Abstract
Quantum networks are essential for realising distributed quantum computation and quantum communication. Entangled photons are a key resource, with applications such as quantum key distribution, quantum relays, and quantum repeaters. All components integrated in a quantum network must be synchronised and therefore comply with a certain clock frequency. In quantum key distribution, the most mature technology, clock rates have reached and exceeded 1GHz. Here we show the first electrically pulsed sub-Poissonian entangled photon source compatible with existing fiber networks operating at this clock rate. The entangled LED is based on InAs/InP quantum dots emitting in the main telecom window, with a multi-photon probability of less than 10% per emission cycle and a maximum entanglement fidelity of 89%. We use this device to demonstrate GHz clocked distribution of entangled qubits over an installed fiber network between two points 4.6km apart.
Highlights
Entangled LED (ELED) telecom C-band sources have been demonstrated with DC excitation [16]
The entangled LED is based on InAs/InP quantum dots emitting in the main telecom window, with a multi-photon probability of less than 10% per emission cycle and a maximum entanglement fidelity of 89%
Pulsed single [13, 17, 18] and entangled [9, 14, 19,20,21,22] photon sources based on semiconductor quantum dots (QD) have been developed but are either at short wavelengths, and incompatible with existing fiber networks, or only operate at repetition rates too slow for current quantum network applications
Summary
To assess the performance of the pulsed ELED with these non-research grade detectors, we position a single 168ps integration window to give maximum entanglement fidelity, shown as a black dashed box in figure 3(c). This results in a fidelity of 0.86±0.14, in the regime compatible with error correction in quantum key distribution applications [28]. Maximum entanglement fidelity for sets of 2 hours of data It remains around 0.79 for the entire 14 hour experiment, demonstrating the excellent stability of the 1GHz clocked ELED as a source for distributed entangled photon pairs across a real-world fiber network. Pulsed operation with a common telecommunication clock frequency opens up the possibility for seamless integration with other quantum network hardware such as QKD systems and efficient time multiplexing with classical communication signals
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