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Quantum computing architectures have been transferred from the laboratory environment to full-scale introduction to the market for universal quantum computers. INGUN has helped to develop an interconnect solution which replaces traditional bond wiring. This has paved the way for scalability at the Institute of Quantum Computing in Waterloo, ON, Canada.

Explained simply, quantum computing can process much more data than traditional computing systems, which is vital for IT forensics, security and cryptology, for example, making it effective for real world applications and not just in the laboratory. In a binary system, each bit is either a 0 or a 1, and it can never be both 0 and 1, but quantum bits (qubits) allow for a superposition of both states at the same time, which means that more computations can be done when compared to regular binary systems.

A quantum socket, consisting of several resonators is the device under test (DUT) for this application. The RF probes stay permanently in the chuck, but only make contact with the resonator if the chuck is compressed. This is all done at very low temperatures—for this application, an apparatus that cools down the temperature to just slightly above absolute zero (0°K or ‐273.15°C) is used. This is done in several stages. The chuck can be seen in Figure 1.

Figure 1

Figure 1 The HFS-847 301 038 A 1200 M-S-Y probe resonator chuck.

Around this temperature, the resonators become super-conductive. It goes without saying that regular spring probes and contacts would not work at all in such an environment. However, INGUN has come up with a modified coaxial probe version—the HFS-847 301 038 A 1200 M-S-Y 100 mil probe—that uses special beryllium-copper springs and other proprietary materials so that the probe is usable in that temperature range. For this setup, the probes also have to be strictly non-magnetic.

Usually, a thin nickel layer is used beneath the gold plating. This is done because nickel works as a carrier or adhesive for the gold, which ensures a long life and prevents the gold from chipping off from the base material. It acts as a diffusion stopper. Nickel, however, is ferromagnetic, thereby attracted by magnets, so the plating process has to ensure that not even a slightest amount of nickel is present when the parts are electroplated. After plating a Gaussian chamber is utilized to verify that no nickel residue is present on the probes.

The probes operate from DC to beyond 10 GHz with excellent S-parameter characteristics and can be used for grids down to 100 mil (2.54 mm). The tail end of the probe can be connected to 0.047 in. diameter type coaxial cables through the use of a special snap-in connector type.

The special springs were tested and characterized for their compression at room temperature, in liquid nitrogen (i.e., at a temperature of T ≃ 77°K) and in liquid helium (T ≃ 4.2°K). No noticeable difference was found when comparing the cold springs to springs operating at room temperature. The final configuration with the chuck and the coaxial probes and assemblies which gets used in the freezer is shown in Figure 2.

Figure 2

Figure 2 The chuck and coaxial cables.

Figure 3

Figure 3 Close up of the HFS-847 301 038 A 1200 M-S-Y probe tip and body.

What started as a research project has evolved into the development of a probe that can be used for various industries such as automotive, military, space and aviation. In all these industry segments parts have to be cycled with large temperature swings. Also, the use of 100 percent non-magnetic base materials and the use of an “ecobrass” material makes the HFS-847 301 038 A 1200 M-S-Y very interesting for the medical industry. See Figure 3 for a close-up of this probe.

Lake Wylie, SC


INGUN would like to thank Professor Matteo Mariantoni, Jeremy Bejanin, Thomas McConkey and the whole team at the Institute of Quantum Computing in Waterloo, ON, Canada for their studies with the probe. For anyone interested in the research, the article is titled, “Three-Dimensional Wiring for Extensible Quantum Computing: The Quantum Socket,” and was published in Physical Review Applied, October 2016.