Abstract
The indistinguishability of independent single photons is presented by decomposing the single photon pulse into the mixed state of different transform-limited pulses. The entanglement between single photons and outer environment or other photons induces the distribution of the center frequencies of those transform-limited pulses and makes photons distinguishable. Only the single photons with the same transform-limited form are indistinguishable. In details, the indistinguishability of single photons from the solid-state quantum emitter and spontaneous parametric down-conversion is examined with two-photon Hong-Ou-Mandel interferometer. Moreover, experimental methods to enhance the indistinguishability are discussed, where the usage of spectral filter is highlighted.
Highlights
Linear optical quantum computation1͔ is based on the interference between different photons2͔, in which the indistinguishability of photons is a fundamental and critical requirement
The indistinguishability of independent single photons is presented by decomposing the single photon pulse into the mixed state of different transform-limited pulses
The kernel is the indistinguishability of independent single photons
Summary
Linear optical quantum computation1͔ is based on the interference between different photons2͔, in which the indistinguishability of photons is a fundamental and critical requirement. The distinguishability of the single photons comes from the entanglement with extrinsic system, such as photons, phonons or outer environment. In SPDC, the property of entanglement can be achieved through the analysis of the phasematching condition22,29͔ It is more complicated in the solid-state quantum emitters. In the single quantum dot, the interaction with phonon results in short dephasing time and gives rises to a very broad spectrum of the photons30͔ This spectrum broadening will make photons distinguishable. When the extrinsic width is much larger than the intrinsic width, the single photons are totally distinguishable. We will examine the indistinguishability of single photons from solid quantum emitters and SPDC after a general description of the single photon state is given. Experimental methods to enhance the indistinguishability are presented, where the effect of spectral filter is highlighted
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