Аннотация:
Superconducting quantum systems are the key elements for a new field of physics – quantum optics with artificial atoms in the microwave range. The superconducting artificial atoms have a set of energy levels and, therefore, behave like natural ones, allowing to demonstrate phenomena of cavity quantum electrodynamics, quantum state control, single photon emission and many others. Such an “atom” has a number of properties that make it possible to realize the fundamental effects of quantum optics on a chip and observe previously unattainable phenomena. For example, it is easy to obtain a physically strong coupling with other circuit elements such as resonators, open transmission lines, other “atoms”. This allows one to realize the fundamental effects with just a single quantum system (“atom”). We, in particular, realise a series of works on the implementation of the lasing effect on a single artificial atom. This is a current-pumped system – the first experimental realisation of lasing on the artificial atom; a lasing effect with pumping using the Landau-Zener tunnelling; a lasing effect on an atom with a specially designed electromagnetic environment; as well as the lasing effect in an acoustic system, where photons are substituted by phonons. The latest experiment is a breakthrough example of the capabilities of superconducting quantum technologies and one of the few effects of a new direction so far – quantum acoustics. In the experiment, the artificial atom is coupled to a surface acoustic wave (SAW) resonator with the resonant frequency 3.15 GHz. The SAW resonator is formed by Bragg mirrors with metallic stripes and the electric filed is converted to acoustics one by inter-digitated transducers (IDT) – a set of metallic stripes with submicron step on a surface of quartz. By implementing a mechanism of population inversion in the “three-level atom” with the microwave excitation to the third energy level and relaxation to the first excited one. When the atom is in nearly resonant conditions, an emission of radiation is observed. Importantly that the emission linewidth exhibits strong line narrowing by one order of magnitude. The number of phonons, estimated in the resonator is about one hundred.
