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Biased noise qubits, which can selectively suppress certain types of noise, are advantageous for quantum error correction of bosonic codes. Here the authors make an important step in this direction by demonstrating quantum control of a harmonic oscillator with a biased noise qubit.

The ability to transfer quantum information from a memory to a flying qubit is important for building quantum networks. The very fast release of a multiphoton state in a microwave cavity memory into propagating modes is demonstrated.

Quantum error correction of a logical qutrit and ququart were experimentally realized beyond the break-even point with the Gottesman–Kitaev–Preskill bosonic code.

A noise-resilient protocol implemented in a cavity resonator coupled to a qubit demonstrates that large nonlinear couplings are not a necessary requirement for the fast universal control and state preparation of engineered quantum systems.

Quantum error correction of Gottesman–Kitaev–Preskill code states is realized experimentally in a superconducting quantum device.

The minimum noise energy that a phase-preserving amplifier adds to the signal is fundamentally limited to half a photon. A proposed parametric amplifier based on Josephson junctions should be able to reach this limit at microwave frequencies.

Experimental measurements of high-order out-of-time-order correlators on a superconducting quantum processor show that these correlators remain highly sensitive to the quantum many-body dynamics in quantum computers at long timescales.

A qubit generated and stabilized in a superconducting microwave resonator by encoding it into Schrödinger cat states produced by Kerr nonlinearity and single-mode squeezing shows intrinsic robustness to phase-flip errors.

A study demonstrates the extension of a lifetime of a quantum memory using active quantum error correction and reinforcement learning.

Information leaked by a quantum system into its environment causes decoherence but if it is recorded then it can be used to infer the quantum state. Ficheux et al. monitor the relaxation and dephasing of a qubit and show that this allows all three components of the qubit to be probed simultaneously.

In 1985, experiments revealed the quantum behaviour of a macroscopic degree of freedom: the phase difference across a Josephson junction. The authors recount the history of this milestone for the development of superconducting quantum circuits.

A logical qubit is a two-dimensional subspace of a higher dimensional system, whose manipulation requires precise control over the whole system. Here the authors demonstrate a control strategy which exploits precise knowledge of the Hamiltonian to manipulate a coupled oscillator-transmon system.

A quantum-error-correction system is demonstrated in which natural errors due to energy loss are suppressed by encoding a logical state as a superposition of Schrödinger-cat states, which results in the system reaching the ‘break-even’ point, at which the lifetime of a qubit exceeds the lifetime of the constituents of the system.

The use of microwaves to read and write information in superconducting qubits usually requires magnetic components that are difficult to integrate with chip-based circuits. A cascade of parametric amplifiers is now proposed instead, which could provide a more versatile and noise-free alternative.

Two below-threshold surface code memories on superconducting processors markedly reduce logical error rates, achieving high efficiency and real-time decoding, indicating potential for practical large-scale fault-tolerant quantum algorithms.

Recent progress in solid-state quantum information processing has stimulated the search for amplifiers and frequency converters with quantum-limited performance in the microwave range. Here, a phase-preserving, superconducting parametric amplifier with ultra-low-noise properties has been experimentally realized.

An entangled Bell state of two superconducting quantum bits can be stabilized for an arbitrary time using an autonomous feedback scheme, that is, one that does not require a complicated external error-correcting feedback loop.

A quasiparticle in Andreev levels was coupled to a superconducting microwave resonator and its spin was monitored in real time. This has potential applications in the readout of superconducting spin qubits and measurements of Majorana fermions.

Experiment overturns Bohr’s view of quantum jumps, demonstrating that they possess a degree of predictability and when completed are continuous, coherent and even deterministic.

Two superconducting cavity modes are entangled using an exponential-SWAP logic gate.

The long-predicted suppression of quasiparticle dissipation in a Josephson junction when the phase difference across the junction is π is inferred from a sharp maximum in the energy relaxation time of a superconducting artificial atom.

Transistors have continuously reduced in size and increased in switching speed since their invention in 1947. The exponential pace of transistor evolution has led to a revolution in information acquisition, processing and communication technologies. And reigning over most digital applications is a single device structure — the field-effect transistor (FET). But as device dimensions approach the nanometre scale, quantum effects become increasingly important for device operation, and conceptually new transistor structures may need to be adopted. A notable example of such a structure is the single-electron transistor, or SET^1,2,3,4. Although it is unlikely that SETs will replace FETs in conventional electronics, they should prove useful in ultra-low-noise analog applications. Moreover, because it is not affected by the same technological limitations as the FET, the SET can approach closely the quantum limit of sensitivity. It might also be a useful read-out device for a solid-state quantum computer.