@article{13264, abstract = {We build a parametric amplifier with a Josephson field-effect transistor (JoFET) as the active element. The resonant frequency of the device is field-effect tunable over a range of 2 GHz. The JoFET amplifier has 20 dB of gain, 4 MHz of instantaneous bandwidth, and a 1-dB compression point of -125.5 dBm when operated at a fixed resonance frequency. }, author = {Phan, Duc T and Falthansl-Scheinecker, Paul and Mishra, Umang and Strickland, W. M. and Langone, D. and Shabani, J. and Higginbotham, Andrew P}, issn = {2331-7019}, journal = {Physical Review Applied}, number = {6}, publisher = {American Physical Society}, title = {{Gate-tunable superconductor-semiconductor parametric amplifier}}, doi = {10.1103/PhysRevApplied.19.064032}, volume = {19}, year = {2023}, } @article{14032, abstract = {Arrays of Josephson junctions are governed by a competition between superconductivity and repulsive Coulomb interactions, and are expected to exhibit diverging low-temperature resistance when interactions exceed a critical level. Here we report a study of the transport and microwave response of Josephson arrays with interactions exceeding this level. Contrary to expectations, we observe that the array resistance drops dramatically as the temperature is decreased—reminiscent of superconducting behaviour—and then saturates at low temperature. Applying a magnetic field, we eventually observe a transition to a highly resistive regime. These observations can be understood within a theoretical picture that accounts for the effect of thermal fluctuations on the insulating phase. On the basis of the agreement between experiment and theory, we suggest that apparent superconductivity in our Josephson arrays arises from melting the zero-temperature insulator.}, author = {Mukhopadhyay, Soham and Senior, Jorden L and Saez Mollejo, Jaime and Puglia, Denise and Zemlicka, Martin and Fink, Johannes M and Higginbotham, Andrew P}, issn = {1745-2481}, journal = {Nature Physics}, keywords = {General Physics and Astronomy}, pages = {1630--1635}, publisher = {Springer Nature}, title = {{Superconductivity from a melted insulator in Josephson junction arrays}}, doi = {10.1038/s41567-023-02161-w}, volume = {19}, year = {2023}, } @article{12913, abstract = {The coexistence of gate-tunable superconducting, magnetic and topological orders in magic-angle twisted bilayer graphene provides opportunities for the creation of hybrid Josephson junctions. Here we report the fabrication of gate-defined symmetry-broken Josephson junctions in magic-angle twisted bilayer graphene, where the weak link is gate-tuned close to the correlated insulator state with a moiré filling factor of υ = −2. We observe a phase-shifted and asymmetric Fraunhofer pattern with a pronounced magnetic hysteresis. Our theoretical calculations of the junction weak link—with valley polarization and orbital magnetization—explain most of these unconventional features. The effects persist up to the critical temperature of 3.5 K, with magnetic hysteresis observed below 800 mK. We show how the combination of magnetization and its current-induced magnetization switching allows us to realise a programmable zero-field superconducting diode. Our results represent a major advance towards the creation of future superconducting quantum electronic devices.}, author = {Díez-Mérida, J. and Díez-Carlón, A. and Yang, S. Y. and Xie, Y. M. and Gao, X. J. and Senior, Jorden L and Watanabe, K. and Taniguchi, T. and Lu, X. and Higginbotham, Andrew P and Law, K. T. and Efetov, Dmitri K.}, issn = {2041-1723}, journal = {Nature Communications}, publisher = {Springer Nature}, title = {{Symmetry-broken Josephson junctions and superconducting diodes in magic-angle twisted bilayer graphene}}, doi = {10.1038/s41467-023-38005-7}, volume = {14}, year = {2023}, } @article{10851, abstract = {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 twodimensional Al-InAs hybrid system in a resonant microwave circuit, probing the breakdown of superconductivity due to an applied magnetic field. We find a fingerprint from the two-component nature of the hybrid system, and quantitatively compare with a theory that includes the contribution of intraband p±ip 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.}, author = {Phan, Duc T and Senior, Jorden L and Ghazaryan, Areg and Hatefipour, M. and Strickland, W. M. and Shabani, J. and Serbyn, Maksym and Higginbotham, Andrew P}, issn = {1079-7114}, journal = {Physical Review Letters}, keywords = {General Physics and Astronomy}, number = {10}, publisher = {American Physical Society}, title = {{Detecting induced p±ip pairing at the Al-InAs interface with a quantum microwave circuit}}, doi = {10.1103/physrevlett.128.107701}, volume = {128}, year = {2022}, } @article{10589, abstract = {Superconducting devices ubiquitously have an excess of broken Cooper pairs, which can hamper their performance. It is widely believed that external radiation is responsible but a study now suggests there must be an additional, unknown source.}, author = {Higginbotham, Andrew P}, issn = {1745-2481}, journal = {Nature Physics}, keywords = {superconducting devices, superconducting properties and materials}, pages = {126}, publisher = {Springer Nature}, title = {{A secret source}}, doi = {10.1038/s41567-021-01459-x}, volume = {18}, year = {2022}, } @misc{13080, abstract = {Data for the manuscript 'Closing of the Induced Gap in a Hybrid Superconductor-Semiconductor Nanowire' ([2006.01275] Closing of the Induced Gap in a Hybrid Superconductor-Semiconductor Nanowire (arxiv.org)) We upload a pdf with extended data sets, and the raw data for these extended datasets as well.}, author = {Puglia, Denise and Martinez, Esteban and Menard, Gerbold and Pöschl, Andreas and Gronin, Sergei and Gardner, Geoffrey and Kallaher, Ray and Manfra, Michael and Marcus, Charles and Higginbotham, Andrew P and Casparis, Lucas}, publisher = {Zenodo}, title = {{Data for 'Closing of the Induced Gap in a Hybrid Superconductor-Semiconductor Nanowire}}, doi = {10.5281/ZENODO.4592435}, year = {2021}, } @article{9570, abstract = {We present conductance-matrix measurements in long, three-terminal hybrid superconductor-semiconductor nanowires, and compare with theoretical predictions of a magnetic-field-driven, topological quantum phase transition. By examining the nonlocal conductance, we identify the closure of the excitation gap in the bulk of the semiconductor before the emergence of zero-bias peaks, ruling out spurious gap-closure signatures from localized states. We observe that after the gap closes, nonlocal signals and zero-bias peaks fluctuate strongly at both ends, inconsistent with a simple picture of clean topological superconductivity.}, author = {Puglia, Denise and Martinez, E. A. and Ménard, G. C. and Pöschl, A. and Gronin, S. and Gardner, G. C. and Kallaher, R. and Manfra, M. J. and Marcus, C. M. and Higginbotham, Andrew P and Casparis, L.}, issn = {24699969}, journal = {Physical Review B}, number = {23}, publisher = {American Physical Society}, title = {{Closing of the induced gap in a hybrid superconductor-semiconductor nanowire}}, doi = {10.1103/PhysRevB.103.235201}, volume = {103}, year = {2021}, } @misc{9636, author = {Higginbotham, Andrew P}, publisher = {Institute of Science and Technology Austria}, title = {{Data for "Breakdown of induced p ± ip pairing in a superconductor-semiconductor hybrid"}}, year = {2021}, } @unpublished{10029, abstract = {Superconductor-semiconductor hybrids are platforms for realizing effective p-wave superconductivity. Spin-orbit coupling, combined with the proximity effect, causes the two-dimensional semiconductor to inherit p±ip intraband pairing, and application of magnetic field can then result in transitions to the normal state, partial Bogoliubov Fermi surfaces, or topological phases with Majorana modes. Experimentally probing the hybrid superconductor-semiconductor interface is challenging due to the shunting effect of the conventional superconductor. Consequently, the nature of induced pairing remains an open question. Here, we use the circuit quantum electrodynamics architecture to probe induced superconductivity in a two dimensional Al-InAs hybrid system. We observe a strong suppression of superfluid density and enhanced dissipation driven by magnetic field, which cannot be accounted for by the depairing theory of an s-wave superconductor. These observations are explained by a picture of independent intraband p±ip superconductors giving way to partial Bogoliubov Fermi surfaces, and allow for the first characterization of key properties of the hybrid superconducting system.}, author = {Phan, Duc T and Senior, Jorden L and Ghazaryan, Areg and Hatefipour, M. and Strickland, W. M. and Shabani, J. and Serbyn, Maksym and Higginbotham, Andrew P}, booktitle = {arXiv}, title = {{Breakdown of induced p±ip pairing in a superconductor-semiconductor hybrid}}, year = {2021}, } @article{7477, abstract = {We present conductance-matrix measurements of a three-terminal superconductor-semiconductor hybrid device consisting of two normal leads and one superconducting lead. Using a symmetry decomposition of the conductance, we find that antisymmetric components of pairs of local and nonlocal conductances qualitatively match at energies below the superconducting gap, and we compare this finding with symmetry relations based on a noninteracting scattering matrix approach. Further, the local charge character of Andreev bound states is extracted from the symmetry-decomposed conductance data and is found to be similar at both ends of the device and tunable with gate voltage. Finally, we measure the conductance matrix as a function of magnetic field and identify correlated splittings in low-energy features, demonstrating how conductance-matrix measurements can complement traditional single-probe measurements in the search for Majorana zero modes.}, author = {Ménard, G. C. and Anselmetti, G. L. R. and Martinez, E. A. and Puglia, D. and Malinowski, F. K. and Lee, J. S. and Choi, S. and Pendharkar, M. and Palmstrøm, C. J. and Flensberg, K. and Marcus, C. M. and Casparis, L. and Higginbotham, Andrew P}, issn = {0031-9007}, journal = {Physical Review Letters}, number = {3}, publisher = {APS}, title = {{Conductance-matrix symmetries of a three-terminal hybrid device}}, doi = {10.1103/physrevlett.124.036802}, volume = {124}, year = {2020}, } @article{7478, abstract = {Two-terminal conductance spectroscopy of superconducting devices is a common tool for probing Andreev and Majorana bound states. Here, we study theoretically a three-terminal setup, with two normal leads coupled to a grounded superconducting terminal. Using a single-electron scattering matrix, we derive the subgap conductance matrix for the normal leads and discuss its symmetries. In particular, we show that the local and the nonlocal elements of the conductance matrix have pairwise identical antisymmetric components. Moreover, we find that the nonlocal elements are directly related to the local BCS charges of the bound states close to the normal probes and we show how the BCS charge of overlapping Majorana bound states can be extracted from experiments.}, author = {Danon, Jeroen and Hellenes, Anna Birk and Hansen, Esben Bork and Casparis, Lucas and Higginbotham, Andrew P and Flensberg, Karsten}, issn = {0031-9007}, journal = {Physical Review Letters}, number = {3}, publisher = {APS}, title = {{Nonlocal conductance spectroscopy of Andreev bound states: Symmetry relations and BCS charges}}, doi = {10.1103/physrevlett.124.036801}, volume = {124}, year = {2020}, } @article{7145, abstract = {End-to-end correlated bound states are investigated in superconductor-semiconductor hybrid nanowires at zero magnetic field. Peaks in subgap conductance are independently identified from each wire end, and a cross-correlation function is computed that counts end-to-end coincidences, averaging over thousands of subgap features. Strong correlations in a short, 300-nm device are reduced by a factor of 4 in a long, 900-nm device. In addition, subgap conductance distributions are investigated, and correlations between the left and right distributions are identified based on their mutual information.}, author = {Anselmetti, G. L. R. and Martinez, E. A. and Ménard, G. C. and Puglia, D. and Malinowski, F. K. and Lee, J. S. and Choi, S. and Pendharkar, M. and Palmstrøm, C. J. and Marcus, C. M. and Casparis, L. and Higginbotham, Andrew P}, issn = {2469-9969}, journal = {Physical Review B}, number = {20}, publisher = {American Physical Society}, title = {{End-to-end correlated subgap states in hybrid nanowires}}, doi = {10.1103/physrevb.100.205412}, volume = {100}, year = {2019}, } @article{6368, abstract = {An optical network of superconducting quantum bits (qubits) is an appealing platform for quantum communication and distributed quantum computing, but developing a quantum-compatible link between the microwave and optical domains remains an outstanding challenge. Operating at T < 100 mK temperatures, as required for quantum electrical circuits, we demonstrate a mechanically mediated microwave–optical converter with 47% conversion efficiency, and use a classical feed-forward protocol to reduce added noise to 38 photons. The feed-forward protocol harnesses our discovery that noise emitted from the two converter output ports is strongly correlated because both outputs record thermal motion of the same mechanical mode. We also discuss a quantum feed-forward protocol that, given high system efficiencies, would allow quantum information to be transferred even when thermal phonons enter the mechanical element faster than the electro-optic conversion rate.}, author = {Higginbotham, Andrew P and Burns, P. S. and Urmey, M. D. and Peterson, R. W. and Kampel, N. S. and Brubaker, B. M. and Smith, G. and Lehnert, K. W. and Regal, C. A.}, issn = {1745-2473}, journal = {Nature Physics}, number = {10}, pages = {1038--1042}, publisher = {Springer Nature}, title = {{Harnessing electro-optic correlations in an efficient mechanical converter}}, doi = {10.1038/s41567-018-0210-0}, volume = {14}, year = {2018}, } @article{6369, abstract = {We construct a metamaterial from radio-frequency harmonic oscillators, and find two topologically distinct phases resulting from dissipation engineered into the system. These phases are distinguished by a quantized value of bulk energy transport. The impulse response of our circuit is measured and used to reconstruct the band structure and winding number of circuit eigenfunctions around a dark mode. Our results demonstrate that dissipative topological transport can occur in a wider class of physical systems than considered before.}, author = {Rosenthal, Eric I. and Ehrlich, Nicole K. and Rudner, Mark S. and Higginbotham, Andrew P and Lehnert, K. W.}, issn = {2469-9950}, journal = {Physical Review B}, number = {22}, publisher = {American Physical Society (APS)}, title = {{Topological phase transition measured in a dissipative metamaterial}}, doi = {10.1103/physrevb.97.220301}, volume = {97}, year = {2018}, } @article{93, abstract = {An electro-optomechanical device capable of microwave-to-optics conversion has recently been demonstrated, with the vision of enabling optical networks of superconducting qubits. Here we present an improved converter design that uses a three-dimensional microwave cavity for coupling between the microwave transmission line and an integrated LC resonator on the converter chip. The new design simplifies the optical assembly and decouples it from the microwave part of the setup. Experimental demonstrations show that the modular device assembly allows us to flexibly tune the microwave coupling to the converter chip while maintaining small loss. We also find that electromechanical experiments are not impacted by the additional microwave cavity. Our design is compatible with a high-finesse optical cavity and will improve optical performance.}, author = {Menke, Tim and Burns, Peter and Higginbotham, Andrew P and Kampel, N S and Peterson, Robert and Cicak, Katarina and Simmonds, Raymond and Regal, Cindy and Lehnert, Konrad}, journal = {Review of Scientific Instruments}, number = {9}, publisher = {American Institute of Physics}, title = {{Reconfigurable re-entrant cavity for wireless coupling to an electro-optomechanical device}}, doi = {10.1063/1.5000973}, volume = {88}, year = {2017}, } @article{94, abstract = {We introduce a method for breaking Lorentz reciprocity based upon the noncommutation of frequency conversion and delay. The method requires no magnetic materials or resonant physics, allowing for the design of scalable and broadband nonreciprocal circuits. With this approach, two types of gyrators - universal building blocks for linear, nonreciprocal circuits - are constructed. Using one of these gyrators, we create a circulator with >15 dB of isolation across the 5-9 GHz band. Our designs may be readily extended to any platform with suitable frequency conversion elements, including semiconducting devices for telecommunication or an on-chip superconducting implementation for quantum information processing.}, author = {Rosenthal, Eric and Chapman, Benjamin and Higginbotham, Andrew P and Kerckhoff, Joseph and Lehnert, Konrad}, journal = {APS Physics, Physical Review Letters}, number = {14}, publisher = {American Physical Society}, title = {{Breaking Lorentz reciprocity with frequency conversion and delay}}, doi = {10.1103/PhysRevLett.119.147703}, volume = {119}, year = {2017}, } @article{103, abstract = {We investigate effects of quasiparticle poisoning in a Majorana island with strong tunnel coupling to normal-metal leads. In addition to the main Coulomb blockade diamonds, "shadow" diamonds appear, shifted by 1e in gate voltage, consistent with transport through an excited (poisoned) state of the island. Comparison to a simple model yields an estimate of parity lifetime for the strongly coupled island (∼1 μs) and sets a bound for a weakly coupled island (>10 μs). Fluctuations in the gate-voltage spacing of Coulomb peaks at high field, reflecting Majorana hybridization, are enhanced by the reduced lever arm at strong coupling. When converted from gate voltage to energy units, fluctuations are consistent with previous measurements.}, author = {Albrecht, S M and Hansen, Esben and Higginbotham, Andrew P and Kuemmeth, Ferdinand and Jespersen, Thomas and Nygård, Jesper and Krogstrup, Peter and Danon, Jeroen and Flensberg, Karsten and Marcus, Charles}, journal = {APS Physics, Physical Review Letters}, number = {13}, publisher = {American Physical Society}, title = {{Transport signatures of quasiparticle poisoning in a majorana island}}, doi = {10.1103/PhysRevLett.118.137701}, volume = {118}, year = {2017}, } @article{92, abstract = {Advanced organic nonlinear optical (NLO) materials have attracted increasing attention due to their multitude of applications in modern telecommunication devices. Arguably the most important advantage of organic NLO materials, relative to traditionally used inorganic NLO materials, is their short optical response time. Geminal amido esters with their donor-π-acceptor (D-π-A) architecture exhibit high levels of electron delocalization and substantial intramolecular charge transfer, which should endow these materials with short optical response times and large molecular (hyper)polarizabilities. In order to test this hypothesis, the linear and second-order nonlinear optical properties of five geminal amido esters, (E)-ethyl 3-(X-phenylamino)-2-(Y-phenylcarbamoyl)acrylate (1, X = 4-H, Y = 4-H; 2, X = 4-CH3, Y = 4-CH3; 3, X = 4-NO2, Y = 2,5-OCH3; 4, X = 2-Cl, Y = 2-Cl; 5, X = 4-Cl, Y = 4-Cl) were synthesized and characterized, whereby NLO structure-function relationships were established including intramolecular charge transfer characteristics, crystal field effects, and molecular first hyperpolarizabilities (β). Given the typically large errors (10-30%) associated with the determination of β coefficients, three independent methods were used: (i) density functional theory, (ii) hyper-Rayleigh scattering, and (iii) high-resolution X-ray diffraction data analysis based on multipolar modeling of electron densities at each atom. These three methods delivered consistent values of β, and based on these results, 3 should hold the most promise for NLO applications. The correlation between the molecular structure of these geminal amido esters and their linear and nonlinear optical properties thus provide molecular design guidelines for organic NLO materials; this leads to the ultimate goal of generating bespoke organic molecules to suit a given NLO device application.}, author = {Cole, Jaqueline and Lin, Tzechia and Ashcroft, Christopher and Pérez Moreno, Javier and Tan, Yizhou and Venkatesan, Perumal and Higginbotham, Andrew P and Pattison, Philip and Edwards, Alison and Piltz, Ross and Clays, Koen and Ilangovan, Andivelu}, journal = {Journal of Physical Chemistry C}, number = {51}, pages = {29439 -- 29448}, publisher = {American Chemical Society}, title = {{Relating the structure of geminal Amido Esters to their molecular hyperpolarizability}}, doi = {10.1021/acs.jpcc.6b10724}, volume = {120}, year = {2016}, } @article{100, abstract = {We introduce a scheme for preparation, manipulation, and read out of Majorana zero modes in semiconducting wires with mesoscopic superconducting islands. Our approach synthesizes recent advances in materials growth with tools commonly used in quantum-dot experiments, including gate control of tunnel barriers and Coulomb effects, charge sensing, and charge pumping. We outline a sequence of milestones interpolating between zero-mode detection and quantum computing that includes (1) detection of fusion rules for non-Abelian anyons using either proximal charge sensors or pumped current, (2) validation of a prototype topological qubit, and (3) demonstration of non-Abelian statistics by braiding in a branched geometry. The first two milestones require only a single wire with two islands, and additionally enable sensitive measurements of the system\'s excitation gap, quasiparticle poisoning rates, residual Majorana zero-mode splittings, and topological-qubit coherence times. These pre-braiding experiments can be adapted to other manipulation and read out schemes as well.}, author = {Aasen, David and Hell, Michael and Mishmash, Ryan and Higginbotham, Andrew P and Danon, Jeroen and Leijnse, Martin and Jespersen, Thomas and Folk, Joshua and Marcs, Charles and Flensberg, Karsten and Alicea, Jason}, journal = {Physical Review X}, number = {3}, publisher = {American Physical Society}, title = {{Milestones toward Majorana-based quantum computing}}, doi = {10.1103/PhysRevX.6.031016}, volume = {6}, year = {2016}, } @article{101, abstract = {Majorana zero modes are quasiparticle excitations in condensed matter systems that have been proposed as building blocks of fault-tolerant quantum computers. They are expected to exhibit non-Abelian particle statistics, in contrast to the usual statistics of fermions and bosons, enabling quantum operations to be performed by braiding isolated modes around one another. Quantum braiding operations are topologically protected insofar as these modes are pinned near zero energy, with the departure from zero expected to be exponentially small as the modes become spatially separated. Following theoretical proposals, several experiments have identified signatures of Majorana modes in nanowires with proximity-induced superconductivity and atomic chains, with small amounts of mode splitting potentially explained by hybridization of Majorana modes. Here, we use Coulomb-blockade spectroscopy in an InAs nanowire segment with epitaxial aluminium, which forms a proximity-induced superconducting Coulomb island (a â ∼ Majorana islandâ (tm)) that is isolated from normal-metal leads by tunnel barriers, to measure the splitting of near-zero-energy Majorana modes. We observe exponential suppression of energy splitting with increasing wire length. For short devices of a few hundred nanometres, sub-gap state energies oscillate as the magnetic field is varied, as is expected for hybridized Majorana modes. Splitting decreases by a factor of about ten for each half a micrometre of increased wire length. For devices longer than about one micrometre, transport in strong magnetic fields occurs through a zero-energy state that is energetically isolated from a continuum, yielding uniformly spaced Coulomb-blockade conductance peaks, consistent with teleportation via Majorana modes. Our results help to explain the trivial-to-topological transition in finite systems and to quantify the scaling of topological protection with end-mode separation.}, author = {Albrecht, S M and Higginbotham, Andrew P and Jespersen, Thomas and Madsen, Morten and Kuemmeth, Ferdinand and Nygård, Jesper and Krogstrup, Peter and Marcus, Charles}, journal = {Nature}, number = {7593}, pages = {206 -- 209}, publisher = {Nature Publishing Group}, title = {{Exponential protection of zero modes in Majorana islands}}, doi = {10.1038/nature17162}, volume = {531}, year = {2016}, }