Continuous quantum measurement with observer: pure wavefunction evolution instead of decoherence
Abstract
We consider a continuous measurement of a twolevel system (doubledot) by weakly coupled detector (tunnel point contact nearby). While usual treatment leads to the gradual system decoherence due to the measurement, we show that the knowledge of the measurement result can restore the pure wavefunction at any time (this can be experimentally verified). The formalism allows to write a simple Langevin equation for the random evolution of the system density matrix which is reflected and caused by the stochastic detector output. Gradual wavefunction ``collapse'' and quantum Zeno effect are naturally described by the equation.
 Publication:

arXiv eprints
 Pub Date:
 July 1998
 arXiv:
 arXiv:quantph/9807051
 Bibcode:
 1998quant.ph..7051K
 Keywords:

 Quantum Physics;
 Condensed Matter  Mesoscopic Systems and Quantum Hall Effect
 EPrint:
 6 pages, 2 figures