Currently available superconducting quantum processors with interconnected transmon qubits are noisy and prone to various errors. The errors can be attributed sources such as open system effects spurious inter-qubit couplings (crosstalk). ZZ-coupling between in fixed frequency architectures is always present contributes both coherent incoherent crosstalk Its suppression therefore a key step towards enhancing the fidelity of computation using transmons. Here we propose use dynamical...

Two distinct types of magnetoresistance oscillations are observed in two electronic Fabry-Perot interferometers different sizes the integer quantum Hall regime. Measuring these as a function magnetic field and gate voltages, we describe three signatures that distinguish types. The $2.0\text{ }\ensuremath{\mu}{\text{m}}^{2}$ device understood to arise from Coulomb blockade mechanism those an $18\text{ Aharonov-Bohm mechanism. This work clarifies, provides ways distinguish, demonstrates...

Significance Transport in the so-called “bad metallic” regime of strongly correlated electron systems with no well-defined electronic quasiparticles has been a long-standing challenge theoretical physics. This motivated collection an ample amount data on bad metals. However, so far, emphasis given to charge sector, host crystal lattice treated as phonon background. In this paper, we show that, for cuprates metallic where resistivity exceeds “Mott–Ioffe–Regel” limit, excitations are also not...

We utilize a superconducting qubit processor to experimentally probe non-Markovian dynamics of an entangled pair. prepare state between two qubits and monitor the evolution entanglement over time as one interacts with small quantum environment consisting auxiliary transmon coupled its readout cavity. observe collapse revival signature memory effects in environment. then engineer non-Markovianity by populating cavity thermal photons show transition from Markovian dynamics, ultimately reaching...

We investigate nonlinear transport in electronic Fabry-Pérot interferometers the integer quantum Hall regime. For sufficiently large that Coulomb blockade effects are absent, a checkerboardlike pattern of conductance oscillations as function dc bias and perpendicular magnetic field is observed. Edge-state velocities extracted from checkerboard data compared to model calculations found be consistent with crossover skipping orbits at low fields E-vector x B-vector drift high fields....

We present a superconducting circuit device that provides active, on-demand, tunable dissipation on target mode of the electromagnetic field. Our is based “dissipator” can be made lossy when tuned into resonance with broadband filter mode. When driven parametrically, this dissipator induces loss any coupled to it energy detuning equal drive frequency. demonstrate use reset qubit’s readout cavity after measurement, removing photons characteristic rate greater than <a:math...

We present transport measurements of unshunted dc superconducting quantum interference devices (SQUIDs) consisting 30 nm wide aluminum nanobridges varying length L contacted with two and three dimensional banks. 3D nanobridge SQUIDs $\leq$ 150 (approximately 3-4 times the coherence length) exhibit $\approx 70%$ critical current modulation applied magnetic field, approaching theoretical limit for an ideal short metallic weak link. In contrast, 2D significantly lower modulation. This enhanced...

We present microwave measurements of a high quality factor superconducting resonator incorporating two aluminum nanobridge Josephson junctions in loop shunted by an on-chip capacitor. Trapped quasiparticles (QPs) shift the resonant frequency, allowing us to probe trapped QP number and energy distribution quantify their lifetimes. find that population obeys Gibbs above 75 mK, with non-Poissonian trapping statistics. Our results are quantitative agreement Andreev bound state model transport,...

Non-Markovian noise presents a particularly relevant challenge in understanding and combating decoherence quantum computers, yet is challenging to capture terms of simple models. Here we show that phenomenological dynamical model known as the post-Markovian master equation (PMME) accurately captures predicts non-Markovian superconducting qubit system. The PMME constructed using experimentally measured state dynamics an IBM Quantum Experience cloud-based processor, thus successfully observed...

A crucial limit to measurement efficiencies of superconducting circuits comes from losses involved when coupling an external quantum amplifier. Here, we realize a device circumventing this problem by directly embedding artificial atom, comprised transmon qubit, within flux-pumped Josephson parametric This configuration is able enhance dispersive without exposing the qubit appreciable excess backaction. Near-optimal backaction obtained engineering circuit permit high-power operation that...

Transmon qubits experience open-system effects that manifest as noise at a broad range of frequencies. We present model these using the Redfield master equation with hybrid bath consisting low- and high-frequency components. use two-level fluctuators to simulate <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mn>1</a:mn><a:mo>/</a:mo><a:mi>f</a:mi></a:math>-like behavior, which is dominant source decoherence for superconducting qubits. By measuring...

We propose and analyze a protocol for stabilizing maximally entangled state of two noninteracting qubits using active state-dependent feedback from continuous two-qubit half-parity measurement in coordination with concurrent, noncommuting dynamical decoupling drive. demonstrate that such drive can be simultaneous the feedback, while also playing key part itself. show robust stabilization near-unit fidelity achieved even presence realistic nonidealities, as time delay loop, imperfect...

We present high-resolution thermal diffusivity measurements on several near optimally doped electron- and hole-doped cuprate systems in a temperature range that passes through the Mott-Ioffe-Regel limit, above which quasiparticle picture fails. Our primary observations are inverse is linear can be fitted to $D_Q^{-1}=aT+b$. The slope $a$ interpreted Planckian relaxation time $τ\approx\hbar/k_BT$ diffusion velocity $v_B$, close, but larger than sound velocity. intercept $b$ represent...

Quasiparticle (QP) effects play a significant role in the coherence and fidelity of superconducting quantum circuits. The Andreev bound states high-transparency Josephson junctions can act as low-energy traps for QPs, providing mechanism studying dynamics properties both QPs junction. Using locally injected thermal we study QP loss poisoning epitaxial Al-InAs incorporated interference device (SQUID) galvanically shorting resonator to ground. We observe changes resonance line shape frequency...

We present the driven response at T=30mK of 6 GHz superconducting resonators constructed from capacitively-shunted three dimensional (3D) aluminum nanobridge quantum interference devices (nanoSQUIDs). observe flux modulation resonant frequency in quantitative agreement with numerical calculation and characteristic near-ideal short weak link junctions. Under strong microwave excitation, we stable bifurcation coupled quality factor (Q) ranging ~30-3500. Near this bias point, parametric...

We present polar Kerr effect measurements of the filled skutterudite superconductor PrOs$_4$Sb$_{12}$. Simultaneous AC susceptibility allow us to observe superconducting transition under influence heating from optical beam. A nonzero angle $\theta_K$ develops below transition, saturating at $\sim 300$ nrad low temperatures. This result is repeated across several multiple samples. By extrapolating measured $\theta_K(T)$ zero power, we are able show that onset temperature in one set consistent...

We describe a dispersive nanoSQUID (nanoscale superconducting quantum interference device) magnetometer comprised of two variable thickness aluminum weak-link Josephson junctions shunted in parallel with an on-chip capacitor. This arrangement forms nonlinear oscillator tunable 4–8 GHz resonant frequency quality factor Q = 30 when coupled directly to 50 Ω transmission line. In the presence near-resonant microwave carrier signal, low flux input generates sidebands that are readily detected...

We describe the theory and implementation of a dispersive magnetometer based on an aluminum nanoSQUID. The nanoSQUID consists superconducting loop interrupted by two variable-thickness weak-link nanobridge Josephson junctions. When is placed in parallel with lumped-element capacitor, it acts as inductive element resonant tank circuit. By performing microwave reflectometry circuit, SQUID inductance can be measured, providing sensitive meter flux threading loop. In this review we provide...

We characterize the flux sensitivity of a dispersive 3D aluminum nanobridge SQUID magnetometer as function applied in-plane magnetic field. In zero field, we observe an effective noise 17 n$\Phi_0$/Hz$^{1/2}$ with 25 MHz bandwidth. Flux increased by less than factor three parallel fields up to 61 mT. Operation in higher may be possible decreasing dimensions shunt capacitor circuit. These devices are thus well suited for observing high-speed dynamics nanoscale magnets, even presence moderate...

We present measurements of 1/f frequency noise in both linear and Josephson-junction-embedded superconducting aluminum resonators the low power, temperature regime - typical operating conditions for qubits. The addition Josephson junction does not result additional noise, thereby placing an upper limit fractional critical current fluctuations $10^{-8}$ (Hz$^{-1/2}$) at 1 Hz sub-micron, shadow evaporated junctions. These values imply a minimum dephasing time qubit due to 40 -- 1400 $\mu$s...

We utilize a superconducting qubit processor to experimentally probe the transition from non-Markovian Markovian dynamics of an entangled pair. prepare state between two qubits and monitor evolution entanglement over time as one interacts with small quantum environment consisting auxiliary transmon coupled its readout cavity. observe collapse revival signature memory effects in environment. then engineer non-Markovianity by populating cavity thermal photons show dynamics, reaching regime...

We present an open-source database of superconducting quantum device designs that may be used as the starting point for customized devices. Each design can generated programmatically using Qiskit Metal package, and simulated finite-element electromagnetic solvers. a robust workflow achieving high accuracy on simulations. Many in are experimentally validated, showing excellent agreement between measured parameters. Our includes front-end interface allows users to generate...