Physicists at Marburg University assign unexpected experimental results to a quantum memory.
Prior to this work, ideal light sources (such as perfect lasers) were thought to emit as much light as excited in them via pumping.
Physicists from Marburg, Dortmund, St. Petersburg, and Notre Dame, USA, investigated optically pumped quantum-dot lasers and demonstrated that the pumping induces a quantum memory between the pump excitation and the light emission. Beating expectations, this quantum-memory was shown to induce intensity oscillations on top of the expected linear output.
Even more striking, these oscillations could be either suppressed or significantly enhanced via the quantum fluctuations of the pump laser. This breakthrough will be published in the coming issue of the journal Physical Review Letters on 15.08.2014.
The theoretical research team led by Professors Mackillo Kira and Stephan W. Koch from the Philipps-Universität Marburg analyzed the unusual experimental results obtained by the team led by Prof. Manfred Bayer. The experimentalists used laser light to excite quantum dots inside a microcavity and carefully recorded the subsequent light emission.
The first author of this publication, M.Sc. Christian Berger, explains “The input pump laser excites the quantum dot to a higher energy level; afterwards, the excitation returns to the ground state by emitting light, defining the output”.
Surprisingly, the authors found that the output intensity does not scale linearly with the input intensity as expected earlier. Instead, the output power was oscillating around its expected value. They could even show that the oscillations can be completely controlled by the quantum-optical fluctuations of the optical pump, which highlights the significance of this extraordinary discovery.
Mackillo Kira elaborates, “We were thrilled after we verified the quantum-optical control of these oscillations which is a genuine property of our quantum-optical spectroscopy concept”. Manfred Bayer continues, “Based on these findings, we could unambiguously identify the observed oscillations as a genuine quantum-memory effect”. Stephan W. Koch explains the origin of the quantum memory, “The light emission remembers the earlier excitation process via quantum memory – this effect is intimately connected with entanglement, which is one of the manifestations of the fundamental quantum weirdness”.
This work is connected with the ongoing effort to convert quantum-world phenomena to tangible applications. The existence of quantum-memory effects and their quantum-optical control may hold the key to developing lasers whose quantum-optical aspects become completely user defined. Such laser sources would be extremely useful in quantum-information science and in quantum spectroscopy which aims to control quantum processes of complex systems via the quantum aspects of light.
Professors Mackillo Kira and Stephan W. Koch teach semiconductor quantum optics and theoretical semiconductor physics at the Philipps-Universität Marburg. In February, they identified a new quasiparticle, the dropleton, with the help of quantum-optical spectroscopy.
Publication: Christian Berger & al.: Quantum-Memory Effects in the Emission of Quantum-Dot Microcavities, Physical Review Letters 2014.
German version of this press release: http://www.uni-marburg.de/aktuelles/news/2014c/quantengedaechtnis
Professor Dr. Mackillo Kira
Field: Theoretical Semiconductor Physics
Phone: 06421 2824222
Dr. Susanne Langer | idw - Informationsdienst Wissenschaft
Streamlining accelerated computing for industry
24.08.2016 | DOE/Oak Ridge National Laboratory
Lehigh engineer discovers a high-speed nano-avalanche
24.08.2016 | Lehigh University
Scientists and engineers striving to create the next machine-age marvel--whether it be a more aerodynamic rocket, a faster race car, or a higher-efficiency jet...
Waveguides are widely used for filtering, confining, guiding, coupling or splitting beams of visible light. However, creating waveguides that could do the same for X-rays has posed tremendous challenges in fabrication, so they are still only in an early stage of development.
In the latest issue of Acta Crystallographica Section A: Foundations and Advances , Sarah Hoffmann-Urlaub and Tim Salditt report the fabrication and testing of...
Electrochemists at TU Graz have managed to use monocrystalline semiconductor silicon as an active storage electrode in lithium batteries. This enables an integrated power supply to be made for microchips with a rechargeable battery.
Small electrical gadgets, such as mobile phones, tablets or notebooks, are indispensable accompaniments of everyday life. Integrated circuits in the interiors...
Recent findings indicating the possible discovery of a previously unknown subatomic particle may be evidence of a fifth fundamental force of nature, according...
A nanocrystalline material that rapidly makes white light out of blue light has been developed by KAUST researchers.
25.08.2016 | Event News
24.08.2016 | Event News
12.08.2016 | Event News
30.08.2016 | Power and Electrical Engineering
30.08.2016 | Life Sciences
30.08.2016 | Life Sciences