Europhys. Lett, 46 (1), pp. 31-37 (1999)
Quantum noise in ideal operational amplifiers
J.-M. Courty, F. Grassia and S. Reynaud
Laboratoire Kastler Brossel, case 74 4 place Jussieu, F-75252 Paris Cedex 05, France
(received 26 November 1998; accepted in final form 18 January 1999)
PACS. 42.50Lc - Quantum fluctuations, quantum noise, and quantum jumps.
PACS. 03.65Bz - Quantum mechanics: Foundations, theory of measurement, miscellaneous theories (including Aharonov-Bohm effect, Bell inequalities, Berry's phase).
PACS. 07.50-e - Electrical and electronic components, instruments and techniques.
We consider a model of quantum measurement built on an ideal operational amplifier operating in the limit of infinite gain, infinite input impedance and null output impedance and with a feedback loop. We evaluate the intensity and voltage noises which have to be added to the classical amplification equations in order to fulfill the requirements of quantum mechanics. We give a description of this measurement device as a quantum network scattering quantum fluctuations from input to output ports.