Observation of Josephson Harmonics in Tunnel Junctions
- URL: http://arxiv.org/abs/2302.09192v2
- Date: Tue, 22 Aug 2023 15:55:30 GMT
- Title: Observation of Josephson Harmonics in Tunnel Junctions
- Authors: Dennis Willsch, Dennis Rieger, Patrick Winkel, Madita Willsch,
Christian Dickel, Jonas Krause, Yoichi Ando, Rapha\"el Lescanne, Zaki
Leghtas, Nicholas T. Bronn, Pratiti Deb, Olivia Lanes, Zlatko K. Minev,
Benedikt Dennig, Simon Geisert, Simon G\"unzler, S\"oren Ihssen, Patrick
Paluch, Thomas Reisinger, Roudy Hanna, Jin Hee Bae, Peter Sch\"uffelgen,
Detlev Gr\"utzmacher, Luiza Buimaga-Iarinca, Cristian Morari, Wolfgang
Wernsdorfer, David P. DiVincenzo, Kristel Michielsen, Gianluigi Catelani,
Ioan M. Pop
- Abstract summary: State-of-the-art technologies, including the world's largest quantum processors, employ aluminum oxide (AlO$_x$) tunnel Josephson junctions (JJs) as sources of nonlinearity.
Here we show that the standard C$varphi$R fails to accurately describe the energy spectra of transmon artificial atoms.
By including these in the transmon Hamiltonian, we obtain orders of magnitude better agreement between the computed and measured energy spectra.
- Score: 0.9263754304004778
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: 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$_x$) tunnel Josephson junctions (JJs) as
sources of nonlinearity, assuming an idealized pure $\sin\varphi$ current-phase
relation (C$\varphi$R). However, this celebrated $\sin\varphi$ C$\varphi$R is
only expected to occur in the limit of vanishingly low-transparency channels in
the AlO$_x$ barrier. Here we show that the standard C$\varphi$R 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$_x$ 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.
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