𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Simultaneous measurement of non-commuting observables

✍ Scribed by Armen E. Allahverdyan; Roger Balian; Theo M. Nieuwenhuizen


Book ID
104086547
Publisher
Elsevier Science
Year
2010
Tongue
English
Weight
139 KB
Volume
42
Category
Article
ISSN
1386-9477

No coin nor oath required. For personal study only.

✦ Synopsis


A dynamical model of a quantum measurement process is introduced, where the tested system S, a spin 1 2 , is simultaneously coupled with two apparatuses A and A 0 . Alone, A would measure the component ŝz whereas A 0 alone would measure ŝx . The apparatus A simulates an Ising magnetic dot involving N spins weakly coupled to a bath of phonons at a temperature lower than the Curie point. Initially in its metastable paramagnetic state, A tends to reach either one of its two equilibrium ferromagnetic states, with magnetization ΓΎm F or Γ€m F along z, triggered by its interaction with the z-component ŝz of S. Likewise, A 0 is coupled to the x-component ŝx . The four probabilities of A ΓΎ A 0 depend on the polarizations /s z Γ°0ÞS and /s x Γ°0ÞS of S at the initial time. The counting rates for repeated experiments then determine both /ŝ z Γ°0ÞS and /ŝ x Γ°0ÞS, although the process cannot be regarded as an ideal measurement. Three apparatuses simultaneously coupled to all three components of S provide full information on the initial density matrix of S through repeated runs. The lack of violation of Bell's inequalities by the indications of the apparatuses is discussed.


πŸ“œ SIMILAR VOLUMES


Time-dependent invariants of motion for
✍ C.M. Sarris; A.N. Proto πŸ“‚ Article πŸ“… 2005 πŸ› Elsevier Science 🌐 English βš– 241 KB

Using the generalized Ehrenfest theorem the dynamics of the mean values of a complete set of non-commuting observables (CSNCO) associated to a given Hamiltonian is expressed. We found refined time-dependent invariants of motion (TDIM) for the CSNCO, and associated them with different Lie algebras. W