Macroscopic Quantum Coherence as a Test of Quantum Mechanics

Fabio Benatti, G. C. Ghirardi, R. Geassi

A. J. Leggett, Anupam Garg

It is shown that, in the context of an idealized ``macroscopic quantum coherence'' experiment, the predictions of quantum mechanics are incompatible with the conjunction of two general assumptions which are designated ``macroscopic realism'' and ``noninvasive measurability at the macroscopic level.'' The conditions under which quantum mechanics can be tested against these assumptions in a realistic experiment are discussed.

권혁준

C. Cosmelli, Maria Gabriella Castellano, Roberto Leoni +3 more

The observation and study of macroscopic quantum coherence (MQC), i.e. the coherent superposition and evolution of macroscopically distinct quantum states, is of great importance for both our understanding of nature and for quantum engineering, for example in quantum computing. Recently a first indication of MQC in a system of SQUIDs has been indirectly observed by means of spectroscopic techniques. Applications like quantum computing, however, require the manipulation and the observation of the time evolution of the MQC states. We have realized a system of SQUIDs for the study of MQC. Our system, based on trilayer Nb/AlOx/Nb technology, consists of a double rf-SQUID, source of the MQC state, inductively coupled to a non-hysteretic dc-SQUID magnetometer and to a hysteretic dc-SQUID threshold detector, used for the read-out of the magnetic flux state. The magnetometer is used to test and monitor the rf-SQUID behaviour, while the hysteretic dc-SQUID is used to perform fast measurements with a reduced back action on the rf-SQUID. We present measurements performed at 4.2 K and at 20 mK to characterize the single devices and their overall behaviour, and a scheme for the use of a set of SQUIDs as a qubit system.

S. de Martino

Non-classical light in high resolution interferometry, F. Barone et al the MQC experiment to test macroscopic quantum coherence in a squid, C. Cosmelli physical relevance of quantum groups, S. De Martino et al charged particle beam transport - quantum-like description versus classical description, R. Fedele and G. Miele coherent transport in mesoscopic devices, V.M. Ramagliu and A. Tagliacozzo stochastic limit for interacting fermions, V. Mastropietro quantum measurements in microscopic and macroscopic oscillators at finite temperature, R. Onofrio neutral plasma in an electromagnetic trap, G. Torelli Liouville integrability of the Schrodinger equation, G. Vilasi mesoscopic gravitation, L. Viola. (Part contents).

Partha Ghose