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Acta Sinica Quantum Optica

The Generation and Detection of Single-photon-state

Gao Jiangruiptics

Published Jan 1, 2004• 0 citations
OpenAlex

Abstract

Based on SPDC (Spontaneous Parametric Down-Conersion) the experiment of single-photon-state generation is completed in which a fs pulse laser is used to pump a type I noncollinear phase match BBO crystal and 1489 single-photon-states per second are get.

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Spectrum distribution of spontaneous parametric down-conversion is discussed in type-Ⅱ phase matching process with a Femto-second pulse laser pump.The spectrum distribution of signal and idle beams are different from each other and the differences vary with the width of Femta second pulse laser pump.We have also measured the spectrum distribution of type-Ⅱ phase matching BBO crystal's spontaneous parametric down-conversion beams.The results coincide with theorctical analysis.They are useful when measuring the light non-classical property with Femto-second pulse balance homodyne detecting system.
Summary form only given. Entangled photons are the workhorse of quantum information technology and cryptography. So far, the emphasis has been on entanglement of the polarization state (for type II down conversion), or of the wave vectors of the degenerate signal and idler pair (for type I down conversion). A subject of current interest is entanglement in the spatial domain, i.e. nontrivial, spatially extended, correlation between signal and idler. A prime example of this being the discussion regarding the conservation and entanglement of orbital angular momentum in spontaneous parametric down conversion. We report our very first measurements of the signal-idler correlation in type I down conversion, employing a frequency-doubled femtosecond Ti:sapphire laser as our source of pump photons, and a fourth generation intensified CCD as our "multi-element single-photon detector" With pump pulses at /spl lambda/ = 400 nm of approximately 2 nJ energy and 250 fs duration directed at a 0.5 mm long BBO crystal we detect roughly one pair in every four frames.
Quantum states of light, such as single photons, pairs of entangled photons, and squeezed light are a key resource for photonic quantum technologies. All these states can be obtained via the nonlinear optical effect of spontaneous parametric down-conversion (SPDC). In SPDC, a higher-energy photon of a coherent beam (pump) splits in two lower-energy daughter photons, called signal and idler. The photons of such a pair can be entangled in polarization, time/frequency, and position/momentum. Efficient generation of photon pairs requires a high second-order susceptibilityχ(2)\chi^{(2)}χ(2)of the material where it occurs, and the phase matching between the pump and the down-converted photons.