Quantum teleportation using highly coherent emission from telecom C-band quantum dots

Abstract

A practical way to link separate nodes in quantum networks is to send photons over the standard telecom fibre network. This requires sub-Poissonian photon sources in the telecom wavelength band around 1550 nm, where the photon coherence time has to be sufficient to enable the many interference-based technologies at the heart of quantum networks. Here, we show that droplet epitaxy InAs/InP quantum dots emitting in the telecom C-band can provide photons with coherence times exceeding 1 ns even under non-resonant excitation, more than a factor two longer than values reported for shorter wavelength quantum dots under similar conditions. We demonstrate that these coherence times enable near-optimal interference with a C-band laser qubit, with visibilities only limited by the quantum dot multiphoton emission. Using entangled photons, we further show teleportation of such qubits in six different bases with average fidelity reaching 88.3±4%. Beyond direct applications in long-distance quantum communication, the high degree of coherence in these quantum dots is promising for future spin based telecom quantum network applications.

Quantum teleportation with imperfect quantum dots

“…Semiconductor quantum dots (QDs) are a promising candidate for achieving on-demand operation 9 . In recent years, entangled QD photons have been used in seminal demonstrations of quantum teleportation to transfer qubits encoded in either an attenuated laser pulse [10][11][12] or a single photon generated on demand by the same QD 13 . While these results paved the way for the following generation of four-photon experiments 14,15 , imperfections of the source still played a significant role in forcing to either work at low values of protocol fidelity or with narrow temporal post-selection.…”

A tuneable telecom wavelength entangled light emitting diode deployed in an installed fibre network

“…Higher photon collection efficiencies could be achieved by implementing nano-photonic structures such as in-plane circular Bragg reflectors [49][50][51] , broadband optical antennas 52 or microlenses 53 while charge control of QDs 54 via optimisation of the tuning diode might open up the route for higher photon generation efficiencies as required for deterministic operation. Furthermore, QDs grown by so-called droplet epitaxy are a highly promising alternative to S-K grown QDs as they show extremely good coherence properties even for non-resonant optical excitation 19 .…”

“…In contrast, non-resonant excitation schemes are much simpler to implement and integrate, making them a welcome testbed for first steps into network integration of quantum light emitters. Of course, this comes at the expense of lower efficiency 17 and photon purities, but with performances still good enough for experiments such as quantum teleportation with electrically 18 and optically 19 injected sources. For quantum communication applications, careful engineering of material compositions and wafer growth conditions have enabled fabrication of QDs emitting in the standard telecom wavelength bands [20][21][22][23] , recently enabling for the first time the transmission of photons from a single quantum emitter over a deployed standard network fibre 24 .…”

InP-Substrate-Based Quantum Dashes on a DBR as Single-Photon Emitters at the Third Telecommunication Window

“…On the other hand, droplet epitaxy approach enabling reduction in surface density has been presented [49], also using the MBE technology [51]. Emission of single photons with electrical excitation in the diode structure [61], as well as the possibility of obtaining entangled photons and quantum teleportation of qubits have been demonstrated for nanostructures of that kind [62].…”