Chunyan Shi

Chunyan Shi is an Application Scientist at Zurich Instruments. Previously, she worked as an experimental physicist in quantum metrology with cold atoms and trapped ions and in quantum information with rare-earth ions doped organic crystals in China and Europe. At Zurich Instruments, she likes to discuss customers' applications, especially those related to quantum technologies, and find the best measurement solutions.

AWG Precompensation for High-Fidelity CZ Gates in Transmon Qubits

02.11.2019

High quantum gate fidelity is essential for all quantum hardware platforms. Temporal sensitivity to flux noise and flux pulse distortion can pose major limitations to achieving high fidelity with repeatable two-qubit gates in transmon qubits. In a recent publication, Rol and collaborators demonstrated a fast (40 ns), low-leakage (0.1%), high-fidelity (99.1%) and repeatable conditional phase (CZ) gate [1]. They implemented a bipolar flux pulsing method called Net-Zero (NZ) pulse that helped to suppress the leakage from the computational subspace substantially while reducing the susceptibility to electronic noise on the flux line relative to the unipolar pulse. Arbitrary waveform generators (AWGs) driving flux pulses with a low noise spectral density from 1 kHz up to 100 MHz are needed for high-fidelity gate operation.

Figure 1 shows the 1/f noise of the Zurich Instruments HDAWG from 100 Hz to 100 kHz. It has a significantly better performance compared to competing instruments such as Tektronix's AWG5200. Moreover, the HDAWG has a very low noise floor (≤ -145 dBm/Hz @ > 1 MHz), as discussed in more detail here.

Automating IQ Mixer Calibration on the HDIQ

03.02.2021

As a crucial step in the bring-up of superconducting experiments, IQ mixer calibration normally requires multiple instruments from different parties and manual cabling work. This blog post describes how to use the Zurich Instruments HDIQ, HDAWG and UHFQA (or other UHF instruments) to automate IQ mixer calibration and:

Simplify the calibration routine, thus shortening the system characterization time.
Lower the probability of potential failure due to cable reconnection, thus increasing calibration reliability.

Measurement Setup

To have a clear view of the measurement method, only 1 IQ mixer is introduced. Automation of multi-mixer calibration and switch from mixer calibration to qubit experiment will be introduced at the end of the post. The type of mixer calibration discussed here is done with continuous-wave signals.

The measurement diagram is shown in Figure 1, and all signal sources must use the same reference clock, e.g., the one taken from the UHFQA. The functionalities of the instruments and the RF components in the mixer calibration experiment are as follows:

HDIQ as IQ mixers for frequency up-conversion. The RF signal after IQ mixing will be sent out to the “Calib.” port for mixer calibration and to the “Exp.” port for the qubit experiment controlled by a digital input signal or a host computer via Ethernet.
HDAWG as an IF source generates the I and Q signals with compensation terms.
UHFQA as a spectrum analyzer that takes an input IF signal after frequency down-conversion. Only Signal Input 1 is used for mixer calibration.
LO1 as a microwave source for qubit control.
LO2 as a microwave source for frequency down-conversion at the mixer calibration stage and for qubit readout at the qubit experiment stage.
Coaxial IQ mixer as a tool for frequency down-conversion.