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A graphene-based Josephson junction incorporated in a superconducting circuit forms a voltage-tunable transmon qubit that can be controlled coherently.

Light could be used to carry quantum information in networks, but this requires methods to prepare and control individual photons. A superconducting circuit can controllably emit photons in either direction along a microwave waveguide.

Ionizing radiation from cosmic rays has been identified as a source of correlated errors in superconducting qubits, but a direct demonstration of this link has been lacking. Here the authors measure the coincidence between correlated errors and incident cosmic rays in a chip with 10 transmon qubits.

Arrays of superconducting transmon qubits can be used to study the Bose–Hubbard model. Synthetic electromagnetic fields have now been added to this analogue quantum simulation platform.

Superconducting giant atoms are realized in a waveguide by coupling small atoms to the waveguide at multiple discrete locations, producing tunable atom–waveguide coupling and enabling decoherence-free interactions.

By emulating a 2D hard-core Bose–Hubbard lattice using a controllable 4 × 4 array of superconducting qubits, volume-law entanglement scaling as well as area-law scaling at different locations in the energy spectrum are observed.

Parametric amplifiers are a key component in the operation and readout of superconducting quantum circuits. An improved travelling-wave amplifier design enables broadband squeezing and high-performance operation.

Accurately characterizing the noise influencing quantum devices is instrumental to improve coherence properties and design more robust control protocols. Sung et al. demonstrate non-Gaussian noise spectroscopy with a superconducting qubit, enabling the detection and characterization of dephasing noise without assuming Gaussian statistics.

Scalable quantum information processing requires controllable high-coherence qubits. Here, the authors present superconducting flux qubits with broad frequency tunability, strong anharmonicity and high reproducibility, identifying photon shot noise as the main source of dephasing for further improvements.

Ionizing radiation from environmental radioactivity and cosmic rays increases the density of broken Cooper pairs in superconducting qubits, reducing their coherence times, but can be partially mitigated by lead shielding.

Engineering qubits with long coherence times requires the ability to distinguish multiple noise sources, which is not possible with typical two-level qubit sensors. Here the authors utilize the multiple level transitions of a superconducting qubit to characterize two common types of external noise.

Quantum annealers hold promise of outperforming classical computers in solving hard optimization problems, but one main challenge is understanding the role of noise in quantum annealing. Here, the authors characterize the relevant noise sources in a tunable flux qubit, a building block for quantum annealers, and provide a benchmark for future work on highly-coherent quantum annealers.

The presence of various noises in the qubit environment is a major limitation on qubit coherence time. Here, the authors demonstrate the use a closed-loop feedback to stabilize frequency noise in a flux-tunable superconducting qubit and suggest this as a scalable approach applicable to other types of noise.

The complexity of many-body quantum states makes their evolution difficult to simulate with classical computers. Experiments on a 2D nine-qubit device demonstrate that the key properties of quantum lattices can be accessed by measuring out-of-time-ordered correlators.

Parallel-plate capacitors of the two-dimensional materials hBN and NbSe₂ are integrated with aluminium Josephson junctions to realize transmon qubits with coherence times reaching 25 μs.