Quantum Computing with Superconducting Qubits

Superconducting quantum computing is one of the most promising technologies for the realization of scalable quantum computers. 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 – qubit fabrication, qubit characterization, or algorithm design.

Zurich Instruments is committed to providing the world's first commercial Quantum Computing Control System (QCCS) capable of scaling to up to 100 qubits. The QCCS contains the hardware and software that are needed to connect physical qubits (such as superconducting circuits) to the higher levels in the quantum stack that define what programs run on the quantum computer.

What challenges do we help our customers tackle?

• Qubit control: extremely low phase noise control pulses with sub-nanosecond time resolution and real-time precompensation for high-fidelity gate operation.
• Qubit readout: fast, high-fidelity readout of multiple qubits and low latency real-time feedback.
• Quantum programming: powerful software interface compatible with leading high-level quantum programming software.
• Scalable quantum computing: system-wide timing synchronization and low-latency communication between instruments.

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 UHFQA and the PQSC – that features the LabOne^® user interface and APIs for Python, C/C++, MATLAB^®, LabVIEW^™ and .NET. Crucial capabilities include qubit characterization and initialization, gate operation, readout, and branching.

Bring-up

• Job: Characterize the noise performance of the amplification chain and optimize it for the best signal-to-noise ratio (SNR).
• Features: The UHF FFT Scope guarantees SSB phase noise below -155 dBc/Hz for noise characterization. Technical support is available for Labber and QCoDeS.
• Benefits: Reduce the complexity of your setup – no need to switch instrumentation between bring-up and other experimental stages.

To optimize the noise performance of amplifiers, a spectrum analyzer with low phase noise is required. With its integrated low-noise FFT scope, the UHFQA Quantum Analyzer is suitable both for bring-up and for subsequent experimental steps. In this way, there is no need for manual reconnection or automated switching. Drivers for Labber and QCoDeS are also fully supported on the QCCS.

Characterization and calibration

• Job: Find each qubit and resonator frequency, calibrate the mixers, characterize the performance of your qubit, and optimize the single-shot readout fidelity.
• Features: Two readout modes of the UHFQA are dedicated to spectroscopy and multiplexed readout. The direct digital qubit output from the UHFQA does not require upload or download of data to or from your computer. Low latency enables fast feedback operation.
• Benefits: Take advantage of fast and automated calibration for scalable superconducting circuits, as well as of quickly updated software features and extensive programming support.

The characterization and calibration of a large superconducting circuit can be very time-consuming; more importantly, fast multi-qubit-state output after readout is a must for conditional feedback operations. With dedicated measurement modes for spectroscopy and multiplexed readout, the UHFQA simplifies the process and outputs digital qubit states directly.

Computation

• Job: Optimize the qubit gate fidelity, run complex quantum algorithms with or without error correction and characterize their performance and limitations.
• Features: The HDAWG multi-channel Arbitrary Waveform Generator outputs at 5 Vpp with low phase noise give access to gate fidelities beyond 99.9%. The HDAWG-PC Real-time Precompensation option helps to minimize leakage to higher qubit states for high-fidelity two-qubit gates. Multi-device communication with low latency is possible through a DIO connection for small systems (1 HDAWG + 1 UHFQA) and through ZSync for systems up to 100 qubits (1 PQSC + n HDAWG + m UHFQA).
• 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. The excellent noise performance of the HDAWG enables gate fidelities of 99.9%, while leakage to higher qubit states can be minimized thanks to the HDAWG-PC Real-Time Precompensation option. Multi-device communication via DIO or Trigger output, 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.