Fidelity for states of two \(\mathrm{spin-}\frac{1}{2}\) particles in moving frames. (English) Zbl 1171.81342

Nasr Esfahani, B.; Ahmadi, F.; Ahmadi, M.

Int. J. Theor. Phys. 48, No. 7, 1957-1964 (2009).

Summary: Fidelity for the spin part of states of two spin-\(\frac{1}{2}\) particles is investigated from the viewpoint of moving observers. Using a numerical approach, the behavior of the fidelity in terms of the boost parameter is described for different amounts of spin entanglement and momentum entanglement. It is shown that for the spin entangled states the fidelity decreases less than that of the case of spin product states and there are special cases for which the fidelity remains perfect regardless of moving observers’ velocity. Generally, in the limit of boosts with speeds close to the speed of light, the fidelity saturates, i.e., it reaches to a constant value that depends on the amount of momentum entanglement and the width of the momentum distribution function.

MSC:

81P68	Quantum computation
70H40	Relativistic dynamics for problems in Hamiltonian and Lagrangian mechanics
83A05	Special relativity
94A40	Channel models (including quantum) in information and communication theory

Keywords:

two-particle states; Wigner rotation; reduced density matrix; fidelity

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