A13 Quantum Electronics, Photonics and MEMS

Topic

At the boundary between conventional electronics and quantum physics, devices emerge whose operation relies directly on quantum phenomena. LEDs and semiconductor lasers emit light particles when an electron and a hole recombine within the material—a recombination process described by the semiconductor physics model—and the energy (and thus the color) of the emitted light depends directly on the bandgap established by that same model; using this family of devices, different materials allow for coverage ranging from the ultraviolet to the infrared spectrum. Quantum efficiency measures the fraction of injected electrons that are effectively converted into photons capable of escaping the device, and it is a key parameter distinguishing a high-quality lighting LED from a mediocre one.

Micro-electromechanical systems (MEMS) integrate microscopic mechanical structures—such as beams, membranes, or suspended masses capable of vibration or movement—onto the same chip as the control electronics; for instance, the accelerometer built into any smartphone is essentially a suspended microscopic mass whose natural vibration frequency changes measurably when the device accelerates.

Quantum tunneling—a phenomenon where a particle has a non-zero probability of passing through an energy barrier that classical physics would deem impassable—forms the basis for both ultra-high-resolution microscopy instruments and modern quantum processors. The fundamental elements of these processors—superconducting qubits—must operate at temperatures extraordinarily close to absolute zero to prevent thermal noise (as described by the electronic noise model) from destroying the delicate quantum states they maintain. That is why this module—which begins at the boundary between conventional electronics and quantum physics—concludes by showing that this limit is not an abstract frontier: it is, quite concretely, the temperature at which ordinary thermal noise ceases to be a manageable nuisance and instead completely destroys the quantum phenomenon a device needs to preserve in order to function.

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