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Muthusubramanian, N. (author), Finkel, M. (author), Duivestein, W.J. (author), Zachariadis, C. (author), van der Meer, S.L.M. (author), Veen, H.M. (author), Beekman, M.C. (author), Stavenga, T. (author), Bruno, A. (author), DiCarlo, L. (author)We investigate die-level and wafer-scale uniformity of Dolan-bridge and bridgeless Manhattan-style Josephson junctions, using multiple substrates with and without through-silicon vias (TSVs). Dolan junctions fabricated on planar substrates have the highest yield and lowest room-temperature conductance spread, equivalent to ∼ 100 M H z in...journal article 2024
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Varbanov, B.M. (author), Finkel, M. (author), Veen, H.M. (author), van der Meer, S.L.M. (author), Valles Sanclemente, S. (author), Muthusubramanian, N. (author), Beekman, M.C. (author), Haider, S.N. (author), Terhal, B.M. (author), DiCarlo, L. (author)Minimizing leakage from computational states is a challenge when using many-level systems like superconducting quantum circuits as qubits. We realize and extend the quantum-hardware-efficient, all-microwave leakage reduction unit (LRU) for transmons in a circuit QED architecture proposed by Battistel et al. This LRU effectively reduces...journal article 2023
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Valles Sanclemente, S. (author), van der Meer, S.L.M. (author), Finkel, M. (author), Muthusubramanian, N. (author), Beekman, M.C. (author), Ali, H.A.S. (author), Ferreira Marques, J.M. (author), Zachariadis, C. (author), Veen, H.M. (author), Stavenga, T. (author), Haider, S.N. (author), DiCarlo, L. (author)We present the use of a set of airbridges to trim the frequency of microwave coplanar-waveguide (CPW) resonators post-fabrication. This method is compatible with the fabrication steps of conventional CPW airbridges and crossovers and increases device yield by allowing compensation of design and fabrication uncertainty with 100 MHz range and...journal article 2023
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Vlothuizen, W.J. (author), Ferreira Marques, J.M. (author), van Straten, J. (author), Ali, H. (author), Muthusubramanian, N. (author), Zachariadis, C. (author), van Someren, J. (author), Beekman, M. (author), Haider, S.N. (author), Bruno, A. (author), Almudever, Carmen G. (author), DiCarlo, L. (author)Artificial neural networks are becoming an integral part of digital solutions to complex problems. However, employing neural networks on quantum processors faces challenges related to the implementation of non-linear functions using quantum circuits. In this paper, we use repeat-until-success circuits enabled by real-time control-flow...journal article 2023
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Sagastizabal, R.E. (author), Klaver, B. A. (author), Rol, M.A. (author), Negîrneac, V. (author), Zou, X. (author), Muthusubramanian, N. (author), Beekman, M. (author), Zachariadis, C. (author), Ostroukh, V.P. (author), Haider, S.N. (author), Bruno, A. (author), DiCarlo, L. (author)The preparation of thermal equilibrium states is important for the simulation of condensed matter and cosmology systems using a quantum computer. We present a method to prepare such mixed states with unitary operators and demonstrate this technique experimentally using a gate-based quantum processor. Our method targets the generation of...journal article 2021
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Negîrneac, V. (author), Ali, H.A.S. (author), Muthusubramanian, N. (author), Battistel, F. (author), Sagastizabal, R.E. (author), Moreira, M. S. (author), Ferreira Marques, J.M. (author), Vlothuizen, W.J. (author), Beekman, M.C. (author), Zachariadis, C. (author), Haider, S.N. (author), Bruno, A. (author), DiCarlo, L. (author)Simple tuneup of fast two-qubit gates is essential for the scaling of quantum processors. We introduce the sudden variant (SNZ) of the net zero scheme realizing controlled-Z (CZ) gates by flux control of transmon frequency. SNZ CZ gates realized in a multitransmon processor operate at the speed limit of transverse coupling between...journal article 2021
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Bultink, C.C. (author), O'Brien, T. E. (author), Vollmer, R. (author), Muthusubramanian, N. (author), Beekman, M. W. (author), Rol, M.A. (author), Fu, X. (author), Tarasinski, B.M. (author), Ostroukh, V.P. (author), Varbanov, B.M. (author), Bruno, A. (author), DiCarlo, L. (author)Protecting quantum information from errors is essential for large-scale quantum computation. Quantum error correction (QEC) encodes information in entangled states of many qubits and performs parity measurements to identify errors without destroying the encoded information. However, traditional QEC cannot handle leakage from the qubit...journal article 2020
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Sagastizabal, R.E. (author), Bonet Monroig, X. (author), Singh, Malay (author), Rol, M.A. (author), Bultink, C.C. (author), Fu, X. (author), Ostroukh, V.P. (author), Muthusubramanian, N. (author), Bruno, A. (author), Beekman, M.C. (author), Haider, S.N. (author), O'Brien, T.E. (author), DiCarlo, L. (author)Variational quantum eigensolvers offer a small-scale testbed to demonstrate the performance of error mitigation techniques with low experimental overhead. We present successful error mitigation by applying the recently proposed symmetry verification technique to the experimental estimation of the ground-state energy and ground state of the...journal article 2019
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Rol, M.A. (author), Battistel, F. (author), Malinowski, F.K. (author), Bultink, C.C. (author), Tarasinski, B.M. (author), Vollmer, R. (author), Haider, S.N. (author), Muthusubramanian, N. (author), Bruno, A. (author), Terhal, B.M. (author), DiCarlo, L. (author)Conditional-phase (cz) gates in transmons can be realized by flux pulsing computational states towards resonance with noncomputational ones. We present a 40 ns cz gate based on a bipolar flux pulse suppressing leakage (0.1%) by interference and approaching the speed limit set by exchange coupling. This pulse harnesses a built-in echo to...journal article 2019
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Muthusubramanian, N. (author), Galan, E. (author), Maity, C. (author), Eelkema, R. (author), Grozema, F.C. (author), van der Zant, H.S.J. (author)We present a method to fabricate insulated gold mechanically controlled break junctions (MCBJ) by coating the metal with a thin layer of aluminum oxide using plasma enhanced atomic layer deposition. The Al<sub>2</sub>O<sub>3</sub> thickness deposited on the MCBJ devices was varied from 2 to 15 nm to test the suppression of leakage currents in...journal article 2016