arXiv subjects

J. Senior

Publications and source records attributed to J. Senior.

5 recordsLinked to original sources

arXiv2025

Fast optical data transfer into a Josephson junction array

We employ externally shunted Nb-AlO$_x$-Nb Josephson junctions for demonstrating a circuit that is suitable for an optically driven Josephson Arbitrary Waveform Synthesizer (JAWS). This technology enables overdamped junctions with characteristic frequencies above 100 GHz and critical currents of the order of 100 $\mu$A, which is promising, e.g., for low-dissipation optical control of quantum circuits such as superconducting quantum bits. Here we utilize a double-pulse technique to experimentally determine the maximum rate at which optical pulse data can be reliably delivered to the superconducting circuit. We demonstrate the feasibility of data transfer up to 60 Gbit/s, which is about factor 4 higher than for typical JAWS.

cond-mat.supr-con↗

arXiv2024

Dual relaxation oscillations in a Josephson junction array

We report relaxation oscillations in a one-dimensional array of Josephson junctions. The oscillations are circuit-dual to those ordinarily observed in single junctions. The dual circuit quantitatively accounts for temporal dynamics of the array, including the dependence on biasing conditions. Injection locking the oscillations results in well-developed current plateaux. A thermal model explains the relaxation step of the oscillations.

cond-mat.mes-hall↗

arXiv2022

Superconductivity from a melted insulator

Quantum phase transitions typically result in a broadened critical or crossover region at nonzero temperature. Josephson arrays are a model of this phenomenon, exhibiting a superconductor-insulator transition at a critical wave impedance, and a well-understood insulating phase. Yet high-impedance arrays used in quantum computing and metrology apparently evade this transition, displaying superconducting behavior deep into the nominally insulating regime. The absence of critical behavior in such devices is not well understood. Here we show that, unlike the typical quantum-critical broadening scenario, in Josephson arrays temperature dramatically shifts the critical region. This shift leads to a regime of superconductivity at high temperature, arising from the melted zero-temperature insulator. Our results quantitatively explain the low-temperature onset of superconductivity in nominally insulating regimes, and the transition to the strongly insulating phase. We further present, to our knowledge, the first understanding of the onset of anomalous-metallic resistance saturation. This work demonstrates a non-trivial interplay between thermal effects and quantum criticality. A practical consequence is that, counterintuitively, the coherence of high-impedance quantum circuits is expected to be stabilized by thermal fluctuations.

cond-mat.mes-hall↗

arXiv2021

Detecting induced $p \pm ip$ pairing at the Al-InAs interface with a quantum microwave circuit

Superconductor-semiconductor hybrid devices are at the heart of several proposed approaches to quantum information processing, but their basic properties remain to be understood. We embed a two-dimensional Al-InAs hybrid system in a resonant microwave circuit, probing the breakdown of superconductivity due to an applied magnetic field. We find a strong fingerprint from the two-component nature of the hybrid system, and quantitatively compare with a theory that includes the contribution of intraband $p \pm i p$ pairing in the InAs, as well as the emergence of Bogoliubov-Fermi surfaces due to magnetic field. Separately resolving the Al and InAs contributions allows us to determine the carrier density and mobility in the InAs.

cond-mat.supr-con↗

arXiv2015

Direct measurements of the extraordinary optical momentum and transverse spin-dependent force using a nano-cantilever

Known since Kepler's observation that a comet's tail is oriented away from the sun, radiation pressure stimulated remarkable discoveries in electromagnetism, quantum physics and relativity [1,2]. This phenomenon plays a crucial role in a variety of systems, from atomic [3-5] to astronomical [6] scales. The pressure of light is associated with the momentum of photons, and it is usually assumed that both the optical momentum and the radiation-pressure force are naturally aligned with the propagation of light, i.e., its wavevector. Here we report the direct observation of an extraordinary optical momentum and force directed perpendicular to the wavevector, and proportional to the optical spin (i.e., degree of circular polarization). Such optical force was recently predicted for evanescent waves [7] and other structured fields [8]. It can be associated with the enigmatic "spin-momentum" part of the Poynting vector, which was introduced by Belinfante in field theory 75 years ago [9-11]. We measure this unusual transverse momentum using a nano-cantilever capable of femto-Newton resolution, which is immersed in an evanescent optical field above the total-internal-reflecting glass surface. Furthermore, the transverse force we measure exhibits another polarization-dependent contribution determined by the imaginary part of the complex Poynting vector. By revealing new types of optical forces in structured fields, our experimental findings revisit fundamental momentum properties of light and bring a new twist to optomechanics.

physics.optics↗