Phase variance of squeezed vacuum states
Bagán Capella, Emili ![Identificador ORCID](/img/uab/orcid.ico)
(Universitat Autònoma de Barcelona. Departament de Física)
Monras Blasi, Àlex (University of Leeds. The School of Physics and Astronomy)
Muñoz Tapia, Ramon ![Identificador ORCID](/img/uab/orcid.ico)
(Universitat Autònoma de Barcelona. Departament de Física)
American Physical Society
Data: |
2008 |
Resum: |
We consider the problem of estimating the phase of squeezed vacuum states within a Bayesian framework. We derive bounds on the average Holevo variance for an arbitrary number N of uncorrelated copies. We find that it scales with the mean photon number n, as dictated by the Heisenberg limit, i. e. , as n−2, only for N>4. For N 4 this fundamental scaling breaks down and it becomes n−N/2. Thus, a single squeezed vacuum state performs worse than a single coherent state with the same energy. We find the optimal splitting of a fixed given energy among various copies. We also compute the variance for repeated individual measurements (without classical communication or adaptivity) and find that the standard Heisenberg-limited scaling n−2 is recovered for large samples. |
Drets: |
Tots els drets reservats. ![](/img/licenses/InC.ico) |
Llengua: |
Anglès |
Document: |
Article ; recerca ; Versió publicada |
Publicat a: |
Physical review. A, Vol. 78, Issue 4 (October 2008) , p. 043829-1-043829-7, ISSN 1050-2947 |
DOI: 10.1103/PhysRevA.78.043829
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