Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA and Maryland NanoCenter, University of Maryland, College Park, Maryland, USA.
We show that quantum frequency conversion (QFC) can overcome the spectral distinguishability common to inhomogeneously broadened solid-state quantum emitters. QFC is implemented by combining single photons from an InAs/GaAs quantum dot (QD) at 980 nm with a 1550 nm pump laser in a periodically poled lithium niobate (PPLN) waveguide to generate photons at 600 nm with a signal-to-background ratio exceeding 100∶1. Photon correlation and two-photon interference measurements confirm that both the single photon character and wave packet interference of individual QD states are preserved during frequency conversion. Finally, we convert two spectrally separate QD transitions to the same wavelength in a single PPLN waveguide and show that the resulting field exhibits nonclassical two-photon interference.
[Show abstract][Hide abstract] ABSTRACT: We experimentally demonstrate a high-fidelity visible-to-telecommunication
wavelength conversion of a photon by using a solid-state-based difference
frequency generation. In the experiment, one half of a pico-second visible
entangled photon pair at 780 nm is converted to a 1522-nm photon, resulting in
the entangled photon pair between 780 nm and 1522 nm. Using superconducting
single-photon detectors with low dark count rates and small timing jitters, we
selectively observed well-defined temporal modes containing the two photons. We
achieved a fidelity of $0.93 \pm 0.04$ after the wavelength conversion,
indicating that our solid-state-based scheme can be used for faithful frequency
down-conversion of visible photons emitted from quantum memories composed of
Physical Review A 07/2012; 87(1). DOI:10.1103/PhysRevA.87.010301 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We demonstrate efficient (>30%) quantum frequency conversion of visible single photons (711 nm) emitted by a quantum dot to a telecom wavelength (1313 nm). Analysis of the first- and second-order coherence before and after wavelength conversion clearly proves that pivotal properties, such as the coherence time and photon antibunching, are fully conserved during the frequency translation process. Our findings underline the great potential of single photon sources on demand in combination with quantum frequency conversion as a promising technique that may pave the way for a number of new applications in quantum technology.
[Show abstract][Hide abstract] ABSTRACT: Long-distance quantum communication networks require appropriate interfaces between matter qubit-based nodes and low-loss photonic quantum channels. We implement a downconversion quantum interface, where the single photons emitted from a semiconductor quantum dot at 910 nm are downconverted to 1560 nm using a fiber-coupled periodically poled lithium niobate waveguide and a 2.2-μm pulsed pump laser. The single-photon character of the quantum dot emission is preserved during the downconversion process: we measure a cross-correlation g<sup>(2)</sup>(τ = 0) = 0.17 using resonant excitation of the quantum dot. We show that the downconversion interface is fully compatible with coherent optical control of the quantum dot electron spin through the observation of Rabi oscillations in the downconverted photon counts. These results represent a critical step towards a long-distance hybrid quantum network in which subsystems operating at different wavelengths are connected through quantum frequency conversion devices and 1.5-μm quantum channels.
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