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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Quantum heat engines and refrigerators ： ウィキペディア英語版 Quantum heat engines and refrigerators A quantum heat engine is a device that generates power from the heat flow between hot and cold reservoirs. The operation mechanism of the engine can be described by the laws of quantum mechanics. The first realization of a quantum heat engine was pointed out by Geusic, Schultz-DuBois and Scoville.,〔Geusic J, Schulz-DuBios E, Scovil H. 1959. Three-level masers as heat engines. Phys. Rev. Lett. 2:262〕 showing the connection of efficiency of the Carnot engine and the 3-level maser. Quantum refrigerators share the structure of quantum heat engines with the purpose of pumping heat from a cold to a hot bath consuming power first suggested by Geusic, Bois and Scoville .〔Geusic J, Bois E, De Grasse R, Scovil H. 1959. Three level spin refrigeration and maser action at 1500 mcsec. J. App. Phys. 30:1113〕 When the power is supplied by a laser the process is termed optical pumping or laser cooling, suggested by Weinland and Hench .〔D. J. Wineland and H. Dehmelt, Bull. Am. Phys. Soc. 20, 637 (1975); T. W. Hänsch and A. L. Schawlow, "Cooling of Gases by Laser Radiation," Opt. Commun. 13, 68 (1975); Letokhov, V. S., V. G. Minogin, and B. D. Pavlik. "Cooling and trapping of atoms and molecules by a resonant laser field." Optics Communications 19, no. 1 (1976): 72-75.〕 Surprisingly heat engines and refrigerators can operate up to the scale of a single particle thus justifying the need for a quantum theory temed quantum thermodynamics.〔Alicki, Robert. "The quantum open system as a model of the heat engine." Journal of Physics A: Mathematical and General 12, no. 5 (1979): L103.〕 ==The 3-level amplifier as a quantum heat engine== The three-level-amplifier is the template of a quantum device. It operates by employing a hot and cold bath to maintain population inversion between two energy levels which is used to amplify light by stimulated emission 〔Yariv, Amnon (1989). ''Quantum Electronics'', 3rd ed., Wiley. ISBN 0-471-60997-8〕 The ground state level (1-g) and the excited level (3-h) are coupled to a hot bath of temperature $T\_h$. The energy gap is $\backslash hbar\; \backslash omega\_h\; =\; E\_3-E\_1$ . When the population on the levels equilibrate ::$\backslash frac=e^\}$ where $\backslash hbar=\backslash frac$ is Planck's constant and $k\_b$ is Boltzmann's constant. The cold bath of temperature $T\_c$ couples the ground (1-g) to an intermediate level (2-c) with energy gap $E\_2-E\_1=\backslash hbar\; \backslash omega\_c$. When levels 2-c and 1-g equilibrate then ::$\backslash frac=e^\}$. The device operates as an amplifier when levels (3-h) and (2-c) are coupled to an external field of frequency $\backslash nu$. For optimal resonance conditions $\backslash nu=\backslash omega\_h-\backslash omega\_c$. The efficiency of the amplifier in converting heat to power is the ratio of work output to heat input: ::$\backslash eta=\backslash frac\; =1-\backslash frac$. Amplification of the field is possible only for positive gain (population inversion) $G\; =N\_h-N\_c\; \backslash ge\; 0$. This is equivalent to $\backslash frac\; \backslash ge\; \backslash frac$. Inserting this expression into the efficiency formula leads to: ::$\backslash eta\; =1-\backslash frac\; \backslash le\; 1-\; \backslash frac\; =\; \backslash eta\_c$ where $\backslash eta\_c$is the Carnot cycle efficiency. Equality is obtained under a zero gain condition $G\; =0$. The relation between the quantum amplifier and the Carnot efficiency was first pointed out by Geusic and Scoville.:〔 Reversing the operation driving heat from the cold bath to the hot bath by consuming power constitutes a refrigerator. The efficiency of the refrigerator defined as the coefficient of performance (COP) for the reversed device is: ::$\backslash epsilon\; =\; \backslash frac\; \backslash le\; \backslash frac$ 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quantum heat engines and refrigerators」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.