The basis of *superconducting qubits* are the energy levels electric, anharmonic oscillators. To explain anharmonic oscillators, let's start with their simpler counterpart, [[Harmonic Oscillator|harmonic oscillators]]. A quantum mechanical, [[Harmonic Oscillator|harmonic oscillator]] is a special system in quantum mechanics: it is one of the few systems that we can solve exactly and it builds the basis for many advanced theories. One of its special properties is the discrete level-spacing with equal gaps between all levels. They can be realized in electronics by [[LC Circuit|LC circuits]], an electric circuit consisting of a [[Capacitor|capacitor]] and an [[Inductor|inductor]]. ![[harmonic_vs_anharmonic_oscillator.excalidraw.light.svg]] However, for a good [[Qubit|qubit]], we would like two levels, that are easily distinguishable. By adding an anharmonicity to the oscillator, we achieve can that: we substitute the coil in the [[LC Circuit|LC circuit]] by a superconducting device, a so-called [[Josephson Junction|Josephson junction]]. This device shifts the levels of the oscillator to have different gaps. By selecting the biggest one between the bottom two levels, we have the two-level system for our [[Qubit|qubit]]. The [[Quantum Information|quantum information]] stored in the electrical circuit can be modified by interactions with [[Microwave Radiation|microwave radiation]], a low-energetic version of light. Since the energy difference are on the energy-scale of thermal fluctuations, these qubits have to cooled down in big fridges to temperature close to [[Absolute Zero Temperature|absolute zero temperature]]. This is technologically challenging and rather costly. >[!read]- Further Reading >- [[Electromagnetism]] >- [[Harmonic Oscillator]] >- [[LC Circuit]] >[!ref]- References