1GHz clocked distribution of electrically generated entangled photon pairs

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, the current standard clock rate is 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.

Maximally entangled and GHz-clocked on-demand photon pair source

“…The raw entanglement negativities (fidelities) of up to 0.479 ± 0.005 (0.95 ± 0.01) are not limited by either the X fine structure or the XX−X-cascade process but only by the experimental quality of the polarization projection of the two-photon correlations. Contrary to recent publications claiming GHz-clocked entangled photon pair sources [17,18] no reset of the XX−X-cascade is required, which is also a necessary condition for fully on-demand entangled photon pair sources. We present a significantly enhanced method of determining η ex and η det directly from two-photon correlation data with a minimal set of assumptions.…”

“…Semiconductor quantum dots (QDs) feature attractive properties such as interoperability with existing semiconductor miniaturization technology, flexibility in emission wavelength and high potential clock rates. Even though exploiting the latter in both theoretical entanglement distribution protocols [9,16] and experimental implementations [17,18] has been a strong focus of recent activities, a device that addresses all required parameters is sorely lacking. With the exception of the quantum memory storage, we aim to address last-mentioned point in this study.…”

Quantum Communication Using Semiconductor Quantum Dots

“…The generation of entangled photons at a wavelength of 1550 nm from a QD SPS has already been shown in experiments by Olbrich et al [171]. While in their experiment the quantum emitter was optically excited with a continuous-wave laser, Shooter et al recently realized a pulsed electrically excited QD-source generating entangled photon pairs at GHz clock rate in the Telecom C-band [172]. The entangled photon pairs showed a fidelity to the maximally entangled state of 89% and were distributed over a fiber link of 4.6 km length at record rates, representing an important step towards highperformance QKD systems exploiting sub-Poissonian entanglement sources.…”

Quantum Communication Using Semiconductor Quantum Dots

“…More recently, Shooter et al demonstrated a GHz-clocked electrically triggered QD entanglement source operating in the telecom Cband based on InAs droplet QDs grown on InP substrate. [235] The generated entangled photon pairs, showing a peak fidelity to the maximally entangled state of 89% after temporal post-selection, were distributed at record-high rates over a fiber link of 4.6 km length, representing an important step toward high-performance QKD systems exploiting sub-Poissonian entanglement sources. The same type of QDs has been used to demonstrate entanglement generation up to 93 K [193] -a temperature enabling operation at liquid nitrogen or the integration into compact Stirling cryocoolers [236] (see also Section 4.1).…”