Interference of Temporally Distinguishable Photons Using Frequency-Resolved Detection

Abstract

We demonstrate quantum interference of three photons that are distinguishable in time, by resolving them in the conjugate parameter, frequency. We show that the multiphoton interference pattern in our setup can be manipulated by tuning the relative delays between the photons, without the need for reconfiguring the optical network. Furthermore, we observe that the symmetries of our optical network and the spectral amplitude of the input photons are manifested in the interference pattern. We also demonstrate time-reversed Hong-Ou-Mandellike interference in the spectral correlations using time-bin entangled photon pairs. By adding a time-varying dispersion using a phase modulator, our setup can be used to realize dynamically reconfigurable and scalable boson sampling in the time domain as well as frequency-resolved multiboson correlation sampling.The nonclassical interference of two or more photons in an optical network is the fundamental phenomenon enabling many algorithms used in linear optics quantum computing [1][2][3][4], quantum communications [5][6][7], metrology [8,9] and boson sampling [10][11][12]. Quantum interference, such as, Hong-Ou-Mandel (HOM) and Shih-Alley interference [13,14], usually requires photons that are identical in their temporal and spectral degrees of freedom. Any distinguishability in the photons at the detectors leads to a reduction in the interference. The difficulty in experimentally generating identical photons has prompted strong interest in developing real world optical networks enabling the interference of nonidentical photons [15,16]. Recently, it was shown that nonclassical interference can be observed between photons completely distinguishable in time or frequency by exploiting correlation measurements in the corresponding conjugate parameter [17][18][19][20][21]. Remarkably, the interference can occur for any values of the input frequencies (or times) as long as the detector resolution in the conjugate parameter is sufficient to make the detectors 'blind' to the spectral (or temporal) distinguishability of the photons. Furthermore, the temporal or spectral distinguishability can actually be used as a resource, for example, to reveal spectral properties of the input photons and the symmetries of the optical network [19,20].Many experiments have demonstrated interference of two photons that are distinguishable in frequency or time by resolving them in the conjugate parameter [17,18,22,23]. Scaling these spectrally or temporally resolved interference phenomena to a larger number of photons can enable, for example, multiboson correlation sampling experiments where sampling over temporal or spectral modes, in addition to spatial modes, can relax the requirements on generating identical photons and could demonstrate quantum supremacy [24][25][26][27]. Indeed, time-resolved interference of three photons with different frequencies was demonstrated very recently where the temporal correlations between detected photons were manipulated using a spatial network of beam splitters [21]. In...

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