| DATE: |
2005-06-28 15:00 - |
| PLACE: |
Kenkyu Honkan Rm. 321 |
| TITLE: |
Quantum-state representation with experimental data --- The Bloch vector and its state space for N level systems |
| CONTACT: |
tango |
| SPEAKER: |
Dr. Gen Kimura (Tohoku Univ. Graduate School of Information Sciences) |
| LANGUAGE: |
English |
| ABSTRACT: |
Quantum state is usually represented by wave function or more generally by density matrix, which we do not know directly from experimental data. This does not mean that quantum state can not be represented by purely experimental data like probability or expectation values and there are lots of ideas to describe quantum state with quantities directly available to experimentalists. Needless to say, such representations will be helpful for the direct comprehension of quantum state in connection with experiments. On the other hand, since such ideas give a sort of returns to classical physics, where we represented state with experimental data like position and momentum, one can expect that the strangeness of quantumness might reappear in a different way from usual language (to use density matrix).
One of such representations of quantum state is the Bloch vector, the components of which are expectation values of suitable observables (generators of SU(N)). This notion is quite famous in 2 level systems, but can be easily generalized to any N level system. We concentrate on this and investigate the state space, from both geometrical and analytical point of view. We show some interesting properties which does not appear in 2 level systems, discussing its structual reason and physical meaning.
|
|
