Abstract
We report 100% duty cycle generation of sub-MHz single photon pairs at the rubidium D1 line using cavity-enhanced spontaneous parametric downconversion. The temporal intensity cross correlation function exhibits a bandwidth of 666±16 kHz for the single photons, an order of magnitude below the natural linewidth of the target transition. A half-wave plate inside our cavity helps to achieve triple resonance between pump, signal, and idler photon, reducing the bandwidth and simplifying the locking scheme. Additionally, stabilisation of the cavity to the pump frequency enables the 100% duty cycle. The quantum nature of the source is confirmed by the idler-triggered second-order autocorrelation function at τ=0 to be gs,s(2)(0)= 0.016±0.002 for a heralding rate of 5 kHz. The generated photons are well-suited for storage in quantum memory schemes with sub-natural linewidths, such as gradient echo memories.
Highlights
Quantum technologies are primed to revolutionise information processing, with large companies already investing in basic quantum computing devices
The absence of high fidelity entangling gates in linear optical quantum computing (LOQC) and true on-demand sources means that the repeater node will require noiseless amplification as well as a memory to hold the photonic qubit
As the spectral properties of the memories are limited in their tunability, the single photon source needs to be engineered to match the wavelength and the bandwidth of the atomic transition
Summary
Quantum technologies are primed to revolutionise information processing, with large companies already investing in basic quantum computing devices. As the spectral properties of the memories are limited in their tunability, the single photon source needs to be engineered to match the wavelength and the bandwidth of the atomic transition.
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