RT Journal Article T1 Violation of Cauchy-Schwarz inequalities by spontaneous Hawking radiation in resonant boson structures A1 Muñoz de Nova, Juan Ramón A1 Sols Lucía, Fernando A1 Zapata, I. AB The violation of a classical Cauchy-Schwarz (CS) inequality is identified as an unequivocal signature of spontaneous Hawking radiation in sonic black holes. This violation can be particularly large near the peaks in the radiation spectrum emitted from a resonant boson structure forming a sonic horizon. As a function of the frequency-dependent Hawking radiation intensity, we analyze the degree of CS violation and the maximum violation temperature for a double barrier structure separating two regions of subsonic and supersonic condensate flow. We also consider the case where the resonant sonic horizon is produced by a space-dependent contact interaction. In some cases, CS violation can be observed by direct atom counting in a time-of-flight experiment. We show that near the conventional zero-frequency peak, the decisive CS violation cannot occur. PB American Physical Society SN 1050-2947 YR 2014 FD 2014-04-07 LK https://hdl.handle.net/20.500.14352/33621 UL https://hdl.handle.net/20.500.14352/33621 LA eng NO [1] S. W. Hawking, Nature (London) 248, 30 (1974); ,Commun. Math. Phys. 43, 199 (1975).[2] W. G. Unruh, Phys. Rev. D 14, 870 (1976).[3] W. G. Unruh, Phys. Rev. Lett. 46, 1351 (1981).[4] U. Leonhardt, T. Kiss, and P. O¨ hberg, J. Opt. B 5, S42 (2003).[5] U. Leonhardt, T. Kiss, and P. O¨ hberg, Phys. Rev. A 67, 033602 (2003).[6] R. Balbinot,A. Fabbri, S. Fagnocchi, A. Recati, and I. Carusotto, Phys. Rev. A 78, 021603 (2008).[7] I. Carusotto, S. Fagnocchi, A. Recati, R. Balbinot, and A. Fabri, New J. Phys. 10, 103001 (2008).[8] J. Macher and R. Parentani, Phys. Rev. A 80, 043601 (2009).[9] S. Finazzi and R. Parentani, New J. Phys. 12, 095015 (2010).[10] A. Coutant and R. Parentani, Phys. Rev. D 81, 084042 (2010).[11] O. Lahav, A. Itah, A. Blumkin, C. Gordon, S. Rinott, A. Zayats, and J. Steinhauer, Phys. Rev. Lett. 105, 240401 (2010).[12] I. Zapata, M. Albert, R. Parentani, and F. Sols, New J. Phys. 13, 063048 (2011).[13] P. É. Larré, A. Recati, I. Carusotto, and N. Pavloff, Phys. Rev. A 85, 013621 (2012).[14] N. D. Birrell and P. C. W. Davies, Quantum Fields in Curved Space (Cambridge University Press, Cambridge, 1982).[15] R. Loudon, The Quantum Theory of Light, 3rd ed. (Oxford University Press, New York, 2000).[16] D.F.Walls andG. J.Milburn, Quantum Optics, 2nd ed. (Springer Verlag, Berlin, 2008).[17] A. Recati, N. Pavloff, and I. Carusotto, Phys. Rev. A 80, 043603 (2009).[18] R. Schützhold, Phys. Rev. Lett. 97, 190405 (2006).[19] E. Rubino, J. McLenaghan, S. C. Kehr, F. Belgiorno, D. Townsend, S. Rohr, C. E. Kuklewicz, U. Leonhardt, F. König, and D. Faccio, Phys. Rev. Lett. 108, 253901 (2012).[20] D. Campo and R. Parentani, Phys. Rev. D 74, 025001 (2006).[21] E. Martín-Martínez, L. J. Garay, and J. Le´on, Phys. Rev. D 82, 064028 (2010).[22] N. Friis and I. Fuentes, J. Mod. Opt. 60, 22 (2013).[23] B. Horstmann, B. Reznik, S. Fagnocchi, and J. I. Cirac, Phys. Rev. Lett. 104, 250403 (2010).[24] B. Horstmann, R. Schützhold, B. Reznik, S. Fagnocchi, and J. I. Cirac, New J. Phys. 13, 045008 (2011).[25] S. Finazzi and I. Carusotto, arXiv:1309.3414.[26] K. V. Kheruntsyan, J.-C. Jaskula, P. Deuar, M. Bonneau, G. B. Partridge, J. Ruaudel, R. Lopes, D. Boiron, and C. I.Westbrook, Phys. Rev. Lett. 108, 260401 (2012).[27] Unless otherwise stated, we are not showing trivial Dirac-delta factors which ensure equal frequency to all phonons that participate in any correlation function.[28] Note that, because of the condensate flow, in general Sij ≠Sji .[29] I. Zapata and F. Sols, Phys. Rev. Lett. 102, 180405 (2009).[30] Note that the second type of quantum thermal average is nonzero only if i has a positive normalization and j a negative one, or vice versa.[31] V. I. Arnold, Ordinary Differential Equations (Springer Verlag, Berlin, 1992).[32] D. Kaltchev and A. J. Dragt, Physica D 242, 1 (2013).[33] Note that pd_2(ω) > 0 is always verified for ω < ωmax provided that k_(d2−out)(ω_max) < q_d . NO © 2014 American Physical Society.We thank D. Guery-Odelin, R. Parentani, and C.Westbrook for valuable discussions. Support from MINECO (Spain) through grant FIS2010-21372 and from Comunidad de Madrid through grant MICROSERES-CM (S2009/TIC-1476) is also acknowledged. NO Comunidad de Madrid NO Ministerio de Economía y Competitividad (MINECO) DS Docta Complutense RD 3 may 2024