G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, “Interference structure of two-photon amplitude revealed by dispersion spreading,” Phys. Rev. A 75, 015801 (2007).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, M. Gramegna, and L. A. Krivitsky, “Dispersion spreading of Biphotons in Optical Fibers and Two-Photon Interference,” Phys. Rev. Lett. 96, 143601 (2006).

[Crossref]
[PubMed]

M. Genovese, “Research on hidden variable theories: A review of recent progresses,” Phys. Rep. 413, 319–396 (2005).

[Crossref]

J. Rarity, J. Fulconis, J. Duligall, W. Wadsworth, and P. Russell, “Photonic crystal fiber source of correlated photon pairs,” Opt. Express 13, 534–544 (2005).

[Crossref]
[PubMed]

H. Takesue and K. Inoue, “Generation of polarization-entangled photon pairs and violation of Bell’s inequality using spontaneous four-wave mixing in a fiber loop,” Phys. Rev. A 70, 031802(R) (2004).

[Crossref]

K. Banaszek, A. Dragan, W. Wasilewski, and C. Radzewicz, “Experimental demonstration of entanglement-enhanced classical communication over a quantum channel with correlated noise,” Phys. Rev. Lett. 92, 257901 (2004).

[Crossref]
[PubMed]

M. W. Mitchell, C. W. Ellenor, S. Schneider, and A. M. Steinberg, “Diagnosis, Prescription, and Prognosis of a Bell-State Filter by Quantum Process Tomography,” Phys. Rev. Lett. 91, 120402 (2003).

[Crossref]
[PubMed]

A. V. Burlakov, S. P. Kulik, G. O. Rytikov, and M. V. Chekhova, “Biphoton light generation in polarization-frequency bell states,” JETP 95, 639–644 (2002).

[Crossref]

Y. H. Kim, S. P. Kulik, and Y. H. Shih, “Bell-state preparation using pulsed nondegenerate two-photon entanglement,” Phys. Rev. A 63, 060301(R) (2001).

[Crossref]

L. J. Wang, C. K. Hong, and S. R. Friberg, “Generation of correlated photons via four-wave mixing in optical fibres,” J. Opt. B: Quantum and Semiclass. Opt. 3, 346–352 (2001).

[Crossref]

J. E. Sharping, M. Fiorentino, and P. Kumar, “Observation of twin-beam-type quantum correlation in optical fiber,” Opt. Lett. 26, 367369 (2001).

[Crossref]

G. Brida, M. Genovese, C. Novero, and E. Predazzi, “New experimental test of Bell inequalities by the use of a non-maximally entangled photon state,” Phys. Lett. A 268, 12–16 (2000).

[Crossref]

P. G. Kwiat, A. J. Berglund, J. B. Altepeter, and A. G. White, “Experimental verification of decoherence-free subspaces,” Science 290, 498–501 (2000).

[Crossref]
[PubMed]

P. G. Kwiat, E. Waks, A. G. White, I. Appelbaum, and P. G. Eberhard, “Ultrabright source of polarization-entangled photons,” Phys. Rev. A 60, R773–R776 (1999).

[Crossref]

D. Boschi, S. Branca, F. De Martini, L. Hardy, and S. Popescu, “Experimental realization of teleporting an unknown pure quantum state via dual classical and Einstein-Podolsky-Rosen channels,” Phys. Rev. Lett. 80, 1121–1125 (1998).

[Crossref]

D. Bouwmeester, J.-W. Pan, K. Mattle, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum teleportation,” Nature 390, 575–578 (1997).

[Crossref]

S. Braunstein and A. Mann, “Measurement of the Bell operator and quantum teleportation,” Phys. Rev. A 51, R1727–R1730 (1995).

[Crossref]
[PubMed]

P. G. Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. H. Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).

[Crossref]
[PubMed]

V. P. Karassiov and A. V. Masalov, “Nonpolarized states of light in quantum optics,” Opt. Spectrosc. 74, 928–936 (1993).

P. G. Kwiat, A. J. Berglund, J. B. Altepeter, and A. G. White, “Experimental verification of decoherence-free subspaces,” Science 290, 498–501 (2000).

[Crossref]
[PubMed]

P. G. Kwiat, E. Waks, A. G. White, I. Appelbaum, and P. G. Eberhard, “Ultrabright source of polarization-entangled photons,” Phys. Rev. A 60, R773–R776 (1999).

[Crossref]

K. Banaszek, A. Dragan, W. Wasilewski, and C. Radzewicz, “Experimental demonstration of entanglement-enhanced classical communication over a quantum channel with correlated noise,” Phys. Rev. Lett. 92, 257901 (2004).

[Crossref]
[PubMed]

P. G. Kwiat, A. J. Berglund, J. B. Altepeter, and A. G. White, “Experimental verification of decoherence-free subspaces,” Science 290, 498–501 (2000).

[Crossref]
[PubMed]

D. Boschi, S. Branca, F. De Martini, L. Hardy, and S. Popescu, “Experimental realization of teleporting an unknown pure quantum state via dual classical and Einstein-Podolsky-Rosen channels,” Phys. Rev. Lett. 80, 1121–1125 (1998).

[Crossref]

D. Bouwmeester, J.-W. Pan, K. Mattle, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum teleportation,” Nature 390, 575–578 (1997).

[Crossref]

D. Boschi, S. Branca, F. De Martini, L. Hardy, and S. Popescu, “Experimental realization of teleporting an unknown pure quantum state via dual classical and Einstein-Podolsky-Rosen channels,” Phys. Rev. Lett. 80, 1121–1125 (1998).

[Crossref]

S. Braunstein and A. Mann, “Measurement of the Bell operator and quantum teleportation,” Phys. Rev. A 51, R1727–R1730 (1995).

[Crossref]
[PubMed]

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, “Interference structure of two-photon amplitude revealed by dispersion spreading,” Phys. Rev. A 75, 015801 (2007).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, M. Gramegna, and L. A. Krivitsky, “Dispersion spreading of Biphotons in Optical Fibers and Two-Photon Interference,” Phys. Rev. Lett. 96, 143601 (2006).

[Crossref]
[PubMed]

G. Brida, M. Genovese, C. Novero, and E. Predazzi, “New experimental test of Bell inequalities by the use of a non-maximally entangled photon state,” Phys. Lett. A 268, 12–16 (2000).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, submitted a manuscript called “Bell states generation within the SPDC phase-matching bandwidth.”

A. V. Burlakov, S. P. Kulik, G. O. Rytikov, and M. V. Chekhova, “Biphoton light generation in polarization-frequency bell states,” JETP 95, 639–644 (2002).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, “Interference structure of two-photon amplitude revealed by dispersion spreading,” Phys. Rev. A 75, 015801 (2007).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, M. Gramegna, and L. A. Krivitsky, “Dispersion spreading of Biphotons in Optical Fibers and Two-Photon Interference,” Phys. Rev. Lett. 96, 143601 (2006).

[Crossref]
[PubMed]

A. V. Burlakov, S. P. Kulik, G. O. Rytikov, and M. V. Chekhova, “Biphoton light generation in polarization-frequency bell states,” JETP 95, 639–644 (2002).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, submitted a manuscript called “Bell states generation within the SPDC phase-matching bandwidth.”

D. Boschi, S. Branca, F. De Martini, L. Hardy, and S. Popescu, “Experimental realization of teleporting an unknown pure quantum state via dual classical and Einstein-Podolsky-Rosen channels,” Phys. Rev. Lett. 80, 1121–1125 (1998).

[Crossref]

K. Banaszek, A. Dragan, W. Wasilewski, and C. Radzewicz, “Experimental demonstration of entanglement-enhanced classical communication over a quantum channel with correlated noise,” Phys. Rev. Lett. 92, 257901 (2004).

[Crossref]
[PubMed]

P. G. Kwiat, E. Waks, A. G. White, I. Appelbaum, and P. G. Eberhard, “Ultrabright source of polarization-entangled photons,” Phys. Rev. A 60, R773–R776 (1999).

[Crossref]

D. Bouwmeester, J.-W. Pan, K. Mattle, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum teleportation,” Nature 390, 575–578 (1997).

[Crossref]

M. W. Mitchell, C. W. Ellenor, S. Schneider, and A. M. Steinberg, “Diagnosis, Prescription, and Prognosis of a Bell-State Filter by Quantum Process Tomography,” Phys. Rev. Lett. 91, 120402 (2003).

[Crossref]
[PubMed]

J. E. Sharping, M. Fiorentino, and P. Kumar, “Observation of twin-beam-type quantum correlation in optical fiber,” Opt. Lett. 26, 367369 (2001).

[Crossref]

L. J. Wang, C. K. Hong, and S. R. Friberg, “Generation of correlated photons via four-wave mixing in optical fibres,” J. Opt. B: Quantum and Semiclass. Opt. 3, 346–352 (2001).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, “Interference structure of two-photon amplitude revealed by dispersion spreading,” Phys. Rev. A 75, 015801 (2007).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, M. Gramegna, and L. A. Krivitsky, “Dispersion spreading of Biphotons in Optical Fibers and Two-Photon Interference,” Phys. Rev. Lett. 96, 143601 (2006).

[Crossref]
[PubMed]

M. Genovese, “Research on hidden variable theories: A review of recent progresses,” Phys. Rep. 413, 319–396 (2005).

[Crossref]

G. Brida, M. Genovese, C. Novero, and E. Predazzi, “New experimental test of Bell inequalities by the use of a non-maximally entangled photon state,” Phys. Lett. A 268, 12–16 (2000).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, submitted a manuscript called “Bell states generation within the SPDC phase-matching bandwidth.”

G. Brida, M. V. Chekhova, M. Genovese, M. Gramegna, and L. A. Krivitsky, “Dispersion spreading of Biphotons in Optical Fibers and Two-Photon Interference,” Phys. Rev. Lett. 96, 143601 (2006).

[Crossref]
[PubMed]

D. Boschi, S. Branca, F. De Martini, L. Hardy, and S. Popescu, “Experimental realization of teleporting an unknown pure quantum state via dual classical and Einstein-Podolsky-Rosen channels,” Phys. Rev. Lett. 80, 1121–1125 (1998).

[Crossref]

L. J. Wang, C. K. Hong, and S. R. Friberg, “Generation of correlated photons via four-wave mixing in optical fibres,” J. Opt. B: Quantum and Semiclass. Opt. 3, 346–352 (2001).

[Crossref]

H. Takesue and K. Inoue, “Generation of polarization-entangled photon pairs and violation of Bell’s inequality using spontaneous four-wave mixing in a fiber loop,” Phys. Rev. A 70, 031802(R) (2004).

[Crossref]

V. P. Karassiov and A. V. Masalov, “Nonpolarized states of light in quantum optics,” Opt. Spectrosc. 74, 928–936 (1993).

Y. H. Kim, S. P. Kulik, and Y. H. Shih, “Bell-state preparation using pulsed nondegenerate two-photon entanglement,” Phys. Rev. A 63, 060301(R) (2001).

[Crossref]

D. N. Klyshko, Photons and Nonlinear Optics (Gordon and Breach, New York, 1988).

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, “Interference structure of two-photon amplitude revealed by dispersion spreading,” Phys. Rev. A 75, 015801 (2007).

[Crossref]

G. Brida, M. V. Chekhova, M. Genovese, M. Gramegna, and L. A. Krivitsky, “Dispersion spreading of Biphotons in Optical Fibers and Two-Photon Interference,” Phys. Rev. Lett. 96, 143601 (2006).

[Crossref]
[PubMed]

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, submitted a manuscript called “Bell states generation within the SPDC phase-matching bandwidth.”

A. V. Burlakov, S. P. Kulik, G. O. Rytikov, and M. V. Chekhova, “Biphoton light generation in polarization-frequency bell states,” JETP 95, 639–644 (2002).

[Crossref]

Y. H. Kim, S. P. Kulik, and Y. H. Shih, “Bell-state preparation using pulsed nondegenerate two-photon entanglement,” Phys. Rev. A 63, 060301(R) (2001).

[Crossref]

J. E. Sharping, M. Fiorentino, and P. Kumar, “Observation of twin-beam-type quantum correlation in optical fiber,” Opt. Lett. 26, 367369 (2001).

[Crossref]

P. G. Kwiat, A. J. Berglund, J. B. Altepeter, and A. G. White, “Experimental verification of decoherence-free subspaces,” Science 290, 498–501 (2000).

[Crossref]
[PubMed]

P. G. Kwiat, E. Waks, A. G. White, I. Appelbaum, and P. G. Eberhard, “Ultrabright source of polarization-entangled photons,” Phys. Rev. A 60, R773–R776 (1999).

[Crossref]

P. G. Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. H. Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).

[Crossref]
[PubMed]

S. Braunstein and A. Mann, “Measurement of the Bell operator and quantum teleportation,” Phys. Rev. A 51, R1727–R1730 (1995).

[Crossref]
[PubMed]

V. P. Karassiov and A. V. Masalov, “Nonpolarized states of light in quantum optics,” Opt. Spectrosc. 74, 928–936 (1993).

D. Bouwmeester, J.-W. Pan, K. Mattle, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum teleportation,” Nature 390, 575–578 (1997).

[Crossref]

P. G. Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. H. Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).

[Crossref]
[PubMed]

M. W. Mitchell, C. W. Ellenor, S. Schneider, and A. M. Steinberg, “Diagnosis, Prescription, and Prognosis of a Bell-State Filter by Quantum Process Tomography,” Phys. Rev. Lett. 91, 120402 (2003).

[Crossref]
[PubMed]

G. Brida, M. Genovese, C. Novero, and E. Predazzi, “New experimental test of Bell inequalities by the use of a non-maximally entangled photon state,” Phys. Lett. A 268, 12–16 (2000).

[Crossref]

D. Bouwmeester, J.-W. Pan, K. Mattle, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum teleportation,” Nature 390, 575–578 (1997).

[Crossref]

D. Boschi, S. Branca, F. De Martini, L. Hardy, and S. Popescu, “Experimental realization of teleporting an unknown pure quantum state via dual classical and Einstein-Podolsky-Rosen channels,” Phys. Rev. Lett. 80, 1121–1125 (1998).

[Crossref]

G. Brida, M. Genovese, C. Novero, and E. Predazzi, “New experimental test of Bell inequalities by the use of a non-maximally entangled photon state,” Phys. Lett. A 268, 12–16 (2000).

[Crossref]

K. Banaszek, A. Dragan, W. Wasilewski, and C. Radzewicz, “Experimental demonstration of entanglement-enhanced classical communication over a quantum channel with correlated noise,” Phys. Rev. Lett. 92, 257901 (2004).

[Crossref]
[PubMed]

A. V. Burlakov, S. P. Kulik, G. O. Rytikov, and M. V. Chekhova, “Biphoton light generation in polarization-frequency bell states,” JETP 95, 639–644 (2002).

[Crossref]

M. W. Mitchell, C. W. Ellenor, S. Schneider, and A. M. Steinberg, “Diagnosis, Prescription, and Prognosis of a Bell-State Filter by Quantum Process Tomography,” Phys. Rev. Lett. 91, 120402 (2003).

[Crossref]
[PubMed]

P. G. Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. H. Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).

[Crossref]
[PubMed]

J. E. Sharping, M. Fiorentino, and P. Kumar, “Observation of twin-beam-type quantum correlation in optical fiber,” Opt. Lett. 26, 367369 (2001).

[Crossref]

Y. H. Kim, S. P. Kulik, and Y. H. Shih, “Bell-state preparation using pulsed nondegenerate two-photon entanglement,” Phys. Rev. A 63, 060301(R) (2001).

[Crossref]

P. G. Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. H. Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).

[Crossref]
[PubMed]

M. W. Mitchell, C. W. Ellenor, S. Schneider, and A. M. Steinberg, “Diagnosis, Prescription, and Prognosis of a Bell-State Filter by Quantum Process Tomography,” Phys. Rev. Lett. 91, 120402 (2003).

[Crossref]
[PubMed]

H. Takesue and K. Inoue, “Generation of polarization-entangled photon pairs and violation of Bell’s inequality using spontaneous four-wave mixing in a fiber loop,” Phys. Rev. A 70, 031802(R) (2004).

[Crossref]

P. G. Kwiat, E. Waks, A. G. White, I. Appelbaum, and P. G. Eberhard, “Ultrabright source of polarization-entangled photons,” Phys. Rev. A 60, R773–R776 (1999).

[Crossref]

L. J. Wang, C. K. Hong, and S. R. Friberg, “Generation of correlated photons via four-wave mixing in optical fibres,” J. Opt. B: Quantum and Semiclass. Opt. 3, 346–352 (2001).

[Crossref]

K. Banaszek, A. Dragan, W. Wasilewski, and C. Radzewicz, “Experimental demonstration of entanglement-enhanced classical communication over a quantum channel with correlated noise,” Phys. Rev. Lett. 92, 257901 (2004).

[Crossref]
[PubMed]

D. Bouwmeester, J.-W. Pan, K. Mattle, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum teleportation,” Nature 390, 575–578 (1997).

[Crossref]

P. G. Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. H. Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).

[Crossref]
[PubMed]

P. G. Kwiat, A. J. Berglund, J. B. Altepeter, and A. G. White, “Experimental verification of decoherence-free subspaces,” Science 290, 498–501 (2000).

[Crossref]
[PubMed]

P. G. Kwiat, E. Waks, A. G. White, I. Appelbaum, and P. G. Eberhard, “Ultrabright source of polarization-entangled photons,” Phys. Rev. A 60, R773–R776 (1999).

[Crossref]

In this regime higher-order contributions are negligible as shown both from theoretical and experimental results, e.g. G. Zambra et al., Phys. Rev. Lett.95, 063602 (2005).

[Crossref]
[PubMed]

D. Bouwmeester, J.-W. Pan, K. Mattle, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum teleportation,” Nature 390, 575–578 (1997).

[Crossref]

P. G. Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. H. Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).

[Crossref]
[PubMed]

L. J. Wang, C. K. Hong, and S. R. Friberg, “Generation of correlated photons via four-wave mixing in optical fibres,” J. Opt. B: Quantum and Semiclass. Opt. 3, 346–352 (2001).

[Crossref]

A. V. Burlakov, S. P. Kulik, G. O. Rytikov, and M. V. Chekhova, “Biphoton light generation in polarization-frequency bell states,” JETP 95, 639–644 (2002).

[Crossref]

D. Bouwmeester, J.-W. Pan, K. Mattle, M. Eibl, H. Weinfurter, and A. Zeilinger, “Experimental quantum teleportation,” Nature 390, 575–578 (1997).

[Crossref]

J. E. Sharping, M. Fiorentino, and P. Kumar, “Observation of twin-beam-type quantum correlation in optical fiber,” Opt. Lett. 26, 367369 (2001).

[Crossref]

V. P. Karassiov and A. V. Masalov, “Nonpolarized states of light in quantum optics,” Opt. Spectrosc. 74, 928–936 (1993).

G. Brida, M. Genovese, C. Novero, and E. Predazzi, “New experimental test of Bell inequalities by the use of a non-maximally entangled photon state,” Phys. Lett. A 268, 12–16 (2000).

[Crossref]

M. Genovese, “Research on hidden variable theories: A review of recent progresses,” Phys. Rep. 413, 319–396 (2005).

[Crossref]

Y. H. Kim, S. P. Kulik, and Y. H. Shih, “Bell-state preparation using pulsed nondegenerate two-photon entanglement,” Phys. Rev. A 63, 060301(R) (2001).

[Crossref]

H. Takesue and K. Inoue, “Generation of polarization-entangled photon pairs and violation of Bell’s inequality using spontaneous four-wave mixing in a fiber loop,” Phys. Rev. A 70, 031802(R) (2004).

[Crossref]

P. G. Kwiat, E. Waks, A. G. White, I. Appelbaum, and P. G. Eberhard, “Ultrabright source of polarization-entangled photons,” Phys. Rev. A 60, R773–R776 (1999).

[Crossref]

S. Braunstein and A. Mann, “Measurement of the Bell operator and quantum teleportation,” Phys. Rev. A 51, R1727–R1730 (1995).

[Crossref]
[PubMed]

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, “Interference structure of two-photon amplitude revealed by dispersion spreading,” Phys. Rev. A 75, 015801 (2007).

[Crossref]

D. Boschi, S. Branca, F. De Martini, L. Hardy, and S. Popescu, “Experimental realization of teleporting an unknown pure quantum state via dual classical and Einstein-Podolsky-Rosen channels,” Phys. Rev. Lett. 80, 1121–1125 (1998).

[Crossref]

K. Banaszek, A. Dragan, W. Wasilewski, and C. Radzewicz, “Experimental demonstration of entanglement-enhanced classical communication over a quantum channel with correlated noise,” Phys. Rev. Lett. 92, 257901 (2004).

[Crossref]
[PubMed]

G. Brida, M. V. Chekhova, M. Genovese, M. Gramegna, and L. A. Krivitsky, “Dispersion spreading of Biphotons in Optical Fibers and Two-Photon Interference,” Phys. Rev. Lett. 96, 143601 (2006).

[Crossref]
[PubMed]

M. W. Mitchell, C. W. Ellenor, S. Schneider, and A. M. Steinberg, “Diagnosis, Prescription, and Prognosis of a Bell-State Filter by Quantum Process Tomography,” Phys. Rev. Lett. 91, 120402 (2003).

[Crossref]
[PubMed]

P. G. Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, A. V. Sergienko, and Y. H. Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).

[Crossref]
[PubMed]

P. G. Kwiat, A. J. Berglund, J. B. Altepeter, and A. G. White, “Experimental verification of decoherence-free subspaces,” Science 290, 498–501 (2000).

[Crossref]
[PubMed]

Because in half of the cases both photons go to the same output, the state is produced with 50% probability.

In this regime higher-order contributions are negligible as shown both from theoretical and experimental results, e.g. G. Zambra et al., Phys. Rev. Lett.95, 063602 (2005).

[Crossref]
[PubMed]

G. Brida, M. V. Chekhova, M. Genovese, and L. A. Krivitsky, submitted a manuscript called “Bell states generation within the SPDC phase-matching bandwidth.”

D. N. Klyshko, Photons and Nonlinear Optics (Gordon and Breach, New York, 1988).