A single-molecule optical transistor

• Published in: Nature (London) 2009-07, Vol.460 (7251), p.76-80
• Main Authors: Hwang, J., Pototschnig, M., Lettow, R., Zumofen, G., Renn, A., Götzinger, S., Sandoghdar, V.
• Format: Article
• Language: English
• Subjects: Applied sciences; Electric fields; Electronics; Exact sciences and technology; Humanities and Social Sciences; Inventions; Lasers; letter; Molecular electronics, nanoelectronics; Molecules; multidisciplinary; Nanotechnology; Photons; Quantum theory; Science; Science (multidisciplinary); Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Technology application; Transistors
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature08134

Quantum optical transistors Quantum information processing systems and related technologies are likely to involve switching and amplification functions in ultrasmall objects such as nanotubes. In today's electronic devices the transistor performs these functions. A 'quantum age' equivalent of the conventional transistor would, ideally, use photons rather than electrons as information carriers because of their speed and robustness against decoherence. But robustness also stops them being easily controlled. Now a team from optETH and ETH in Zurich demonstrates the realization of a single-molecule optical transistor. In it, a single dye molecule coherently attenuates or amplifies a tightly focused laser beam, depending on the power of a second 'gating' beam. The transistor is the most fundamental building block in present-day technologies. For the purpose of quantum information processing schemes and for the development of a 'quantum computer', photons are attractive information carriers because of their speed and robustness against decoherence. However, their robustness also prevents them from being easily controlled; despite this, experiments now show the realization of a quantum optical transistor. The transistor is one of the most influential inventions of modern times and is ubiquitous in present-day technologies. In the continuing development of increasingly powerful computers as well as alternative technologies based on the prospects of quantum information processing, switching and amplification functionalities are being sought in ultrasmall objects, such as nanotubes, molecules or atoms 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 . Among the possible choices of signal carriers, photons are particularly attractive because of their robustness against decoherence, but their control at the nanometre scale poses a significant challenge as conventional nonlinear materials become ineffective. To remedy this shortcoming, resonances in optical emitters can be exploited, and atomic ensembles have been successfully used to mediate weak light beams 7 . However, single-emitter manipulation of photonic signals has remained elusive and has only been studied in high-finesse microcavities 10 , 11 , 12 , 13 or waveguides 8 , 14 . Here we demonstrate that a single dye molecule can operate as an optical transistor and coherently attenuate or amplify a tightly focused laser beam, depending on the power of a second ‘gating’ beam that controls the degree of population inversion. Such