Quantum computing has tremendous potential to overcome some of the fundamental limitations present in classical information processing. Yet, today's technological limitations in the quality and scaling prevent exploiting its full potential. Quantum computing based on superconducting quantum processing units (QPUs) is among the most promising approaches towards practical quantum advantage. In this article the basic technological approach of IQM Quantum Computers is described covering both the QPU and the rest of the full-stack quantum computer. In particular, the focus is on a 20-qubit quantum computer featuring the Garnet QPU and its architecture, which we will scale up to 150 qubits. We also present QPU and system-level benchmarks, including a median 2-qubit gate fidelity of 99.5 Greenberger-Horne-Zeilinger (GHZ) state.

Ultra‐low‐field MRI uses microtesla fields for signal encoding and sensitive superconducting quantum interference devices for signal detection. Similarly, modern magnetoencephalography (MEG) systems use arrays comprising hundreds of superconducting quantum interference device channels to measure the magnetic field generated by neuronal activity. In this article, hybrid MEG‐MRI instrumentation based on a commercial whole‐head MEG device is described. The combination of ultra‐low‐field MRI and MEG in a single device is expected to significantly reduce coregistration errors between the two modalities, to simplify MEG analysis, and to improve MEG localization accuracy. The sensor solutions, MRI coils (including a superconducting polarizing coil), an optimized pulse sequence, and a reconstruction method suitable for hybrid MEG‐MRI measurements are described. The performance of the device is demonstrated by presenting ultra‐low‐field‐MR images and MEG recordings that are compared with data obtained with a 3T scanner and a commercial MEG device. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.

Over the past several years, many groups have developed both millimeter-wave as well as terahertz imaging systems for concealed weapons detection. Typically, systems operating at the millimetre-wave range benefit from good transmission of these frequencies through common clothing materials, but provide only modest spatial resolving power at distances larger than a few meters for practical aperture sizes (dap < 1 m). Hence, these existing systems fall in the category of anomaly detectors, i.e. they intrinsically lack the performance to discriminate threat items from innocuous objects, such as cell phones, mp3 players and the like. Moreover, the radiometric performance of a passive imager has to be better than 0.5 K per frame for sufficient signal-to-noise ratio. In this joint Euro-American effort, we are developing a passive ~0.3 THz - 1 THz camera demonstrator capable of sub-Kelvin thermal resolution at video frame rates. The cryogen-free system utilizes a linear array of cryogenic antenna-coupled vacuum-bridge microbolometers, coupled to innovative all-reflective conical scanning optics and room temperature read-out electronics. First imaging results from the video rate system will be presented.

Superconducting bolometers have long been used as the work horse technology for terahertz astrophysics. In this paper we describe a system developed for stand-off imaging of concealed weapons and explosives. The system utilizes an array of NbN antenna-coupled vacuum-bridge microbolometers as detectors. The detectors are modular, with 8 pixels incorporated within a single module. The modules are mounted onto the 2 cooling stage of a commercial cryogen-free pulse tube refrigerator with a base temperature of ca. 4 K. The readout of the sensors is carried out with an innovative room-temperature feedback preamplifier that can achieve bolometer noise limited performance when operated at the inflexion point of the voltage-biased bolometer.

The objective of this program is to demonstrate a system capable of passive indoors detection and identification of concealed threat items hidden underneath the clothing of non-cooperative subjects from a stand-off distance of several meters. To meet this difficult task, we are constructing an imaging system utilising superconducting ultrawideband antenna-coupled microbolometers, coupled to innovative room temperature read-out electronics, and operated within a cryogen-free pulse tube refrigerator. Previously, we have demonstrated that these devices are capable of a Noise Equivalent Temperature Difference (NETD) of 125 mK over a pre-detection bandwidth from 0.2-1 THz using a post-detection integration time of 30 ins. Further improvements on our devices are reducing this number to a few tens of mK. Such an exquisite sensitivity is necessary in order to achieve the undoubtedly stringent requirements for low false positive alarm rate combined with high probability of detection dictated by the application. Our technological approach allows for excellent per frame NETD (objective 0.5 K or below at 30 Hz frame rate), and is also amenable to multispectral. (colour) imagery that enhances the discrimination of innocuous objects against real threats. In the paper we present results obtained with an 8-pixel subarray from our linear array of 128 pixels constructed using a modular approach. Two-dimensional imaging will be achieved by the use of conical scanning.

We have measured overpressures needed to nucleate helium-4 crystals at temperatures 2 mK-1.0 K. Distributions of nucleation pressures were recorded using a sensitive capacitive pressure gauge with a resolution of 0.3 μbar. Above 100 mK the median value of the distribution decreased according toT −1/2 as expected for thermal fluctuations. Below 100 mK we observed a crossover to a temperature independent regime.

We have made detailed investigations on spiral growth of c-facets in helium crystals with dislocation densities ∼10 cm−2. Our results at high temperaturesT=100–200 mK agree quite well with the classical parabolic power law for spiral growth, whereas a linear dependence on the driving pressure is observed at 2–20 mK. This is a consequence of the inertia of elementary steps in the situation when damping due to phonons is small. At high velocities, all our data display a tendency to saturation which is interpreted as an indication of step localization at large driving forces.