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Highlights • Thermal effect of the biphotons generated from M TiO X O 4 is thoroughly investigated. • The thermal effect is the key to precisely control the quantum state. • The maximal spectral purity of biphotons is insensitive to temperature shift. • The HOM interference patterns are very sensitive to temperature shift. • The research results are useful for quantum interference and spectroscopy. Abstract We theoretically and numerically investigate the temperature-dependent properties of the biphotons generated from four isomorphs of periodically poled KTiOPO 4 (PPKTP): i.e., PPRTP, PPKTA, PPRTA and PPCTA. It is discovered that the first type of group-velocity-matched (GVM) wavelength is decreased by 6.4, 1.2, 8.9, 25.6 and 6.3 nm, while the phase-matched wavelength is decreased by 4.4, −0.4, −1.2, 29.1 and 59.5 nm for PPKTP, PPRTP, PPKTA, PPRTA and PPCTA, respectively, when the temperature is increased from 20 °C to 120 °C. Although the maximal spectral purity of the heralded single photons is not changed at different temperature, the Hong-Ou-Mandel (HOM) interference shows different patterns due to a shift of the joint spectral amplitude. These thermal effects are very important for precise control of the quantum state for the future applications in quantum information processing, for example, in quantum interference or spectroscopy. [ABSTRACT FROM AUTHOR]

A modified Hong–Ou–Mandel (HOM) interference reveals that the two-photon interference phenomenon can be explained only by the concept of a two-photon wave packet rather than a single-photon one. However, the temporal interferogram in the modified HOM interferometer becomes flat in some cases so that no useful information can be extracted from time-domain measurement. Here, we theoretically explore such temporal interferogram from the frequency domain and obtain the spectrally resolved interference with high visibility. The result represents a modulation of the joint spectral intensity along both the frequency sum and the frequency difference directions. This is quite different from the cases of the spectrally resolved HOM interference and N00N state interference where the modulations happened only in one direction. Moreover, we have shown that such modulations have a potential application in the generation and characterization of high-dimensional frequency entanglement. • Spectrally resolved interference with high visibility in the modified HOM interferometer can be obtained even if the temporal visibility is zero. • Joint spectral intensity can be modulated by the time delay along both the frequency sum and the frequency difference directions. • High-dimensional frequency entanglement can be generated by adjusting the time delay and can be characterized directly using the two-side dips appeared in temporal interferogram. • The research results could facilitate further development of spectrally resolved multi-photon interference and its applications in quantum information science. [ABSTRACT FROM AUTHOR]