Measurements have been made of the distribution in time of arrival of photons produced in a low-pressure ${\mathrm{Hg}}^{198}$ discharge. Sufficient calibration was done so that the measurements could be directly compared with the predictions of a calculation of ${G}^{(2)}({x}_{1},{x}_{2},{x}_{2},{x}_{1})$ , the second-order coherence function. Correlations were observed in a mixture of light from two independent sources and between orthogonally polarized components of a beam initially in a pure polarization state.Measurements have been made of the distribution in time of arrival of photons produced in a low-pressure ${\mathrm{Hg}}^{198}$ discharge. Sufficient calibration was done so that the measurements could be directly compared with the predictions of a calculation of ${G}^{(2)}({x}_{1},{x}_{2},{x}_{2},{x}_{1})$, the second-order coherence function. Correlations were observed in a mixture of light from two independent sources and between orthogonally polarized components of a beam initially in a pure polarization state.

Physical ReviewNov 1, 196879 citations

Correlation between Photons in two Coherent Beams of Light

Robert Hanbury Brown, R. Q. Twiss

NatureJan 1, 19562,571 citations

Ultrashort coherence times in partially polarized stationary optical beams measured by two-photon absorption

Andriy Shevchenko, M. Roussey, Ari T. Friberg +1 more

We measure the recently introduced electromagnetic temporal degree of coherence of a stationary, partially polarized, classical optical beam. Instead of recording the visibility of intensity fringes, the spectrum, or the polarization characteristics, we introduce a novel technique based on two-photon absorption. Using a Michelson interferometer equipped with polarizers and a specific GaAs photocount tube, we obtain the two fundamental quantities pertaining to the fluctuations of light: the degree of coherence and the degree of polarization. We also show that the electromagnetic intensity-correlation measurements with two-photon absorption require that the polarization dynamics, i.e., the time evolution of the instantaneous polarization state, is properly taken into account. We apply the technique to unpolarized and polarized sources of amplified spontaneous emission (Gaussian statistics) and to a superposition of two independent, narrow-band laser beams of different mid frequencies (non-Gaussian statistics). For these two sources femtosecond-range coherence times are found that are in good agreement with the traditional spectral measurements. Although previously employed for laser pulses, two-photon absorption provides a new physical principle to study electromagnetic coherence phenomena in classical and quantum continuous-wave light at extremely short time scales.We measure the recently introduced electromagnetic temporal degree of coherence of a stationary, partially polarized, classical optical beam. Instead of recording the visibility of intensity fringes, the spectrum, or the polarization characteristics, we introduce a novel technique based on two-photon absorption. Using a Michelson interferometer equipped with polarizers and a specific GaAs photocount tube, we obtain the two fundamental quantities pertaining to the fluctuations of light: the degree of coherence and the degree of polarization. We also show that the electromagnetic intensity-correlation measurements with two-photon absorption require that the polarization dynamics, i.e., the time evolution of the instantaneous polarization state, is properly taken into account. We apply the technique to unpolarized and polarized sources of amplified spontaneous emission (Gaussian statistics) and to a superposition of two independent, narrow-band laser beams of different mid frequencies (non-Gaussian statistics). For these two sources femtosecond-range coherence times are found that are in good agreement with the traditional spectral measurements. Although previously employed for laser pulses, two-photon absorption provides a new physical principle to study electromagnetic coherence phenomena in classical and quantum continuous-wave light at extremely short time scales.

Optics ExpressNov 20, 201518 citations

Correlation between Photons in Two Coherent Beams of Light

R. Hanbury-Brown, R. Q. Twiss

Elsevier eBooksJan 1, 19835 citations

Partial polarization by quantum distinguishability

Mayukh Lahiri, Armin Hochrainer, Radek Łapkiewicz +2 more

We establish that a connection exists between wave-particle duality of photons and partial polarization of a light beam. We perform a two-path lowest-order (single photon) interference experiment and demonstrate both theoretically and experimentally that the degree of polarization of the light beam emerging from an output of the interferometer depends on path distinguishability. In our experiment, we are able to change the quantum state of the emerging photon from a pure state to a fully mixed state without any direct interaction with the photon. Although most lowest-order interference experiments can be explained by classical theory, our experiment has no genuine classical analog. Our results show that a case exists where the cause of partial polarization is beyond the scope of classical theory.We establish that a connection exists between wave-particle duality of photons and partial polarization of a light beam. We perform a two-path lowest-order (single photon) interference experiment and demonstrate both theoretically and experimentally that the degree of polarization of the light beam emerging from an output of the interferometer depends on path distinguishability. In our experiment, we are able to change the quantum state of the emerging photon from a pure state to a fully mixed state without any direct interaction with the photon. Although most lowest-order interference experiments can be explained by classical theory, our experiment has no genuine classical analog. Our results show that a case exists where the cause of partial polarization is beyond the scope of classical theory.

arXiv:1510.04192Physical Review AMar 16, 201727 citations

Correlation between photons in two coherent beams of light

Robert Hanbury Brown, R. Q. Twiss

Journal of Astrophysics and AstronomyMar 1, 199483 citations

Measurements have been made of the distribution in time of arrival of photons produced in a low-pressure

{\mathrm{Hg}}^{198}

discharge. Sufficient calibration was done so that the measurements could be directly compared with the predictions of a calculation of

{G}^{(2)}({x}_{1},{x}_{2},{x}_{2},{x}_{1})

, the second-order coherence function. Correlations were observed in a mixture of light from two independent sources and between orthogonally polarized components of a beam initially in a pure polarization state.