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Charge Sensing the Parity of an Andreev Molecule

van Driel, D. (author), Roovers, B. (author), Zatelli, F. (author), Bordin, A. (author), Wang, Guanzhong (author), van Loo, N. (author), Wolff, J.C. (author), Mazur, G.P. (author), Kouwenhoven, Leo P. (author), Dvir, T. (author)

The proximity effect of superconductivity on confined states in semiconductors gives rise to various bound states such as Andreev bound states, Andreev molecules, and Majorana zero modes. While such bound states do not conserve charge, their fermion parity is a good quantum number. One way to measure parity is to convert it to charge first,...

journal article 2024

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Shuttling an Electron Spin through a Silicon Quantum Dot Array

Zwerver, A.M.J. (author), Amitonov, S. (author), de Snoo, S.L. (author), Madzik, M.T. (author), Russ, M.F. (author), Sammak, A. (author), Scappucci, G. (author), Vandersypen, L.M.K. (author)

Coherent links between qubits separated by tens of micrometers are expected to facilitate scalable quantum computing architectures for spin qubits in electrically defined quantum dots. These links create space for classical on-chip control electronics between qubit arrays, which can help to alleviate the so-called wiring bottleneck. A...

journal article 2023

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Hotter is Easier: Unexpected Temperature Dependence of Spin Qubit Frequencies

Undseth, B.W. (author), Pietx i Casas, O. (author), Raymenants, E.R. (author), Mehmandoost, M. (author), Madzik, M.T. (author), Philips, S.G.J. (author), de Snoo, S.L. (author), Michalak, D.J. (author), Amitonov, S. (author), Tryputen, L. (author), Paquelet Wuetz, B. (author), Fezzi, V. (author), Degli Esposti, D. (author), Sammak, A. (author), Scappucci, G. (author), Vandersypen, L.M.K. (author)

As spin-based quantum processors grow in size and complexity, maintaining high fidelities and minimizing crosstalk will be essential for the successful implementation of quantum algorithms and error-correction protocols. In particular, recent experiments have highlighted pernicious transient qubit frequency shifts associated with microwave...

journal article 2023

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Simple framework for systematic high-fidelity gate operations

Russ, M.F. (author), Philips, S.G.J. (author), Xue, X. (author), Vandersypen, L.M.K. (author)

Semiconductor spin qubits demonstrated single-qubit gates with fidelities up to 99.9 % benchmarked in the single-qubit subspace. However, tomographic characterizations reveal non-negligible crosstalk errors in a larger space. Additionally, it was long thought that the two-qubit gate performance is limited by charge noise, which couples to the...

journal article 2023

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NetSquid, a NETwork Simulator for QUantum Information using Discrete events

Coopmans, T.J. (author), Knegjens, R.J. (author), Dahlberg, E.A. (author), Maier, D.J. (author), Nijsten, L.M.J. (author), de Oliveira Filho, J.A. (author), Papendrecht, M.N.G. (author), Rabbie, J. (author), Rozpedek, F.D. (author), Skrzypczyk, M.D. (author), Wubben, L.C.J. (author), de Jong, W. (author), Wehner, S.D.C. (author)

In order to bring quantum networks into the real world, we would like to determine the requirements of quantum network protocols including the underlying quantum hardware. Because detailed architecture proposals are generally too complex for mathematical analysis, it is natural to employ numerical simulation. Here we introduce NetSquid, the...

journal article 2021

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Protecting quantum entanglement from leakage and qubit errors via repetitive parity measurements

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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A single-hole spin qubit

Hendrickx, N.W. (author), Lawrie, W.I.L. (author), Petit, L. (author), Sammak, A. (author), Scappucci, G. (author), Veldhorst, M. (author)

Qubits based on quantum dots have excellent prospects for scalable quantum technology due to their compatibility with standard semiconductor manufacturing. While early research focused on the simpler electron system, recent demonstrations using multi-hole quantum dots illustrated the favourable properties holes can offer for fast and scalable...

journal article 2020

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Multiplexed quantum transport using commercial off-the-shelf CMOS at sub-kelvin temperatures

Paquelet Wuetz, B. (author), Bavdaz, P.L. (author), Yeoh, L.A. (author), Schouten, R.N. (author), van der Does, C.H. (author), Tiggelman, M.J. (author), Sabbagh, D. (author), Sammak, A. (author), Almudever, Carmen G. (author), Sebastiano, F. (author), Clarke, J. S. (author), Veldhorst, M. (author), Scappucci, G. (author)

Continuing advancements in quantum information processing have caused a paradigm shift from research mainly focused on testing the reality of quantum mechanics to engineering qubit devices with numbers required for practical quantum computation. One of the major challenges in scaling toward large-scale solid-state systems is the limited input...

journal article 2020

document

Quantum Dots in an InSb Two-Dimensional Electron Gas

Kulesh, I. (author), Ke, C. (author), Thomas, Candice (author), Karwal, S. (author), Möhle, C.M. (author), Metti, Sara (author), Kallaher, Ray (author), Gardner, Geoffrey C. (author), Manfra, Michael J. (author), Goswami, S. (author)

Indium-antimonide (InSb) two-dimensional electron gases (2DEGs) have a unique combination of material properties: high electron mobility, a strong spin-orbit interaction, a large Landé g factor, and a small effective mass. This makes them an attractive platform to explore a variety of mesoscopic phenomena ranging from spintronics to...

journal article 2020

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On-chip integration of Si/SiGe-based quantum dots and switched-capacitor circuits

XU, Y. (author), Unseld, F.K. (author), Corna, A. (author), Zwerver, A.M.J. (author), Sammak, A. (author), Brousse, D. (author), Samkharadze, Nodar (author), Amitonov, S. (author), Veldhorst, M. (author), Scappucci, G. (author), Ishihara, R. (author), Vandersypen, L.M.K. (author)

Solid-state qubits integrated on semiconductor substrates currently require at least one wire from every qubit to the control electronics, leading to a so-called wiring bottleneck for scaling. Demultiplexing via on-chip circuitry offers an effective strategy to overcome this bottleneck. In the case of gate-defined quantum dot arrays, specific...

journal article 2020

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Spin Relaxation Benchmarks and Individual Qubit Addressability for Holes in Quantum Dots

Lawrie, W.I.L. (author), Hendrickx, N.W. (author), van Riggelen, F. (author), Russ, M.F. (author), Petit, L. (author), Sammak, A. (author), Scappucci, G. (author), Veldhorst, M. (author)

We investigate hole spin relaxation in the single- and multihole regime in a 2 × 2 germanium quantum dot array. We find spin relaxation times T1 as high as 32 and 1.2 ms for quantum dots with single- and five-hole occupations, respectively, setting benchmarks for spin relaxation times for hole quantum dots. Furthermore, we investigate qubit...

journal article 2020

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A Scalable Cryo-CMOS Controller for the Wideband Frequency-Multiplexed Control of Spin Qubits and Transmons

Van DIjk, Jeroen Petrus Gerardus (author), Patra, B (author), Xue, X. (author), Samkharadze, Nodar (author), Corna, A. (author), Sammak, A. (author), Scappucci, G. (author), Veldhorst, M. (author), Vandersypen, L.M.K. (author), Charbon-Iwasaki-Charbon, E. (author), Babaie, M. (author), Sebastiano, F. (author)

Building a large-scale quantum computer requires the co-optimization of both the quantum bits (qubits) and their control electronics. By operating the CMOS control circuits at cryogenic temperatures (cryo-CMOS), and hence in close proximity to the cryogenic solid-state qubits, a compact quantum-computing system can be achieved, thus promising...

journal article 2020

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Effect of Quantum Hall Edge Strips on Valley Splitting in Silicon Quantum Wells

Paquelet Wuetz, B. (author), Losert, Merritt P. (author), Tosato, A. (author), Lodari, M. (author), Bavdaz, P.L. (author), Stehouwer, Lucas (author), Sammak, A. (author), Veldhorst, M. (author), Scappucci, G. (author)

We determine the energy splitting of the conduction-band valleys in two-dimensional electrons confined to low-disorder Si quantum wells. We probe the valley splitting dependence on both perpendicular magnetic field B and Hall density by performing activation energy measurements in the quantum Hall regime over a large range of filling factors....

journal article 2020

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Vanishing Zeeman energy in a two-dimensional hole gas

Del Vecchio, P. (author), Lodari, M. (author), Sammak, A. (author), Scappucci, G. (author), Moutanabbir, O. (author)

A clear signature of Zeeman split states crossing is observed in a Landau fan diagram of strained germanium two-dimensional hole gas. The underlying mechanisms are discussed based on a perturbative model yielding a closed formula for the critical magnetic fields. These fields depend strongly on the energy difference between the topmost and...

journal article 2020

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On-chip microwave filters for high-impedance resonators with gate-defined quantum dots

Harvey-Collard, P. (author), Zheng, G. (author), Dijkema, J.J. (author), Samkharadze, Nodar (author), Sammak, A. (author), Scappucci, G. (author), Vandersypen, L.M.K. (author)

Circuit quantum electrodynamics (QED) employs superconducting microwave resonators as quantum buses. In circuit QED with semiconductor quantum-dot-based qubits, increasing the resonator impedance is desirable as it enhances the coupling to the typically small charge dipole moment of these qubits. However, the gate electrodes necessary to form...

journal article 2020

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Ballistic supercurrent discretization and micrometer-long Josephson coupling in germanium

Hendrickx, N.W. (author), Tagliaferri, M.L.V. (author), Kouwenhoven, M. (author), Li, R. (author), Franke, D.P. (author), Sammak, A. (author), Brinkman, A. (author), Scappucci, G. (author), Veldhorst, M. (author)

We fabricate Josephson field-effect transistors in germanium quantum wells contacted by superconducting aluminum and demonstrate supercurrents carried by holes that extend over junction lengths of several micrometers. In superconducting quantum point contacts we observe discretization of supercurrent, as well as Fabry-Pérot resonances,...

journal article 2019

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Optically Coherent Nitrogen-Vacancy Centers in Micrometer-Thin Etched Diamond Membranes

Ruf, M.T. (author), IJspeert, M. (author), van Dam, S.B. (author), de Jong, N. (author), van den Berg, J.H. (author), Evers, G.P.H. (author), Hanson, R. (author)

Diamond membrane devices containing optically coherent nitrogen-vacancy (NV) centers are key to enable novel cryogenic experiments such as optical ground-state cooling of hybrid spin-mechanical systems and efficient entanglement distribution in quantum networks. Here, we report on the fabrication of a (3.4 ± 0.2) μm thin, smooth (surface...

journal article 2019

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Light effective hole mass in undoped Ge/SiGe quantum wells

Lodari, M. (author), Tosato, A. (author), Sabbagh, D. (author), Schubert, M. A. (author), Capellini, G. (author), Sammak, A. (author), Veldhorst, M. (author), Scappucci, G. (author)

We report density-dependent effective hole mass measurements in undoped germanium quantum wells. We are able to span a large range of densities (2.0-11×1011cm-2) in top-gated field effect transistors by positioning the strained buried Ge channel at different depths of 12 and 44 nm from the surface. From the thermal damping of the amplitude of...

journal article 2019

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Experimental error mitigation via symmetry verification in a variational quantum eigensolver

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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Entanglement between a Diamond Spin Qubit and a Photonic Time-Bin Qubit at Telecom Wavelength

Tchebotareva, A. (author), Hermans, S.L.N. (author), Humphreys, P.C. (author), Voigt, D. (author), Harmsma, P.J. (author), Cheng, Lun K. (author), Verlaan, Ad L. (author), Dijkhuizen, Niels (author), De Jong, Wim (author), Dréau, A.E. (author), Hanson, R. (author)

We report on the realization and verification of quantum entanglement between a nitrogen-vacancy electron spin qubit and a telecom-band photonic qubit. First we generate entanglement between the spin qubit and a 637 nm photonic time-bin qubit, followed by photonic quantum frequency conversion that transfers the entanglement to a 1588 nm...

journal article 2019