From 14:00

At National University of Science and Technology MISIS

Superconducting Metamaterials Laboratory / smm@misis.ru, +7 (495) 638 46 46

Open Lecture  “Quantum Coherence Through the Relaxation” by Dr. Zoran Ivic (University of Belgrade, “Vinča” Institute of Nuclear Sciences)

Abstract: 

The discovery of quantum coherence (QC) in meso- and macroscopic systems made possible practical applications of quantum mechanical phenomena such as quantum entanglement, superposition, and tunneling in the development of quantum technologies including quantum information processing, communication, and teleportation. Quantum metamaterials (QMM), engineered media built of a large number of the artificial periodically arranged ‘atoms’ (e. g., superconducting qubits), had shown certain promises for the development of photonic quantum information storage devices. The use of ‘meta-atoms‘ made it possible to construct devices operable in the regimes which are not accessible with real atoms. Due to their dimensions, ‘meta-atoms' are exposed to strong environmental influences, causing relaxation, which may destroy quantum coherence. 

There are two main types of relaxation phenomena: homogeneous and inhomogeneous broadening of atomic levels (spectral lines). The first one, homogeneous, corresponds to the situation in which all atoms are indistinguishable. It is called natural broadening and leads to dissipation with damping constant inversely proportional to the natural lifetime of the spectral line. The second type of relaxation, inhomogeneous, corresponds to a situation in which ‘atoms' feel different environments.

Relaxation does not necessarily lead to decoherence. This concerns a lot of cooperative coherent phenomena, emerging when short, very intense, electromagnetic (EM) pulses propagate through the media composed of two-level ‘atoms’. These are Dicke superradiance, self-induced transparency, EM induced transparency and photon echo, for which relaxation, inhomogeneous in particular, is required. On the other hand, homogeneous relaxation is unwanted and should be avoided.

In this lecture, we present the way how the emergence of QC may be achieved by the convenient construction of QMM. Three experimental setups were considered: devices built of charge, flux, and transmon qubits. A brief discussion is presented to elucidate conditions when inhomogeneous broadening supports QC.  Finally, we speak about the use of Dicke superradiance as a mean for the suppression of relaxation.

Venue:

NUST MISIS (Moscow, Lelinsky pr.4), conference hall Б-607 (6th floor)

Language: English