Simultaneous measurement of non-commuting observables
β 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.
β¦ 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 Εz whereas A 0 alone would measure Εx . 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 Γm F along z, triggered by its interaction with the z-component Εz of S. Likewise, A 0 is coupled to the x-component Εx . The four probabilities of A ΓΎ A 0 depend on the polarizations /s z Γ°0ΓS and /s x Γ°0ΓS of S at the initial time. The counting rates for repeated experiments then determine both /Ε z Γ°0ΓS and /Ε x Γ°0ΓS, 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.
π SIMILAR VOLUMES
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