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Quantum Computing with Superconducting Qubits


Application Description

Superconducting qubits are one of the most promising technologies for the realization of a scalable, fault-tolerant quantum computer. Tremendous progress has been achieved over the past two decades, with major steps forward reported worldwide in university laboratories, governmental institutes and a growing number of private companies. As research and development in this area continue at an ever increasing rate, individual players must focus on their key competencies – chip fabrication and characterization, quantum system operation, qubit control or algorithm design.

Zurich Instruments is committed to providing the world's first commercial Quantum Computing Control System (QCCS) capable of scaling beyond 100 qubits. The QCCS contains the classical hardware and software that are needed to connect physical qubits (such as superconducting circuits) to the higher levels in the quantum stack in which the qubit-agnostic programs are defined.

      What challenges do we help our customers tackle?

      • Qubit control: Achieve maximum fidelity on all typical gates thanks to low-noise, high-bandwidth and stable pulse generation and a powerful, memory-efficient sequencer.
      • Qubit readout: Rely on fast, high-fidelity readout of up to 64 qubits per instrument at low latency and for multiple states.
      • Quantum feedback: Combine qubit control and readout into low-latency feedback – from active reset on a single qubit to system-wide syndrome decoding for error correction codes. 
      • Scalable quantum system control: Operate your control system as a single instrument thanks to global timing synchronization, low-latency communication between instruments and a powerful software interface compatible with leading high-level quantum programming software.

      Measurement Strategies


      The QCCS represents the state of the art for controlling superconducting quantum processors. It provides users with a fully programmable system – comprising the HDAWG, the SHFSG, the SHFQA and the PQSC – that features the LabOne® user interface, the LabOne QCCS Software, and APIs and drivers for the most common frameworks such as QuCoDes and Labber. Crucial capabilities include qubit characterization and initialization, gate execution, multi-qubit readout, and feedback operations.

      Qubit characterization and calibration

      • Job: Find the frequency of each qubit and its readout resonator, characterize the qubit performance, and optimize the single-shot readout fidelity.
      • Features: The SHFQA Quantum Analyzer has dedicated modes for resonator spectroscopy at the speed limit, and for multiplexed qubit readout with multi-state discrimination. Using the same double super-heterodyne frequency conversion as the SHFQA, the SHFSG Signal Generator and its powerful sequencer allow for a linear pulse generation even for ultrafast, single-qubit gates. 
      • Benefits: Take advantage of fast and automated calibration for many qubits thanks to the hardware averaging and execution capabilities. The integrated, linear and broadband frequency conversion guarantees a minimal setup time requiring only a single microwave cable for each control and readout line.

      The characterization and calibration of a large superconducting circuit can be very time-consuming; more important, fast multi-qubit-state output after readout is a must for high-fidelity algorithm execution. With dedicated measurement modes for spectroscopy and multiplexed readout, the SHFQA simplifies the process and outputs digital qubit states directly. The SHFSG, with its extremely linear upconversion, allows for high-fidelity single-qubit gate operation through simple scaling of the output amplitude of a pi-pulse.

        High-fidelity gate operation for quantum computation

        • Job: Optimize the qubit gate fidelity, run complex quantum algorithms with or without error correction and characterize their performance and limitations.
        • Features: The SHFSG Signal Generator covers the full frequency range from DC to 8.5 GHz, enabling it to generate a variety of single- and two-qubit gates. The SHFSG uses a double superheterodyne upconversion technique that ensures low-noise and spurious-free signals for high-fidelity gates while eliminating the need for mixer calibration. The HDAWG multi-channel Arbitrary Waveform Generator has a high output power of 18 dBm and low phase noise: combined with the HDAWG-PC Real-time precompensation option, this means the HDAWG is ideal for flux pulses for high-fidelity two-qubit gates.
        • Benefits: The QCCS is a high-performance product fit for growing ambitions.

        The realization of complex quantum algorithms relies on high-fidelity universal single- and two-qubit gates. In superconducting systems, the fidelity of two-qubit gates can be limited by flux pulse noise or phase noise for parametric two-qubit gates. The excellent noise performance of the HDAWG enables flux pulse gate fidelities of 99.9%, while leakage to higher qubit states can be minimized thanks to the HDAWG-PC Real-Time Precompensation option. The output frequency range of the SHFSG spans from DC to 8.5 GHz, allowing it to generate single-qubit gates as well as cross-resonance and parametric two-qubit gates, all without needing to spend time on mixer calibration.


        Fast feedback for active reset and syndrome decoding

        • Job:  Achieve better algorithm performance through improved qubit initialization and error correction
        • Features: Multi-device communication with low latency is possible through trigger connections for small systems and through ZSync and the PQSC for systems of up to 100 qubits and beyond. The PQSC provides register-forwarding for active reset, ready-made global syndrome decoding, and user-access to the FPGA to allow developing your own error correction codes.
        • Benefits: Real-time qubit discrimination of the SHFQA and real-time decision-making and branching of all our control and readout instruments (SHFQA, SHFSG and HDAWG), synchronized and interfaced through the PQSC, ensure that the most advanced feedback codes can be implemented - from fast active reset for qubit initialization to global syndrome decoding of surface codes.

        Multi-device communication via ZSync through a PQSC, together with the compatibility with high-level quantum programming languages such as Qiskit, make the QCCS a scalable system and the ideal choice for a large superconducting circuit aimed at practical quantum computing.

        The Benefits of Choosing Zurich Instruments

        • Take advantage of the pioneering work carried out by our project partners Prof. Andreas Wallraff (ETH Zurich, Switzerland) and Prof. Leo DiCarlo (TU Delft, The Netherlands), as described in this interview.
        • Benefit from the strong technical support provided by our quantum computing specialists, who count years of first-hand experience working with superconducting qubits.
        • The QCCS stands as a proven solution with a track record of high-quality publications (see below).
        • All experimental stages are taken into account with the QCCS: bring-up, characterization, calibration, and computation.
        • Save time with comprehensive software packages: powerful user interface, virtualized programming progress, and continuous software support and updates (for LabOne and the APIs).
        • Add the QCCS to your roadmap for integrating high-level quantum stack software, e.g. Qiskit.

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        Qubit control for 100 qubits and more

        Zurich Instruments - Qubit control for 100 qubits and more

        HDAWG Real-time precompensation

        AWG Real-time precompensation

        Related Blog Posts

        Related Application Notes

        Zurich Instruments

        Frequency Up-Conversion for Arbitrary Waveform Generators

        Zurich Instruments

        Superconducting Qubit Characterization

        Zurich Instruments

        Active Reset of Superconducting Qubits

        Zurich Instruments

        Bell State Preparation of Superconducting Qubits

        Related Publications

        Bengtsson, A. et al.

        Improved success probability with greater circuit depth for the quantum approximate optimization algorithm

        Phys. Rev. Applied 14, 034010 (2020)

        Rol, M.A. et al.

        Time-domain characterization and correction of on-chip distortion of control pulses in a quantum processor

        Appl. Phys. Lett. 116, 054001 (2020)

        Rol, M.A. et al.

        Fast, high-fidelity conditional-phase gate exploiting leakage interference in weakly anharmonic superconducting qubits

        Phys. Rev. Lett. 123, 120502 (2019)

        Bultink, C.C. et al.

        General method for extracting the quantum efficiency of dispersive qubit readout in circuit QED

        Appl. Phys. Lett. 112, 092601 (2018)

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