laboratories. Instead, a mesoscopic model of tunneling through an inhomogeneous AlO barrier predicts %-level contributions from higher Josephson harmonics. By including these in the transmon Hamiltonian, we obtain orders of magnitude better agreement between the computed and measured energy spectra. The reality of Josephson harmonics transforms qubit design and prompts a reevaluation of models for quantum gates and readout, parametric amplification and mixing, Floquet qubits, protected Josephson qubits, etc. As an example, we show that engineered Josephson harmonics can reduce the charge dispersion and the associated errors in transmon qubits by an order of magnitude, while preserving anharmonicity