A Fast and Integrated Qubit Control System - SHFQC Launch Event

March 18, 2022 by Tobias Thiele

On March 3rd, Jan Benhelm, Bruno Küng and I were thrilled to welcome a diverse audience from all over the world to present our newest instrument - the SHFQC Qubit Controller.

In the first part of the webinar Jan explained how the SHFQC integrates a full qubit control system for up to 6 superconducting qubits in a single instrument, and why it extends the reach of the second generation of our Quantum Computing Control System (QCCS) to small numbers of qubits while also providing value for bigger qubit counts.

I then presented some first measurement successes with the SHFQC in the laboratory: we fully characterized 5 qubits in a short time, operating the instrument with minimal communication overhead and making use of the SHFQC's great analog front-end in combination with high-performance signal processing. Specifically, we demonstrated live:

  • The advantages of the integrated superheterodyne frequency conversion to microwave frequencies.
  • Clean resonator spectroscopy over a 1.4-GHz-wide band operating at the technical speed limit.
  • Clean, wide-band and parallel qubit spectroscopy on 5 qubits, operating at the technical speed limit.
  • Efficient and intuitive programming of single-qubit pulse sequences with pulse-level sequencing.
  • Fast and minimal information transfer to the instrument, exploiting the strengths of pulse-level sequencing, in the case of randomized benchmarking.

For all covered topics, we provided detailed insight into the inner workings of our instruments with functional diagrams and basic code snippets, along with tips and tricks on how to optimally program the devices.

To conclude the presentation, Bruno discussed our approach to fast local feedback using the SHFQC; he also showed how the instrument supports larger system architectures and global feedback protocols to efficiently control systems with 100 qubits and beyond.

If you missed the launch event or would like to watch the video again, the complete recording is available here.

The event ended with a live Q&A session: the answers provided during the session as well as the answers to the questions that could not be answered due to limited time are now summarized below. Do get in touch with us to ask more questions and discuss your application!

 

Are the Jupyter Notebooks presented available somewhere?

The ones we showed aren't, as they were tailored for the live presentation, but we offer a large set of scripts in our publicly available GitHub repository. There you can find examples and drivers for Labber and QuCoDeS as well as our zhinst-toolkit, with many more scripts accompanying our examples, tutorials and blog posts.

If there is a specific experiment that you would like to discuss, please contact us and we will be happy to help!

Are additional features like the scope or the user interface that you showed in your demo included?

Yes, all our instruments come with a GUI and additional features such as a scope or spectrum analyzer without extra costs. We also upgrade our software and firmware on a 6-month basis, so that we can provide you with extra features and performance improvements every time (free of charge, too).

What are your output/input sampling rates? For the parameterized pulse synthesis, at what sampling rate are these pulses synthesized?

6 GSa/s on all outputs and 4 GSa/s on the inputs. Internally, the waveforms can be defined on a 2 GSa/s timing grid. Please find more information in the specifications, or get in touch with us!

You mentioned one can read out up to 16 qubits - what if I only have 3 qubits?

The base version of the SHFQC comes with a quantum analyzer channel equipped with 8 integration weights that can optionally be extended to 16. Even if you work with 3 qubits, more than 3 integration weights are likely to be useful to you, e.g. to optimally detect and correct for leakage to your qubits' f-state level.

How well are the signal generator outputs suited for the control of couplers and to provide signals to flux lines?

The low-frequency (LF) signal path of the signal generator control channels supports pulses from DC up to ~1.5 GHz. The main differences with respect to the outputs of the HDAWG - our recommended instrument for flux pulses around DC - are a reduced output power and the absence of real-time filter functions to precompensate distortions of your signal in your cryostat.

In your full QCCS, how is the clock distributed for the synchronization?

Our ZSync link distributes both the data and the reference clock in a star topology with the PQSC Programmable Quantum System Controller as the central knowledge hub.

What is the latency for global feedback?

The latency through our central controller, i.e., from last sample in to first sample out between any channel in the system, is typically below 530 ns. See our page on quantum feedback for more details on latencies in different configurations.

With the SHFQC, what is the role of the other SHF instruments, the SHFQA and the SHFSG?

Because of the integrated readout channel, the SHFQC is designed to work best with superconducting circuits and related applications and fulfills the needs of small systems with a few qubits. The SHFSG only contains channels to control pulses, and can thus be used in many more applications and on more platforms, including NV centers. Even for superconducting circuits, the SHFSG and the SHFQA may represent a better instrument choice if you plan to scale the number of your qubits - which depends on your chip architecture. As Bruno explained in his part of the presentation, a combination of SHFQAs, SHFSGs, SHFQCs and HDAWGs is most likely to provide the biggest value for a scaling quantum computer.