About me

Hi, I am Adriaan, a Delft trained Quantum Engineer and Co-Founder of Orange Quantum Systems, an OEM that provides test equipment for quantum computing chips.

During my PhD (Cum laude), I have worked on control for superconducting quantum systems [1] in the group of Prof. Leo DiCarlo at QuTech. Besides my scientific work, I made key contributions to the development of the Quantum Infinity, a full-stack quantum computer in the cloud. Before starting my PhD, I was on the executive board of De Kleine Consultant, a student-run non-profit business consultancy where I was responsible for internal affairs.

In my free time, I enjoy sailing, windsurfing, tinkering with software projects, and writing with some over-priced coffee.

Kunstenaars Rol

I maintain the website of the Stichting Kunstenaars Rol. The website is a tribute to three generations of artists: my uncle Hanno, my grandfather Henricus and my great-grandfather Cornelis.

References

[1]

M.A. Rol Control for Programmable Superconducting Quantum Systems PhD dissertation, Delft University of Technology (2020).

Social media

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Google Scholar
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Wiki Data

Recognitions and awards

2020

• IOP trusted reviewer status. This is to certify that Mr Rol has achieved IOP trusted reviewer status in recognition of an exceptionally high level of peer review competency.

2018

• Zurich Instruments Pioneer Award, This prize is designed to recognize the importance of collaboration with our customers and partners, who provide us with valuable feedback and ideas and challenge us to make the best performing and most user-friendly instruments. (1500 CHF prize money)

2017

• Best Paper Award IEEE/ACM international symposium on microarchitecture, 2017 (MICRO-50). Presented to X. Fu, M.A. Rol, C.C. Bultink, J. van Someren, N.Khamassi, I.Ashraf, R.F.L. Vermeulen, J.C. de Sterke, W.J. Vlothuizen, R.N. Schouten, C.G. Almudever, L. DiCarlo, K.Bertels. For their paper An experimental Microarchitecture for a Superconducting Quantum Processor.

• HiPEAC Paper Award. The Steering Committee of the HiPEAC Network of Excellence has awarded a HiPEAC Paper Award for the paper An experimental Microarchitecture for a Superconducting Quantum Processor by X. Fu, M.A. Rol, C.C. Bultink, J. van Someren, N.Khamassi, I.Ashraf, R.F.L. Vermeulen, J.C. de Sterke, W.J. Vlothuizen, R.N. Schouten, C.G. Almudever, L. DiCarlo, K.Bertels.

Publications

2023

• Thorsten Last, Massimo Mongillo, Ivanov Tsvetan, Adriaan Rol, Adam Lawrence, Garrelt J. N. Alberts, Danny Wan, Anton Potočnik, and Kristiaan de Greve. Key ingredients for manufacturing superconducting quantum processors at scale. In SPIE Advanced Lithography. 2023. URL: https://spie.org/advanced-lithography/presentation/Key-ingredients-for-manufacturing-superconducting-quantum-processors-at-scale/12497-25.
  [abstract▼] [BibTeX▼]

  Superconducting qubit technology has emerged as a leading candidate for realizing a scalable quantum computing platform. However, current academic approaches in fabrication and testing are not scalable and have started to limit the rapid development of the field. Here we present a strategy based on three key points to move superconducting qubit manufacturing and testing to large-scale fabrication facilities. A foundry-compatible fabrication process of superconducting qubits. Millikelvin cryo-CMOS multiplexer for maximizing cryogenic measurement throughput. And an acceleration in testing through integrated qubit diagnostics and benchmarking tools. A full development cycle will pave the way to commercial quantum advantage.

  @inproceedings{Last_key_2023,
      author = "Last, Thorsten and Mongillo, Massimo and Tsvetan, Ivanov and Rol, Adriaan and Lawrence, Adam and Alberts, Garrelt J. N. and Wan, Danny and Potočnik, Anton and de Greve, Kristiaan",
      title = "Key Ingredients for Manufacturing Superconducting Quantum Processors at Scale",
      options = "useprefix=true",
      year = "2023",
      url = "https://spie.org/advanced-lithography/presentation/Key-ingredients-for-manufacturing-superconducting-quantum-processors-at-scale/12497-25",
      eventtitle = "{{SPIE Advanced Lithography}}",
      booktitle = "{{SPIE Advanced Lithography}}"
  }
  

2022

• Oskar van Deventer, Nicolas Spethmann, Marius Loeffler, Michele Amoretti, Rob van den Brink, Natalia Bruno, Paolo Comi, Noel Farrugia, Marco Gramegna, Andreas Jenet, Ben Kassenberg, Wojciech Kozlowski, Thomas Länger, Tobias Lindstrom, Vicente Martin, Niels Neumann, Homer Papadopoulos, Saverio Pascazio, Momtchil Peev, Richard Pitwon, M. Adriaan Rol, Paolo Traina, Pim Venderbosch, and Frank K. Wilhelm-Mauch. Towards European standards for quantum technologies. EPJ Quantum Technology, 9(1):33, 2022.
  [abstract▼] [BibTeX▼]

  The Second Quantum Revolution facilitates the engineering of new classes of sensors, communication technologies, and computers with unprecedented capabilities. Supply chains for quantum technologies are emerging, some focused on commercially available components for enabling technologies and/or quantum-technologies research infrastructures, others with already higher technology-readiness levels, near to the market.In 2018, the European Commission has launched its large-scale and long-term Quantum Flagship research initiative to support and foster the creation and development of a competitive European quantum technologies industry, as well as the consolidation and expansion of leadership and excellence in European quantum technology research. One of the measures to achieve an accelerated development and uptake has been identified by the Quantum Flagship in its Strategic Research Agenda: The promotion of coordinated, dedicated standardisation and certification efforts.Standardisation is indeed of paramount importance to facilitate the growth of new technologies, and the development of efficient and effective supply chains. The harmonisation of technologies, methodologies, and interfaces enables interoperable products, innovation, and competition, all leading to structuring and hence growth of markets. As quantum technologies mature, the time has come to start thinking about further standardisation needs.This article presents insights on standardisation for quantum technologies from the perspective of the CEN-CENELEC Focus Group on Quantum Technologies (FGQT), which was established in June 2020 to coordinate and support the development of standards relevant for European industry and research.

  @article{deventer_European_2022,
      author = "van Deventer, Oskar and Spethmann, Nicolas and Loeffler, Marius and Amoretti, Michele and van den Brink, Rob and Bruno, Natalia and Comi, Paolo and Farrugia, Noel and Gramegna, Marco and Jenet, Andreas and Kassenberg, Ben and Kozlowski, Wojciech and Länger, Thomas and Lindstrom, Tobias and Martin, Vicente and Neumann, Niels and Papadopoulos, Homer and Pascazio, Saverio and Peev, Momtchil and Pitwon, Richard and Rol, M. Adriaan and Traina, Paolo and Venderbosch, Pim and Wilhelm-Mauch, Frank K.",
      title = "Towards {{European}} Standards for Quantum Technologies",
      date = "2022-12-01",
      year = "2022",
      journal = "EPJ Quantum Technology",
      shortjournal = "EPJ Quantum Technol.",
      volume = "9",
      number = "1",
      pages = "33",
      publisher = "{Springer Berlin Heidelberg}",
      issn = "2662-4400, 2196-0763",
      doi = "10.1140/epjqt/s40507-022-00150-1",
      url = "https://epjqt.epj.org/articles/epjqt/abs/2022/01/40507\_2022\_Article\_150/40507\_2022\_Article\_150.html",
      urldate = "2023-02-06",
      issue = "1",
      langid = "english",
      file = "/Users/adriaanrol/Zotero/storage/72CNCR7C/Deventer et al. - 2022 - Towards European standards for quantum technologie.pdf;/Users/adriaanrol/Zotero/storage/6EZ38SDW/40507\_2022\_Article\_150.html"
  }
  

2021

• Yvonne Y. Gao, M. Adriaan Rol, Steven Touzard, and Chen Wang. Practical guide for building superconducting quantum devices. PRX Quantum, 2:040202, Nov 2021.
  [abstract▼] [BibTeX▼]

  Quantum computing offers a powerful new paradigm of information processing that has the potential to transform a wide range of industries. In the pursuit of the tantalizing promises of a universal quantum computer, a multitude of new knowledge and expertise has been developed, enabling the construction of novel quantum algorithms as well as increasingly robust quantum hardware. In particular, we have witnessed rapid progress in the circuit quantum electrodynamics (cQED) technology, which has emerged as one of the most promising physical systems that is capable of addressing the key challenges in realizing full-stack quantum computing on a large scale. In this Tutorial, we present some of the most crucial building blocks developed by the cQED community in recent years and a précis of the latest achievements towards robust universal quantum computation. More importantly, we aim to provide a synoptic outline of the core techniques that underlie most cQED experiments and offer a practical guide for a novice experimentalist to design, construct, and characterize their first quantum device.

  @article{gao_practical_2021,
      author = "Gao, Yvonne Y. and Rol, M. Adriaan and Touzard, Steven and Wang, Chen",
      title = "Practical Guide for Building Superconducting Quantum Devices",
      journal = "PRX Quantum",
      volume = "2",
      issue = "4",
      pages = "040202",
      numpages = "48",
      year = "2021",
      month = "Nov",
      publisher = "American Physical Society",
      doi = "10.1103/PRXQuantum.2.040202",
      url = "https://link.aps.org/doi/10.1103/PRXQuantum.2.040202"
  }
  

• Garrelt J. N. Alberts, M. Adriaan Rol, Thorsten Last, Benno W. Broer, Cornelis C. Bultink, Matthijs S. C. Rijlaarsdam, and Amber E. Van Hauwermeiren. Accelerating quantum computer developments. EPJ Quantum Technology, 8(1):18, July 2021.
  [abstract▼] [BibTeX▼]

  Product development: Given the recent breakthroughs in quantum technology development in R& D labs all over the world, the perspective of high-tech companies has changed. Product development is initiated next to the existing research and technology development activities.

  Quantum computer product roadmap: Considering the quantum computer as a product requires standardization and integration of all its building blocks and a mature supply chain that can provide high-quality components and can ensure security of supply. The product development approach puts focus on functionality and performance requirements of the product and uses state-of-the-art technology to build the product. Based on the expected requirements of future products it is possible to outline a product development roadmap. It is expected that a fully functional quantum computer will be available within a decade from now, and will be used by the High Performance Computing (HPC) market, where it will replace (part of ) the supercomputers that are currently used for complex calculations and data management. In the short term, a partly functional quantum computer will be available and of interest to the R&D market, which has a need for such a product to expedite their quantum technology developments.

  ImpaQT project: In this paper, we present the product development approach and roadmap for quantum computers, based on superconducting circuits as an example. A group of companies in the Dutch quantum ecosystem (Quantum Delta) have joined forces and have started the ImpaQT project. The companies of the ImpaQT consortium form a local supply chain for key components of quantum computers. This paper shows that quantum community has reached the next level of maturity and that the quantum computer as a commercial product looks set to become a reality.

  @article{alberts_accelerating_2021,
      author = "Alberts, Garrelt J. N. and Rol, M. Adriaan and Last, Thorsten and Broer, Benno W. and Bultink, Cornelis C. and Rijlaarsdam, Matthijs S. C. and Van Hauwermeiren, Amber E.",
      title = "Accelerating quantum computer developments",
      volume = "8",
      issn = "2662-4400, 2196-0763",
      url = "https://epjquantumtechnology.springeropen.com/articles/10.1140/epjqt/s40507-021-00107-w",
      doi = "10.1140/epjqt/s40507-021-00107-w",
      language = "en",
      number = "1",
      journal = "EPJ Quantum Technology",
      month = "July",
      year = "2021",
      pages = "18"
  }
  

• R. Sagastizabal, S. P. Premaratne, B. A. Klaver, M. A. Rol, V. Negîrneac, M. S. Moreira, X. Zou, S. Johri, N. Muthusubramanian, M. Beekman, C. Zachariadis, V. P. Ostroukh, N. Haider, A. Bruno, A. Y. Matsuura, and L. DiCarlo. Variational preparation of finite-temperature states on a quantum computer. npj Quantum Information, 7(1):130, December 2021.
  [abstract▼] [BibTeX▼]

  Abstract 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 thermofield double states using a hybrid quantum-classical variational approach motivated by quantum-approximate optimization algorithms, without prior calculation of optimal variational parameters by numerical simulation. The fidelity of generated states to the thermal-equilibrium state smoothly varies from 99 to 75\% between infinite and near-zero simulated temperature, in quantitative agreement with numerical simulations of the noisy quantum processor with error parameters drawn from experiment.

  @article{sagastizabal_variational_2021,
      author = "Sagastizabal, R. and Premaratne, S. P. and Klaver, B. A. and Rol, M. A. and Negîrneac, V. and Moreira, M. S. and Zou, X. and Johri, S. and Muthusubramanian, N. and Beekman, M. and Zachariadis, C. and Ostroukh, V. P. and Haider, N. and Bruno, A. and Matsuura, A. Y. and DiCarlo, L.",
      title = "Variational preparation of finite-temperature states on a quantum computer",
      volume = "7",
      issn = "2056-6387",
      url = "https://www.nature.com/articles/s41534-021-00468-1",
      doi = "10.1038/s41534-021-00468-1",
      language = "en",
      number = "1",
      journal = "npj Quantum Information",
      month = "December",
      year = "2021",
      pages = "130"
  }
  

• N. Khammassi, I. Ashraf, J. V. Someren, R. Nane, A. M. Krol, M. A. Rol, L. Lao, K. Bertels, and C. G. Almudever. OpenQL: a portable quantum programming framework for quantum accelerators. J. Emerg. Technol. Comput. Syst., dec 2021.
  [abstract▼] [BibTeX▼]

  With the potential of quantum algorithms to solve intractable classical problems, quantum computing is rapidly evolving, and more algorithms are being developed and optimized. Expressing these quantum algorithms using a high-level language and making them executable on a quantum processor while abstracting away hardware details is a challenging task. First, a quantum programming language should provide an intuitive programming interface to describe those algorithms. Then a compiler has to transform the program into a quantum circuit, optimize it, and map it to the target quantum processor respecting the hardware constraints such as the supported quantum operations, the qubit connectivity, and the control electronics limitations. In this article, we propose a quantum programming framework named OpenQL, which includes a high-level quantum programming language and its associated quantum compiler. We present the programming interface of OpenQL, we describe the different layers of the compiler and how we can provide portability over different qubit technologies. Our experiments show that OpenQL allows the execution of the same high-level algorithm on two different qubit technologies, namely superconducting qubits and Si-Spin qubits. Besides the executable code, OpenQL also produces an intermediate quantum assembly code, which is technology independent and can be simulated using the QX simulator.

  @article{Khammassi_openql_2021,
      author = "Khammassi, N. and Ashraf, I. and Someren, J. V. and Nane, R. and Krol, A. M. and Rol, M. A. and Lao, L. and Bertels, K. and Almudever, C. G.",
      title = "Open{Q}{L}: A Portable Quantum Programming Framework for Quantum Accelerators",
      year = "2021",
      issue_date = "January 2022",
      publisher = "Association for Computing Machinery",
      address = "New York, NY, USA",
      volume = "18",
      number = "1",
      issn = "1550-4832",
      url = "https://doi.org/10.1145/3474222",
      doi = "10.1145/3474222",
      journal = "J. Emerg. Technol. Comput. Syst.",
      month = "dec",
      articleno = "13",
      numpages = "24",
      keywords = "quantum computing, quantum processor, quantum circuit, Quantum compiler"
  }
  

2020

• M. A. Rol. Control for programmable superconducting quantum systems. PhD Dissertation, Delft University of Technology, 2020.
  [abstract▼] [BibTeX▼]

  The discovery of quantum mechanics in the 20th century forms the basis of many of the technologies that define our lives today. The ability to engineer and manipulate individual quantum systems – even create artificial atoms – promises a similar revolutionary leap in technology. A quantum technology of particular interest is quantum computing, which has the potential to solve problems that are intractable for classical computers, opening up new domains of computation.

  Meanwhile, an attractive approach to creating engineered quantum systems is circuit quantum electrodynamics (cQED). Where research initially focused on understanding the physics of cQED devices, focus has shifted to building systems capable of performing useful computations. However, this remains extremely challenging, in part due to the inherently fragile nature of the individual quantum bits, but also due to difficulties in controlling and scaling up these systems.

  This thesis focuses on the control aspects of building an extensible full-stack quantum computer based on superconducting transmon qubits. We define the demonstration of quan- tum fault-tolerance as our target application to give focus to our efforts. The QuSurf architecture for a full-stack quantum computer presented in this thesis is designed with this application in mind. We provide a detailed study of the error sources present in this system and give an overview of the relevant characterization techniques.

  In the second part of this thesis, we address several key challenges in the control of a quantum computer.

  To realize high-fidelity coherence limited gates, we present a novel tuneup protocol that achieves a tenfold speedup over the state-of-the-art. This is realized by eliminating the need for qubit initialization. We demonstrate this protocol by calibrating single-qubit gates to a coherence limited Clifford fidelity of 99.9% in one minute.

  Performing repeated parity checks, as is required for quantum error correction, requires reusing qubits quickly after they have been measured. By introducing a numerically optimized depletion pulse we are able to speeds up the depletion of measurement photons in a readout resonator without having to rely on specific symmetry conditions. Using this technique speed up photon depletion by more than six inverse resonator linewidths, reducing the error rate in an emulated ancilla parity check by a factor 75.

  Flux-pulsing based two-qubit gates are the fastest two-qubit gates. However, they are also very technically demanding. The key challenge in performing these gates is addressing the distortions that control signals experience as they traverse various electrical components. We have developed Cryoscope (short for cryogenic oscilloscope) to characterize and correct these distortions. Cryoscope is an in-situ technique that uses the qubit to sample control pulses of arbitrary shape. Even when correcting distortions to within 0.1% two-qubit gates are history-dependent due to the long timescale upon which some of these distortions act. We have invented Net-Zero, a new type of flux-pulsing based two-qubit gate, to address this problem. It makes use of a symmetry condition of the transmon to have net-zero integral, making the gate resilient to long-timescale distortions. The gate suppresses leakage out of the computational subspace to 0.1% by making use of leakage interference and has a built- in echo effect that enhances the coherence of the gate, achieving a two-qubit gate fidelity of 99.1%.

  Custom software is required to perform the physics experiments needed to build and operate a quantum computer. PycQED is an open-source software framework we have developed for this purpose. We discuss the design choices and concepts of PycQED before turning our focus to characterization and calibration. Here we introduced dependency graphs as a useful abstraction and system emulation as an essential development tool for automating the characterization and calibration process.

  We conclude the thesis by reflecting on the limitations of our architecture and providing an outlook on the grand challenges of building a useful kilo-qubit sized quantum computer. We define these challenges as The Application Problem, The Fabrication Problem, and The Calibration Problem.

  @phdthesis{Rol20_thesis,
      Author = "Rol, M. A.",
      School = "Delft University of Technology",
      Title = "Control for Programmable Superconducting Quantum Systems",
      Type = "Ph{D} {D}issertation",
      Year = "2020",
      ISBN = "978-90-8593-451-6",
      SERIES = "Casimir PhD series, Delft-Leiden (2020-25)",
      url = "https://doi.org/10.4233/uuid:0a2ba212-f6bf-4c64-8f3d-b707f1e44953"
  }
  

• M. A. Rol, L. Ciorciaro, F. K. Malinowski, B. M. Tarasinski, R. E. Sagastizabal, C. C. Bultink, Y. Salathe, N. Haandbaek, J. Sedivy, and L. DiCarlo. Time-domain characterization and correction of on-chip distortion of control pulses in a quantum processor. Applied Physics Letters, 116(5):054001, 2020.
  [abstract▼] [BibTeX▼]

  We introduce Cryoscope, a method for sampling on-chip baseband pulses used to dynamically control qubit frequency in a quantum processor. We specifically use Cryoscope to measure the step response of the dedicated flux control lines of two-junction transmon qubits in circuit QED processors with the temporal resolution of the room-temperature arbitrary waveform generator producing the control pulses. As a first application, we iteratively improve this step response using optimized real-time digital filters to counter the linear-dynamical distortion in the control line, as needed for high-fidelity repeatable one- and two-qubit gates based on dynamical control of qubit frequency.

  @article{Rol20,
      author = "Rol, M. A. and Ciorciaro, L. and Malinowski, F. K. and Tarasinski, B. M. and Sagastizabal, R. E. and Bultink, C. C. and Salathe, Y. and Haandbaek, N. and Sedivy, J. and DiCarlo, L.",
      title = "Time-domain characterization and correction of on-chip distortion of control pulses in a quantum processor",
      journal = "Applied Physics Letters",
      volume = "116",
      number = "5",
      pages = "054001",
      year = "2020",
      doi = "10.1063/1.5133894",
      URL = "https://doi.org/10.1063/1.5133894"
  }
  

• C. C. Bultink, T. E. O'Brien, R. Vollmer, N. Muthusubramanian, M. W. Beekman, M. A. Rol, X. Fu, B. Tarasinski, V. Ostroukh, B. Varbanov, A. Bruno, and L. DiCarlo. Protecting quantum entanglement from leakage and qubit errors via repetitive parity measurements. Science Advances, 2020.
  [abstract▼] [BibTeX▼]

  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 computational space. Leakage affects leading experimental platforms, based on trapped ions and superconducting circuits, which use effective qubits within many-level physical systems. We investigate how two-transmon entangled states evolve under repeated parity measurements and demonstrate the use of hidden Markov models to detect leakage using only the record of parity measurement outcomes required for QEC. We show the stabilization of Bell states over up to 26 parity measurements by mitigating leakage using postselection and correcting qubit errors using Pauli-frame transformations. Our leakage identification method is computationally efficient and thus compatible with real-time leakage tracking and correction in larger quantum processors.

  @article{Bultink20,
      author = "Bultink, C. C. and O'Brien, T. E. and Vollmer, R. and Muthusubramanian, N. and Beekman, M. W. and Rol, M. A. and Fu, X. and Tarasinski, B. and Ostroukh, V. and Varbanov, B. and Bruno, A. and DiCarlo, L.",
      title = "Protecting quantum entanglement from leakage and qubit errors via repetitive parity measurements",
      volume = "6",
      number = "12",
      year = "2020",
      doi = "10.1126/sciadv.aay3050",
      publisher = "American Association for the Advancement of Science",
      URL = "https://advances.sciencemag.org/content/6/12/eaay3050",
      eprint = "https://advances.sciencemag.org/content/6/12/eaay3050.full.pdf",
      journal = "Science Advances"
  }
  

• X. Zou, S. P. Premaratne, M. A. Rol, S. Johri, V. Ostroukh, D. J. Michalak, R. Caudillo, J. S. Clarke, L. DiCarlo, and A. Y. Matsuura. Enhancing a near-term quantum accelerator’s instruction set architecture for material science applications. IEEE Transactions on Quantum Engineering, 1:1–7, 2020.
  [abstract▼] [BibTeX▼]

  Quantum computers with tens to hundreds of noisy qubits are being developed today. To be useful for real-world applications, we believe that these near-term systems cannot simply be scaled-down non-error-corrected versions of future fault-tolerant large-scale quantum computers. These near-term systems require specific architecture and design attributes to realize their full potential. To efficiently execute an algorithm, the quantum coprocessor must be designed to scale with respect to qubit number and to maximize useful computation within the qubits’ decoherence bounds. In this work, we employ an application-system-qubit co-design methodology to architect a near-term quantum coprocessor. To support algorithms from the real-world application area of simulating the quantum dynamics of a material system, we design a (parameterized) arbitrary single-qubit rotation instruction and a two-qubit entangling controlled-Z instruction. We introduce dynamic gate set and paging mechanisms to implement the instructions. To evaluate the functionality and performance of these two instructions, we implement a two-qubit version of an algorithm to study a disorder-induced metal-insulator transition and run 60 random instances of it, each of which realizes one disorder configuration and contains 40 two-qubit instructions (or gates) and 104 single-qubit instructions. We observe the expected quantum dynamics of the time-evolution of this system.

  @article{Zou20,
      author = "Zou, X. and Premaratne, S. P. and Rol, M. A. and Johri, S. and Ostroukh, V. and Michalak, D. J. and Caudillo, R. and Clarke, J. S. and DiCarlo, L. and Matsuura, A. Y.",
      doi = "10.1109/TQE.2020.2965810",
      url = "https://ieeexplore.ieee.org/abstract/document/8972540",
      volume = "1",
      issue = "1",
      pages = "1--7",
      title = "Enhancing a Near-Term Quantum Accelerator’s Instruction Set Architecture for Material Science Applications",
      journal = "IEEE Transactions on Quantum Engineering",
      year = "2020"
  }
  

2019

• X. Fu, L. Riesebos, M. A. Rol, J. van Straten, J. van Someren, N. Khammassi, I. Ashraf, R. F. L. Vermeulen, V. Newsum, K. K. L. Loh, J. C. de Sterke, W. J. Vlothuizen, R. N. Schouten, C. G. Almudever, L. DiCarlo, and K. Bertels. eQASM: an executable quantum instruction set architecture. In Proceedings of 25th IEEE International Symposium on High-Performance Computer Architecture (HPCA), 224–237. IEEE, 2019. URL: https://arxiv.org/abs/1808.02449.
  [abstract▼] [BibTeX▼]

  A widely-used quantum programming paradigm comprises of both the data flow and control flow. Existing quantum hardware cannot well support the control flow, significantly limiting the range of quantum software executable on the hardware. By analyzing the constraints in the control microarchitecture, we found that existing quantum assembly languages are either too high-level or too restricted to support comprehensive flow control on the hardware. Also, as observed with the quantum microinstruction set QuMIS, the quantum instruction set architecture (QISA) design may suffer from limited scalability and flexibility because of microarchitectural constraints. It is an open challenge to design a scalable and flexible QISA which provides a comprehensive abstraction of the quantum hardware. In this paper, we propose an executable QISA, called eQASM, that can be translated from quantum assembly language (QASM), supports comprehensive quantum program flow control, and is executed on a quantum control microarchitecture. With efficient timing specification, single-operation-multiple-qubit execution, and a very-long-instruction-word architecture, eQASM presents better scalability than QuMIS. The definition of eQASM focuses on the assembly level to be expressive. Quantum operations are configured at compile time instead of being defined at QISA design time. We instantiate eQASM into a 32-bit instruction set targeting a seven-qubit superconducting quantum processor. We validate our design by performing several experiments on a two-qubit quantum processor.

  @inproceedings{Fu19,
      author = "Fu, X. and Riesebos, L. and Rol, M. A. and van Straten, J. and van Someren, J. and Khammassi, N. and Ashraf, I. and Vermeulen, R. F. L. and Newsum, V. and Loh, K. K. L. and de Sterke, J. C. and Vlothuizen, W. J. and Schouten, R. N. and Almudever, C. G. and DiCarlo, L. and Bertels, K.",
      title = "{eQASM}: An Executable Quantum Instruction Set Architecture",
      booktitle = "Proceedings of 25th IEEE International Symposium on High-Performance Computer Architecture (HPCA)",
      pages = "224--237",
      year = "2019",
      organization = "IEEE",
      url = "https://arxiv.org/abs/1808.02449"
  }
  

• R. Sagastizabal, X. Bonet-Monroig, M. Singh, M. A. Rol, C. C. Bultink, X. Fu, C. H. Price, V. P. Ostroukh, N. Muthusubramanian, A. Bruno, M. Beekman, N. Haider, T. E. O'Brien, and L. DiCarlo. Error Mitigation by Symmetry Verification on a Variational Quantum Eigensolver. Physical Review A, 100:010302(R), 2019.
  [abstract▼] [BibTeX▼]

  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 hydrogen molecule. A finely adjustable exchange interaction between two qubits in a circuit QED processor efficiently prepares variational ansatz states in the single-excitation subspace respecting the parity symmetry of the qubit-mapped Hamiltonian. Symmetry verification improves the energy and state estimates by mitigating the effects of qubit relaxation and residual qubit excitation, which violate the symmetry. A full-density-matrix simulation matching the experiment dissects the contribution of these mechanisms from other calibrated error sources. Enforcing positivity of the measured density matrix via scalable convex optimization correlates the energy and state estimate improvements when using symmetry verification, with interesting implications for determining system properties beyond the ground-state energy.

  @article{Sagastizabal19,
      Author = "Sagastizabal, R. and Bonet-Monroig, X. and Singh, M. and Rol, M. A. and Bultink, C. C. and Fu, X. and Price, C. H. and Ostroukh, V. P. and Muthusubramanian, N. and Bruno, A. and Beekman, M. and Haider, N. and O'Brien, T. E. and DiCarlo, L.",
      Title = "{Error Mitigation by Symmetry Verification on a Variational Quantum Eigensolver}",
      Journal = "Physical Review A",
      url = "https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.010302",
      arxivId = "1902.11258",
      volume = "100",
      pages = "010302(R)",
      year = "2019"
  }
  

• M. A. Rol, F. Battistel, F. K. Malinowski, C. C. Bultink, B. M. Tarasinski, R. Vollmer, N. Haider, N. Muthusubramanian, A. Bruno, B. M. Terhal, and L. DiCarlo. Fast, high-fidelity conditional-phase gate exploiting leakage interference in weakly anharmonic superconducting qubits. Physical Review Letters, 123:120502, 2019.
  [abstract▼] [BibTeX▼]

  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 enhance fidelity (99.1%) and is robust to long-timescale distortion in the flux-control line, ensuring repeatability. Numerical simulations matching experiment show that fidelity is limited by high-frequency dephasing and leakage by short-timescale distortion.

  @article{Rol19_NetZero,
      Author = "Rol, M. A. and Battistel, F. and Malinowski, F. K. and Bultink, C. C. and Tarasinski, B. M. and Vollmer, R. and Haider, N. and Muthusubramanian, N. and Bruno, A. and Terhal, B. M. and DiCarlo, L.",
      Title = "Fast, High-Fidelity Conditional-Phase Gate Exploiting Leakage Interference in Weakly Anharmonic Superconducting Qubits",
      journal = "Physical Review Letters",
      volume = "123",
      pages = "120502",
      year = "2019",
      url = "https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.120502",
      arxivId = "1903.02492"
  }
  

2018

• F. Luthi, T. Stavenga, O.W. Enzing, A. Bruno, C. Dickel, N. K. Langford, M. A. Rol, T.S. Jespersen, F. Nygård, P. Krogstrup, and L. DiCarlo. Evolution of nanowire transmon qubits and their coherence in a magnetic field. Physical Review Letters, 120(10):100502, 2018.
  [abstract▼] [BibTeX▼]

  We present an experimental study of flux- and gate-tunable nanowire transmons with state-of-the-art relaxation time allowing quantitative extraction of flux and charge noise coupling to the Josephson energy. We evidence coherence sweet spots for charge, tuned by voltage on a proximal side gate, where first order sensitivity to switching two-level systems and background 1/f noise is minimized. Next, we investigate the evolution of a nanowire transmon in a parallel magnetic field up to 70 mT, the upper bound set by the closing of the induced gap. Several features observed in the field dependence of qubit energy relaxation and dephasing times are not fully understood. Using nanowires with a thinner, partially covering Al shell will enable operation of these circuits up to 0.5 T, a regime relevant for topological quantum computation and other applications.

  @article{Luthi18,
      author = "Luthi, F. and Stavenga, T. and Enzing, O.W. and Bruno, A. and Dickel, C. and Langford, N. K. and Rol, M. A. and Jespersen, T.S. and Nyg{\aa}rd, F. and Krogstrup, P. and DiCarlo, L.",
      title = "Evolution of nanowire transmon qubits and their coherence in a magnetic field",
      journal = "Physical Review Letters",
      url = "https://doi.org/10.1103/PhysRevLett.120.100502",
      volume = "120",
      number = "10",
      pages = "100502",
      year = "2018",
      publisher = "APS"
  }
  

• C. Pfister, M. A. Rol, A. Mantri, M. Tomamichel, and S. Wehner. Capacity estimation and verification of quantum channels with arbitrarily correlated errors. Nature Communications, 9(1):27, 2018.
  [abstract▼] [BibTeX▼]

  The central figure of merit for quantum memories and quantum communication devices is their capacity to store and transmit quantum information. Here, we present a protocol that estimates a lower bound on a channel’s quantum capacity, even when there are arbitrarily correlated errors. One application of these protocols is to test the performance of quantum repeaters for transmitting quantum information. Our protocol is easy to implement and comes in two versions. The first estimates the one-shot quantum capacity by preparing and measuring in two different bases, where all involved qubits are used as test qubits. The second verifies on-the-fly that a channel’s one-shot quantum capacity exceeds a minimal tolerated value while storing or communicating data. We discuss the performance using simple examples, such as the dephasing channel for which our method is asymptotically optimal. Finally, we apply our method to a superconducting qubit in experiment.

  @article{Pfister18,
      author = "Pfister, C. and Rol, M. A. and Mantri, A. and Tomamichel, M. and Wehner, S.",
      Doi = "10.1038/s41467-017-00961-2",
      Isbn = "2041-1723",
      Journal = "Nature Communications",
      Number = "1",
      Pages = "27",
      Title = "Capacity estimation and verification of quantum channels with arbitrarily correlated errors",
      Url = "https://doi.org/10.1038/s41467-017-00961-2",
      Volume = "9",
      Year = "2018"
  }
  

2017

• M. A. Rol, C. C. Bultink, T. E. O'Brien, S. R. de Jong, L. S. Theis, X. Fu, F. Luthi, R. F. L. Vermeulen, J. C. de Sterke, A. Bruno, D. Deurloo, R. N. Schouten, F. K. Wilhelm, and L. DiCarlo. Restless tuneup of high-fidelity qubit gates. Physical Review Applied, 7:041001, Apr 2017.
  [abstract▼] [BibTeX▼]

  We present a tuneup protocol for qubit gates with tenfold speedup over traditional methods reliant on qubit initialization by energy relaxation. This speedup is achieved by constructing a cost function for Nelder-Mead optimization from real-time correlation of nondemolition measurements interleaving gate operations without pause. Applying the protocol on a transmon qubit achieves 0.999 average Clifford fidelity in one minute, as independently verified using randomized benchmarking and gate-set tomography. The adjustable sensitivity of the cost function allows the detection of fractional changes in the gate error with a nearly constant signal-to-noise ratio. The restless concept demonstrated can be readily extended to the tuneup of two-qubit gates and measurement operations.

  @article{Rol16,
      author = "Rol, M. A. and Bultink, C. C. and O'Brien, T. E. and de Jong, S. R. and Theis, L. S. and Fu, X. and Luthi, F. and Vermeulen, R. F. L. and de Sterke, J. C. and Bruno, A. and Deurloo, D. and Schouten, R. N. and Wilhelm, F. K. and DiCarlo, L.",
      title = "Restless Tuneup of High-Fidelity Qubit Gates",
      journal = "Physical Review Applied",
      volume = "7",
      issue = "4",
      pages = "041001",
      numpages = "6",
      year = "2017",
      month = "Apr",
      publisher = "American Physical Society",
      doi = "10.1103/PhysRevApplied.7.041001",
      url = "https://link.aps.org/doi/10.1103/PhysRevApplied.7.041001"
  }
  

• X. Fu, M. A. Rol, C. C. Bultink, J. van Someren, N. Khammassi, I. Ashraf, R. F. L. Vermeulen, J. C. de Sterke, W. J. Vlothuizen, R. N. Schouten, C. G. Almudever, L. DiCarlo, and K. Bertels. An experimental microarchitecture for a superconducting quantum processor. In Proceedings of the 50th Annual IEEE/ACM International Symposium on Microarchitecture, MICRO-50 '17, 813–825. New York, NY, USA, 2017. ACM. URL: http://doi.acm.org/10.1145/3123939.3123952, doi:10.1145/3123939.3123952.
  [abstract▼] [BibTeX▼]

  Quantum computers promise to solve certain problems that are intractable for classical computers, such as factoring large numbers and simulating quantum systems. To date, research in quantum computer engineering has focused primarily at opposite ends of the required system stack: devising high-level programming languages and compilers to describe and optimize quantum algorithms, and building reliable low-level quantum hardware. Relatively little attention has been given to using the compiler output to fully control the operations on experimental quantum processors. Bridging this gap, we propose and build a prototype of a flexible control microarchitecture supporting quantum-classical mixed code for a superconducting quantum processor. The microarchitecture is based on three core elements: (i) a codeword-based event control scheme, (ii) queue-based precise event timing control, and (iii) a flexible multilevel instruction decoding mechanism for control. We design a set of quantum microinstructions that allows flexible control of quantum operations with precise timing. We demonstrate the microarchitecture and microinstruction set by performing a standard gate-characterization experiment on a transmon qubit.

  @inproceedings{Fu17,
      author = "Fu, X. and Rol, M. A. and Bultink, C. C. and van Someren, J. and Khammassi, N. and Ashraf, I. and Vermeulen, R. F. L. and de Sterke, J. C. and Vlothuizen, W. J. and Schouten, R. N. and Almudever, C. G. and DiCarlo, L. and Bertels, K.",
      title = "An Experimental Microarchitecture for a Superconducting Quantum Processor",
      booktitle = "Proceedings of the 50th Annual IEEE/ACM International Symposium on Microarchitecture",
      series = "MICRO-50 '17",
      year = "2017",
      isbn = "978-1-4503-4952-9",
      location = "Cambridge, Massachusetts",
      pages = "813--825",
      numpages = "13",
      url = "http://doi.acm.org/10.1145/3123939.3123952",
      doi = "10.1145/3123939.3123952",
      acmid = "3123952",
      publisher = "ACM",
      address = "New York, NY, USA",
      keywords = "QuMA, QuMIS, quantum (micro-) architecture, quantum instruction set architecture (QISA), superconducting quantum processor"
  }
  

2016

• C. C. Bultink, M. A. Rol, T. E. O'Brien, X. Fu, B. C. S. Dikken, C. Dickel, R. F. L. Vermeulen, J. C. de Sterke, A. Bruno, R. N. Schouten, and L. DiCarlo. Active resonator reset in the nonlinear dispersive regime of circuit QED. Physical Review Applied, 6:034008, 2016.
  [abstract▼] [BibTeX▼]

  We present two pulse schemes to actively deplete measurement photons from a readout resonator in the nonlinear dispersive regime of circuit QED. One method uses digital feedback conditioned on the measurement outcome, while the other is unconditional. In the absence of analytic forms and symmetries to exploit in this nonlinear regime, the depletion pulses are numerically optimized using the Powell method. We speed up photon depletion by more than six inverse resonator linewidths, saving approximately 1650 ns compared to depletion by waiting. We quantify the benefit by emulating an ancilla qubit performing repeated quantum-parity checks in a repetition code. Fast depletion increases the mean number of cycles to a spurious error detection event from order 1 to 75 at a 1−μs cycle time.

  @article{Bultink16,
      author = "Bultink, C. C. and Rol, M. A. and O'Brien, T. E. and Fu, X. and Dikken, B. C. S. and Dickel, C. and Vermeulen, R. F. L. and de Sterke, J. C. and Bruno, A. and Schouten, R. N. and DiCarlo, L.",
      title = "Active Resonator Reset in the Nonlinear Dispersive Regime of Circuit {Q}{E}{D}",
      journal = "Physical Review Applied",
      volume = "6",
      pages = "034008",
      numpages = "10",
      year = "2016",
      url = "https://link.aps.org/doi/10.1103/PhysRevApplied.6.034008"
  }
  

• J. Cramer, N. Kalb, M. A. Rol, B. Hensen, M. Markham, D. J. Twitchen, R. Hanson, and T. H. Taminiau. Repeated quantum error correction on a continuously encoded qubit by real-time feedback. Nature Communications, 5:11526, 2016.
  [abstract▼] [BibTeX▼]

  Reliable quantum information processing in the face of errors is a major fundamental and technological challenge. Quantum error correction protects quantum states by encoding a logical quantum bit (qubit) in multiple physical qubits. To be compatible with universal fault-tolerant computations, it is essential that states remain encoded at all times and that errors are actively corrected. Here we demonstrate such active error correction on a continuously protected logical qubit using a diamond quantum processor. We encode the logical qubit in three long-lived nuclear spins, repeatedly detect phase errors by non-destructive measurements, and apply corrections by real-time feedback. The actively error-corrected qubit is robust against errors and encoded quantum superposition states are preserved beyond the natural dephasing time of the best physical qubit in the encoding. These results establish a powerful platform to investigate error correction under different types of noise and mark an important step towards fault-tolerant quantum information processing.

  @article{Cramer16,
      author = "Cramer, J. and Kalb, N. and Rol, M. A. and Hensen, B. and Markham, M. and Twitchen, D. J. and Hanson, R. and Taminiau, T. H.",
      Title = "Repeated quantum error correction on a continuously encoded qubit by real-time feedback",
      Journal = "Nature Communications",
      Pages = "11526",
      url = "https://www.nature.com/articles/ncomms11526",
      Year = "2016",
      Volume = "{5}"
  }
  

• S. Asaad, C. Dickel, S. Poletto, A. Bruno, N. K. Langford, M. A. Rol, D. Deurloo, and L. DiCarlo. Independent, extensible control of same-frequency superconducting qubits by selective broadcasting. npj Quantum Information, 2:16029, 2016.
  [abstract▼] [BibTeX▼]

  A critical ingredient for realising large-scale quantum information processors will be the ability to make economical use of qubit control hardware. We demonstrate an extensible strategy for reusing control hardware on same-frequency transmon qubits in a circuit QED chip with surface-code-compatible connectivity. A vector switch matrix enables selective broadcasting of input pulses to multiple transmons with individual tailoring of pulse quadratures for each, as required to minimise the effects of leakage on weakly anharmonic qubits. Using randomised benchmarking, we compare multiple broadcasting strategies that each pass the surface-code error threshold for single-qubit gates. In particular, we introduce a selective broadcasting control strategy using five pulse primitives, which allows independent, simultaneous Clifford gates on arbitrary numbers of qubits.

  @article{Asaad16,
      Author = "Asaad, S. and Dickel, C. and Poletto, S. and Bruno, A. and Langford, N. K. and Rol, M. A. and Deurloo, D. and DiCarlo, L.",
      Title = "Independent, extensible control of same-frequency superconducting qubits by selective broadcasting",
      Journal = "npj Quantum Information",
      Volume = "2",
      Pages = "16029",
      Year = "2016",
      url = "https://www.nature.com/articles/npjqi201629"
  }