The Spin Density Matrix I: General Theory and Exact Master Equations

Details The Spin Density Matrix I: General Theory and Exact Master Equations The Spin Density Matrix I: General Theory and Exact Master Equations

2007-08-04

arxiv.org/abs/0708.0644v1

Phys. Rev. B 77, 045319 (2008)

Physics

Condensed Matter

Strongly Correlated Electrons

14 pages, no figures

Scientific paper

10.1103/PhysRevB.77.045319

We consider a scenario where interacting electrons confined in quantum dots (QDs) are either too close to be resolved, or we do not wish to apply measurements that resolve them. Then the physical observable is an electron spin only (one cannot unambiguously ascribe a spin to a QD) and the system state is fully described by the spin-density matrix. Accounting for the spatial degrees of freedom, we examine to what extent a Hamiltonian description of the spin-only degrees of freedom is valid. We show that as long as there is no coupling between singlet and triplet states this is indeed the case, but when there is such a coupling there are open systems effects, i.e., the dynamics is non-unitary even without interaction with a true bath. Our primary focus is an investigation of non-unitary effects, based on exact master equations we derive for the spin-density matrix in the Lindblad and time-convolutionless (TCL) forms, and the implications for quantum computation. In particular, we demonstrate that the Heisenberg interaction does not affect the unitary part (apart from a Lamb shift) but does affect the non-unitary contributions to time evolution of the spin-density matrix. In a sequel paper we present a detailed analysis of an example system of two quantum dots, including spin-orbit effects.

Affiliated with

Also associated with

No associations

Rating

The Spin Density Matrix I: General Theory and Exact Master Equations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The Spin Density Matrix I: General Theory and Exact Master Equations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Spin Density Matrix I: General Theory and Exact Master Equations will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-500356