A way to induce quantum stability Dynamical systems, whether classical or quantum, usually require a method stabilize performance and maintain the required state. For instance, communication between computers requires error correction codes ensure that information is transferred correctly. In system, however, very act of measuring it can perturb it. Leghtas et al. show engineering interaction system its environment for delicate states, process could simplify processing. Science , this issue p. 853

The nature of fractional quantum Hall (FQH) states is determined by the interplay between Coulomb interaction and symmetries system. distinct combination spin, valley, orbital degeneracies in bilayer graphene predicted to produce an unusual tunable sequence FQH states. Here, we present local electronic compressibility measurements effect lowest Landau level graphene. We observe incompressible at filling factors ν = 2p + 2/3, with hints additional appearing 3/5, where p -2, -1, 0, 1. This...

We have realized a new interaction between superconducting qubits and readout cavity that results in the displacement of coherent state cavity, conditioned on qubit. This conditional state, when it reaches cavity-following, phase-sensitive amplifier, matches its measured observable, namely, phase quadrature. In setup where several are coupled to same resonator, we show is possible measure target qubit with minimal dephasing other qubits. Our suggest novel directions for faster...

Abstract We present a protected superconducting qubit based on an effective circuit element that only allows pairs of Cooper to tunnel. These dynamics give rise nearly degenerate ground state manifold indexed by the parity tunneled pairs. show that, when is shunted large capacitance, this can be used as logical we expect insensitive multiple relaxation and dephasing mechanisms.

We realize a hybrid superconductor-semiconductor transmon device in which the Josephson effect is controlled by gate-defined quantum dot an InAs/Al nanowire. Microwave spectroscopy of transmon's transition spectrum allows us to probe ground state parity as function gate voltages, external magnetic flux, and field applied parallel The measured phase diagram agreement with that predicted single-impurity Anderson model superconducting leads. Through continuous time monitoring circuit we...

We use a hybrid superconductor-semiconductor transmon device to perform spectroscopy of quantum dot Josephson junction tuned be in spin-1/2 ground state with an unpaired quasiparticle. Because spin-orbit coupling, we resolve two flux-sensitive branches the spectrum, depending on spin A finite magnetic field shifts energy, favoring one and resulting anomalous effect. demonstrate excitation direct spin-flip transition using all-electrical control. Manipulation control enable future...

We describe here the use of high-temperature oxidation and reduction to produce highly crystalline nanoparticles Ni NiO. Starting with an amorphous powder, we demonstrate that at $900\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ produces faceted NiO nanocrystals sizes ranging from 20 60 nm. High-resolution transmission electron microscopy measurements indicate near-perfect atomic order, truncated by (200) surfaces. Magnetization reveal N\'eel temperature these is 480 K, substantially...

We have determined how the anomalous exchange bias effect in Co/CoO nanoparticles of 11 nm diameter depends on Co core and CoO shell dimensions. The oxidation used this study is carefully controlled, yielding highly crystalline oriented interfaces. dimensions are from magnetization small angle x-ray scattering measurements. field core-shell nonmonotonically thickness, reaching a maximum value $\ensuremath{\approx}7\text{ }\text{kOe}$ at 30 K when similar. propose that lattice strain induces...

Isolation from the environment determines extent to which charge is confined on an island, manifests as Coulomb oscillations, such dispersion. We investigate dispersion of a nanowire transmon hosting quantum dot in junction. observe rapid suppression with increasing junction transparency, consistent predicted scaling law, incorporates two branches Josephson potential. find improved qubit coherence times at point highest suppression, suggesting novel approaches for building charge-insensitive qubits.

We present a method for calculating the energy levels of superconducting circuits that contain highly anharmonic, inductively shunted modes with arbitrarily strong coupling. Our starts by normal linearized circuit and proceeds numerical diagonalization in this basis. As an example, we analyze Hamiltonian fluxonium qubit coupled to readout resonator. While elementary, simple example is nontrivial because it cannot be efficiently treated known as ``black-box quantization,'' bare harmonic...

Artificial molecules built from superconducting circuits can potentially be used as probes of external fields that cannot studied with devices naturally occurring atoms. A new study demonstrates how the magnetic moment a molecule two artificial fluxonium atoms changes in response to an field.

Circuit quantum electrodynamics, where photons are coherently coupled to artificial atoms built with superconducting circuits, has enabled the investigation and control of macroscopic quantum-mechanical phenomena in superconductors. Recently, hybrid circuits incorporating semiconducting nanowires other electrostatically-gateable elements have provided new insights into mesoscopic superconductivity. Extending capabilities flux-based work magnetic fields would be especially useful both as a...

We report the detection of a gate-tunable kinetic inductance in hybrid InAs/Al nanowire. For this purpose, we have embedded nanowire into quarter-wave coplanar waveguide resonator and measured resonance frequency circuit. find that can be changed via gate voltage controls electron density proximitized semiconductor thus inductance. Applying Mattis-Bardeen theory, extract dependence normal state conductivity nanowire, as well its superconducting gap. Our measurements complement existing...

Dispersive readout is widely used to perform high-fidelity measurement of superconducting qubits. Much work has been focused on the qubit fidelity, which depends achievable signal-to-noise ratio and relaxation time. As groups have pushed increase fidelity by increasing photon number, dispersive shown strongly affect post-measurement state. Such effects hinder effectiveness quantum error correction, requires measurements that both high are non-demolition (QND). Here, we experimentally...

Aluminum-based Josephson junctions are currently the main sources of nonlinearity for control and manipulation superconducting qubits. A phase-slip junction, dual a provides an alternative source that promises new types protected qubits possibility high-temperature high-frequency operation through use superconductors with larger energy gaps. Phase-slip have been challenging, however, to incorporate into because difficulty controlling junction parameters. Here we demonstrate qubit based on...

We report measurements of resistance oscillations in micron-scale antidots both the integer and fractional quantum Hall regimes. In regime, we conclude that are Coulomb type from scaling magnetic field period with number edges bound to antidot. Based on gate-voltage periods, find at filling factor {\nu} = 2 a tunneling charge e two charged edges. Generalizing this picture (again, based periods) 2/3 (2/3)e single edge.

Quantum computing hardware is much more susceptible to errors than classical hardware. While quantum error correction can combat these errors, the noise affecting must be understood apply proper error-correcting code. Presenting an approach for determining in real time whether qubit are correlated, authors simultaneously monitor two fluxonium qubits and measure correlations between their relaxation times. This analysis method architecture generalized multiqubit systems, where applying right...

Superconducting artificial atoms are an emerging platform for the study of coherent quantum physics, and computation. However, their level-transition properties currently much simpler than those true atoms, which limits systems that can be implemented with this hardware. Here researchers use a nonlinear coupling element to engineer selection rules fluxonium circuit, thus gain access previously forbidden transitions. Such technique allows us expand set operations possible using...

We investigate dynamic nuclear polarization in quantum point contacts (QPCs) the integer and fractional Hall regimes. Following application of a dc bias, plateaus QPC shift symmetrically about half filling lowest Landau level, ν=1/2, suggesting an interpretation terms composite fermions. Polarizing detecting at different factors indicates that Zeeman energy is reduced by induced polarization. Mapping effects from to regimes extends fermion picture include hyperfine coupling.

High-coherence qubits, which can store and manipulate quantum states for long times with low error rates, are necessary building blocks computers. Here we propose a driven superconducting erasure qubit, the Floquet fluxonium molecule, minimizes bit-flip rates through disjoint support of its qubit suppresses phase flips by novel second-order insensitivity to flux-noise dephasing. We estimate bit-flip, phase-flip, numerical simulations, predicted coherence approximately 50 ms in computational...

Converting quantum information from stationary qubits to traveling photons enables both fast qubit initialization and efficient generation of flying for redistribution information. This conversion can be performed using cavity-sideband transitions. In the fluxonium, however, direct transitions are forbidden due parity symmetry. Here we circumvent this selection rule by a three-wave mixing element couple fluxonium resonator. We experimentally demonstrate scheme interfacing with through...