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Getting from Qubit to Mega-Qubit Quantum Computers with Radio Frequency (RF) Calibrations

Description

Dilution Refrigerator

Each Aspect a Remarkable Accomplishment - Together, a Game Changer1

Credit: Professor Nick McGruer

“Getting from Qubit to Mega-Qubit Quantum Computers with RF Calibrations” is a multi-laboratory effort to develop precision radio frequency measurements in the coldest and darkest places on the planet, cryostats and dilution refrigerators. The projects in this multi-laboratory effort are focused on developing ultrasensitive calibrated cryogenic on-chip microwave measurements that are essential for understanding, designing, testing and scaling the microwave circuits that surround, initialize, control, couple and readout the qubits that are at the core of electrically-based quantum computers.

Modern network analyzers at microwave frequencies are unique and indispensable tools for making measurements, developing accurate models and verifying designs. They characterize scattering parameters, impedances, voltage and current waveforms, nonlinear distortion and noise with a single instrument; the exact capability needed within a dilution refrigerator! This project is devoted to bringing NIST’s expertise regarding these measurement capabilities into cryostats and dilution refrigerators to characterize nonlinear cryogenic devices and microwave signals with many orders of magnitude greater sensitivity than currently possible.

Potential Impact

This project will deliver a network analyzer and on-chip calibration artifacts for electrical phase, power, and noise-parameter calibrations for scaling quantum computing to millions of qubits.

Technical Plan:

NIST is working on developing the world’s most sensitive millikelvin vector network analyzer along with the precision artifacts required to calibrate it, the world’s first millikelvin microwave electrical-phase standard, the world’s most sensitive microwave power sensor and, the world’s first millikelvin microwave variable-impedance load. These projects will revolutionize integrated-circuit test at cryogenic temperatures and promise to lead to fundamental breakthroughs in measurement science.

World’s Most Sensitive Network Analyzer

NIST is working on the development of an ultrasensitive front-end and a fully automated wafer-probing apparatus for direct on-chip measurements from 10 kelvin (K) to millikelvin temperatures. Nearly-quantum-limited parametric amplifiers are placed close to the device reference plane in order to measure the lowest signal and noise levels possible. Success will require developing more robust SQUID and parametric traveling-wave, and reflection amplifiers to improve stability, dynamic range and bandwidth. These improvements will be important not just for this IMS, but for the next generation of multi-qubit readout applications. Impedance and scattering-parameter calibrations will be based on cryogenic on-chip niobium scattering-parameter calibration kits that the group developed previously for use at 4 K.

World’s Most Sensitive Single Instrument Tool Kit
A microphotograph of  a NIST-developed parametric amplifier of the type that will be used to improve the sensitivity of the network analyzer.1
Credit: Professor Nick McGruer

World’s First Millikelvin Electrical-Phase Reference

NIST's focus for this project is on the development of the world’s most sensitive vector network analyzer for on-chip probing. It will be equip to perform scattering-parameter, modulated-signal, nonlinear and noise-parameter measurements. 

Worlds First mK Electrical Phase Standard
A sketch of the electro-optic sampling system being developed to calibrate the electrical phase of the network analyzer.

World’s Most Sensitive Microwave Power Sensor

NIST is investigating two complementary solutions in a high-risk aspect of the project in which microwave power levels used in superconductor and semiconductor-based quantum computing are extremely low, typically six-orders-of-magnitude lower than what current room temperature detectors can measure. These power sensors will have fundamental applications in measurement science and allow rigorous calibration of the network analyzers at cryogenic temperatures over large dynamic ranges.

Worlds Most Sensitive Microwave Power Sensor
A microfabricated power sensor similar to that being developed for use in the dilution refrigerator.

Cryogenic Noise Source and World’s First Controllable Millikelvin Variable-Impedance Microwave Termination

NIST is developing two tools for noise calibration: a calibrated noise source and a variable-impedance load. Because only a few microwave photons can be used to read a Josephson qubit or quantum dot, the noise performance of even the best superconducting components must be carefully optimized to avoid destroying the state of a quantum-computer’s qubits.

To characterize the full noise parameters of cryogenic circuits, which includes information on how to reflect noise at the input of the device to help cancel correlated noise at its output, the group is developing systems to supply different impedances at known millikelvin temperatures at the device’s input based on electrostatically-operated MEMS switches in microwave probes. Current challenges of using commercial MEMS switches include breakage due to differing coefficients of thermal expansion, excessive power dissipation and “stiction” due to freezing gasses.

New Variable Impedance Load
Our millikelvin variable-impedance microwave termination will be based on electrostatic MEMs switches with ultra-low energy dissipation.

 

Publications

A. S. Boaventura et al., "Microwave Characterization of Superconducting Circuits," in Applied Superconductivity Conf., November 2018

C. Su-Wei, J. Aumentado, W. Wei-Ting, and J. C. Bardin, "Noise measurement of cryogenic low noise amplifiers using a tunnel-junction shot-noise source," in IEEE Int. Microw. Symp., 22-27 May 2016, pp. 1-4

 Y. Wang, R. Lewis, R. Radebaugh, M. M. Lin, V. M. Bright, and Y. Lee, "A Monolithic Polyimide Micro Cryogenic Cooler: Design, Fabrication, and Test," J. Microelectromechanical Systems, vol. 23, no. 4, pp. 934-943, 2014

Sources

We appreciate the permissions to use images from Attocube, FormFactor and Rohde & Schwarz USA. NIST does not endorse commercial products. Other products may work as well or better.

Created March 4, 2021, Updated April 29, 2021