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The first few decades of the previous century have witnessed a revolution in the physical sciences due to the advent of quantum mechanics. Now, a hundred years later, quantum mechanics is about to drive a new revolution in technology. As a matter of fact, quantum mechanical phenomena have already found numerous applications in different areas (metrology, sensing, imaging, etc.). Atomic clocks and superconducting quantum interference devices (used for magnetometry), are just a few examples of commercial quantum devices. Yet these examples can be regarded as basic-level quantum technology. The next step is to exploit the inherent complexity of quantum systems, whose origin lies in the basic principle of superposition, namely the property of a quantum object to be simultaneously in two or more possible states. If we consider the simplest case of a quantum particle, e.g. an electron, with two possible states, say state ‘0’ and state ‘1’, the superposition principle allows for that particle to be in both 0 and 1 at the same time (see Fig. 1 and corresponding caption). In a way, a quantum particle can thus encode much more information than a classical device (e.g. a transistor) with only two possible states. A second key property of quantum particles is their ability to couple among each other without necessarily requiring reciprocal interaction. This property, known as quantum entanglement together with the principle of superposition, forms the key elements of quantum information processing. They result in a naturally built-in parallelism that could be exploited to achieve computational powers unaffordable by any classical computer.

Low temperature electron transport measurements of single electron transistors fabricated in advanced CMOS technology with polysilicon gates not only exhibit clear Coulomb blockade behavior but also show a large number of additional conductance fluctuations in the nonlinear regime. By comparison with simulations these features are quantitatively attributed to the effects of discretely charged islands in the polysilicon gates.