Abstract
Cavity-enhanced Spontaneous parametric down-conversion (SPDC) is capable of efficient generation of single photons with suitable spectral properties for interfacing with the atoms. However, beside the remarkable progress of this technique, multi-mode longitudinal emission remains as major drawback. Here we demonstrate a bright source of single photons that overcomes this limitation by a novel mode-selection technique based on the introduction of an additional birefringent element to the cavity. This enables us to tune the double resonance condition independent of the phase matching, and thus to achieve single-mode operation without mode filters. Our source emits single-frequency-mode photons at 852 nm, which is compatible to the Cs D2 line, with a bandwidth of 10.9 MHz and a photon-pair generation rate exceeding 47 KHz at 10 mW of pump power, while maintaining a low $g^{\left(2\right)}(0) =$ 0.13. The efficiency of our source is further underlined by measuring a four-photon generation rate of 37 Hz at 20 mW of pump power. This brightness opens up a variety of new applications reaching from hybrid light-matter interactions to optical quantum information tasks based on long temporal coherence.
Highlights
INTRODUCTIONPhotons’ mobility, efficient detection, and ease of manipulation allows for observing many quantum phenomena and makes them a natural candidate for quantum information processing applications. the lack of photon-photon interactions raises the challenge to implement two-qubit gates. One promising strategy to overcome this is interfacing single photons with the strong optical nonlinearities provided by matter-based quantum systems. Such hybrid quantum systems, with the combined benefits of both photons and matter, can realize quantum devices such as twoqubit gates, quantum memories, quantum repeaters, and eventually a full-scale quantum network
Photons’ mobility, efficient detection, and ease of manipulation allows for observing many quantum phenomena1,2 and makes them a natural candidate for quantum information processing applications.3–7 the lack of photon-photon interactions raises the challenge to implement two-qubit gates.8 One promising strategy to overcome this is interfacing single photons with the strong optical nonlinearities provided by matter-based quantum systems.9–12 Such hybrid quantum systems, with the combined benefits of both photons and matter, can realize quantum devices such as twoqubit gates, quantum memories, quantum repeaters, and eventually a full-scale quantum network.13Spontaneous parametric down-conversion (SPDC) has been widely used to generate high-purity single photons14 at a broad range of frequencies at room temperature
Cavity-enhanced spontaneous parametric down-conversion is capable of efficient generation of single photons with suitable spectral properties for interfacing with the atoms
Summary
Photons’ mobility, efficient detection, and ease of manipulation allows for observing many quantum phenomena and makes them a natural candidate for quantum information processing applications. the lack of photon-photon interactions raises the challenge to implement two-qubit gates. One promising strategy to overcome this is interfacing single photons with the strong optical nonlinearities provided by matter-based quantum systems. Such hybrid quantum systems, with the combined benefits of both photons and matter, can realize quantum devices such as twoqubit gates, quantum memories, quantum repeaters, and eventually a full-scale quantum network.. Since the SPDC bandwidth is typically larger than the freespectral range (FSR) of the enhancement cavity, the resulting source has a multimode spectral characteristic.. Since the SPDC bandwidth is typically larger than the freespectral range (FSR) of the enhancement cavity, the resulting source has a multimode spectral characteristic.25–28 Additional filters such as filter cavities, atomic line filters, and wavelength-division multiplexers have been employed to suppress these unwanted modes. Reaching the necessary doubly resonant condition for the cluster effect is not trivial and has been mainly attempted at highly nondegenerate SPDC, or has not been sufficient to directly generate single mode narrow-band photons comparable to atomic transitions yet.. We report a novel approach to reach doubly resonant condition by inserting an additional birefringent crystal in a type-II OPO and tuning the clustering independent of the SPDC phase-matching. Our mode-selection scheme minimizes photon losses because of the additional filtering and enhancing the generation rate, which leads to an detectable four-fold coincidence rate from our source
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