I am going to post here all newly submitted articles on the arXiv related to superconducting circuits. If your article has been accidentally forgotten, feel free to contact me
05
Jan
2026
Probing Dark Matter-Electron Interactions with Superconducting Qubits
Quantum device measurements are powerful tools to probe dark matter interactions. Among these, transmon qubits stand out for their ability to suppress external noise while remaining
highly sensitive to tiny energy deposits. Ambient galactic halo dark matter interacting with electrons can deposit energy in the qubit, leading to changes in its decoherence time. Recent measurements of transmons have consistently measured, in various experimental setups, a residual contribution to the decoherence time unexplained by thermal noise or known external sources. We use such measurements to set the most stringent laboratory-based constraints to date on dark matter-electron scattering at the keV scale and competitive constraints on dark photon absorption.
23
Dez
2025
Systematic Construction of Time-Dependent Hamiltonians for Microwave-Driven Josephson Circuits
Time-dependent electromagnetic drives are fundamental for controlling complex quantum systems, including superconducting Josephson circuits. In these devices, accurate time-dependent
Hamiltonian models are imperative for predicting their dynamics and designing high-fidelity quantum operations. Existing numerical methods, such as black-box quantization (BBQ) and energy-participation ratio (EPR), excel at modeling the static Hamiltonians of Josephson circuits. However, these techniques do not fully capture the behavior of driven circuits stimulated by external microwave drives, nor do they include a generalized approach to account for the inevitable noise and dissipation that enter through microwave ports. Here, we introduce novel numerical techniques that leverage classical microwave simulations that can be efficiently executed in finite element solvers, to obtain the time-dependent Hamiltonian of a microwave-driven superconducting circuit with arbitrary geometries. Importantly, our techniques do not rely on a lumped-element description of the superconducting circuit, in contrast to previous approaches to tackling this problem. We demonstrate the versatility of our approach by characterizing the driven properties of realistic circuit devices in complex electromagnetic environments, including coherent dynamics due to charge and flux modulation, as well as drive-induced relaxation and dephasing. Our techniques offer a powerful toolbox for optimizing circuit designs and advancing practical applications in superconducting quantum computing.
22
Dez
2025
DC-powered broadband quantum-limited microwave amplifier
Fast, high-fidelity, single-shot readout of superconducting qubits in quantum processors demands quantum-limited amplifiers to preserve the optimal signal-to-noise ratio. Typically,
quantum-limited amplification is achieved with parametric down-conversion of a strong pump tone, which imposes significant hardware overhead and severely limits scalability. Here, we demonstrate the first DC-powered broadband amplifier operating within 0.2 photons of the quantum limit. Our impedance-engineered Inelastic Cooper-pair Tunneling Amplifier (ICTA)-a voltage-biased SQUID in which Cooper pairs tunnel inelastically by emitting signal-idler photon pairs-operates in reflection, delivering 13 dB of average gain across a 3.5 GHz bandwidth in a single stage. Semiclassical simulations accurately predict the gain and saturation power, enabling further design improvements. By eliminating the pump-tone infrastructure, the broadband ICTA promises to dramatically reduce the hardware complexity of quantum-limited amplification in superconducting quantum processors.
17
Dez
2025
Enabling Technologies for Scalable Superconducting Quantum Computing
Experiments with superconducting quantum processors have successfully demonstrated the basic functions needed for quantum computation and evidence of utility, albeit without a sizable
array of error-corrected qubits. The realization of the full potential of quantum computing centers on achieving large scale fault-tolerant quantum computers. Science, engineering and industry advances are needed to robustly generate, sustain, and efficiently manipulate an exponentially large computational (Hilbert) space as well as supply the number and quality components needed for such a scaled system. In this article, we suggest critical areas of quantum system and ecosystem development, with respect to the handling and transmission of quantum information within and out of a cryogenic environment, that would accelerate the development of quantum computers based on superconducting circuits.
Coherent transfer via parametric control of normal-mode splitting in a superconducting multimode resonator
Microwave storage and retrieval are essential capabilities for superconducting quantum circuits. Here, we demonstrate an on-chip multimode resonator in which strong parametric modulation
induces a large and tunable normal-mode splitting that enables microwave storage. When the spectral bandwidth of a short microwave pulse covers the two dressed-state absorption peaks, part of the pulse is absorbed and undergoes coherent energy exchange between the modes, producing a clear time-domain beating signal. By switching off the modulation before the beating arrives, we realize on-demand storage and retrieval, demonstrating an alternative approach to microwave photonic quantum memory. This parametric-normal-mode-splitting protocol offers a practical route toward a controllable quantum-memory mechanism in superconducting circuits.
16
Dez
2025
Engineering Anisotropic Rabi Model in Circuit QED
The anisotropic Rabi model (ARM), which features tunable Jaynes-Cummings (JC) and anti-Jaynes-Cummings (AJC) interactions, has remained challenging to realize fully. We present a circuit
QED implementation that provides static control over the ARM parameters. By simultaneously coupling a qubit to a resonator’s voltage and current antinodes, we geometrically tune the interaction from pure JC to pure AJC. This control enables novel quantum measurement capabilities, including dispersive shift cancellation and Purcell-suppressed readout. Our work establishes a direct platform for exploring the ARM’s full parameter space and its applications in quantum information processing.
15
Dez
2025
Genuine Tripartite Strong Coupling in a Superconducting-Spin Hybrid Quantum System
We demonstrate genuine tripartite strong coupling in a solid-state hybrid quantum system comprising a superconducting transmon qubit, a fixed-frequency coplanar-waveguide resonator,
and an ensemble of NV− centers in diamond. Frequency-domain spectroscopy reveals a characteristic three-mode avoided crossing, indicating that single excitations are coherently shared across all three subsystems. At higher probe powers, we observe nonlinear features including multiphoton transitions and signatures of transmon-14N nuclear-spin interactions, highlighting the accessibility of higher-excitation manifolds in this architecture. These results establish a new regime of hybrid cavity QED that integrates superconducting and spin degrees of freedom, providing a platform for exploring complex multicomponent dynamics and developing hybrid quantum interfaces.
Slowing and Storing Microwaves in a Single Superconducting Fluxonium Artificial Atom
Three-level Lambda systems provide a versatile platform for quantum optical phenomena such as Electromagnetically Induced Transparency (EIT), slow light, and quantum memory. Such Lambda
systems have been realized in several quantum hardware platforms including atomic systems, superconducting artificial atoms, and meta-structures. Previous experiments involving superconducting artificial atoms incorporated coupling to additional degrees of freedom, such as resonators or other superconducting atoms. In this work, we performed an EIT experiment in microwave frequency range utilizing a single Fluxonium qubit within a microwave waveguide. The Lambda system is consisted of two plasmon transitions in combination with one metastable state originating from the fluxon transition. In this configuration, the controlling and probing transitions are strongly coupled to the transmission line, safeguarding the transition between 0 and 1 states, and ensuring the Fluxonium qubit is close to the sweet spot. Our observations include the manifestation of EIT, a slowdown of light with a delay time of 217 ns, and photon storage. These results highlight the potential as a phase shifter or quantum memory for quantum communication in superconducting circuits.
11
Dez
2025
A Cryogenic Muon Tagging System Based on Kinetic Inductance Detectors for Superconducting Quantum Processors
Ionizing radiation has emerged as a potential limiting factor for superconducting quantum processors, inducing quasiparticle bursts and correlated errors that challenge fault-tolerant
operation. Atmospheric muons are particularly problematic due to their high energy and penetration power, making passive shielding ineffective. Therefore, monitoring the real-time muon flux is crucial to guide the development of alternative error-correction or protection strategies. We present the design, simulation, and first operation of a cryogenic muon-tagging system based on Kinetic Inductance Detectors (KIDs) for integration with superconducting quantum processors. The system consists of two KIDs arranged in a vertical stack and operated at ~20 mK. Monte Carlo simulations based on Geant4 guided the prototype design and provided reference expectations for muon-tagging efficiency and accidental coincidences due to ambient γ-rays. We measured a muon-induced coincidence rate among the top and bottom detectors of (192 ± 9) × 10−3 events/s, in excellent agreement with the Monte Carlo prediction. The prototype achieves a muon-tagging efficiency of about 90% with negligible dead time. These results demonstrate the feasibility of operating a muon-tagging system at millikelvin temperatures and open the path toward its integration with multi-qubit chips to veto or correct muon-induced errors in real time.
10
Dez
2025
Three-body interaction in a magnon-Andreev-superconducting qubit system: collapse-revival phenomena and entanglement redistribution
Three-body interactions are fundamental for realizing novel quantum phenomena beyond pairwise physics, yet their implementation — particularly among distinct quantum systems —
remains challenging. Here, we propose a hybrid quantum architecture comprising a magnonic mode (in a YIG sphere), an Andreev spin qubit (ASQ), and a superconducting qubit (SCQ), to realize a strong three-body interaction at the single-quantum level. Leveraging the spin-dependent supercurrent and circuit-integration flexibility of the ASQ, it is possible to engineer a strong tripartite coupling that jointly excites both qubits upon magnon annihilation (or excites magnons and SCQs upon ASQ deexcitation). Through analytical and numerical studies, we demonstrate that this interaction induces synchronized collapse and revival in qubit populations when the magnon is initially prepared in a coherent state. Notably, during the collapse region — where populations remain static — the entanglement structure undergoes a dramatic and continuous reorganization. We show that the genuine tripartite entanglement is redistributed into bipartite entanglement between the two qubits, and vice versa, with the total entanglement conserved. These phenomena, unattainable via two-body couplings, underscore the potential of three-body interactions for exploring intrinsically new quantum effects and advancing hybrid quantum information platforms.