Continuous-variable phase estimation with unitary and random linear disturbance

Autor(es)

de Souza, Douglas Delgado ^{[1, 2]} ; Genoni, Marco G. ^[3] ; Kim, M. S. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP - Brazil

^[2] Univ London Imperial Coll Sci Technol & Med, QOLS, Blackett Lab, London SW7 2BW - England

^[3] UCL, Dept Phys & Astron, London WC1E 6BT - England

• Tipo de documento: Artigo Científico
• Fonte: Physical Review A; v. 90, n. 4 OCT 27 2014.
• Citações Web of Science: 4

Resumo

We address the problem of continuous-variable quantum phase estimation in the presence of linear disturbance at the Hamiltonian level by means of Gaussian probe states. In particular we discuss both unitary and random disturbance by considering the parameter which characterizes the unwanted linear term present in the Hamiltonian as fixed (unitary disturbance) or random with a given probability distribution (random disturbance). We derive the optimal input Gaussian states at fixed energy, maximizing the quantum Fisher information over the squeezing angle and the squeezing energy fraction, and we discuss the scaling of the quantum Fisher information in terms of the output number of photons, n(out). We observe that, in the case of unitary disturbance, the optimal state is a squeezed vacuum state and the quadratic scaling is conserved. As regards the random disturbance, we observe that the optimal squeezing fraction may not be equal to one and, for any nonzero value of the noise parameter, the quantum Fisher information scales linearly with the average number of photons. Finally, we discuss the performance of homodyne measurement by comparing the achievable precision with the ultimate limit imposed by the quantum Cramer-Rao bound. (AU)

• Processo FAPESP: 11/00220-5 - Informação Quântica com estados coerentes comprimidos
• Beneficiário: Douglas Delgado de Souza
• Modalidade de apoio: Bolsas no Brasil - Doutorado