Selected publications by Martin Felle

@article{muller_quantum_2018,
	title = {A quantum light-emitting diode for the standard telecom window around 1,550 nm},
	volume = {9},
	copyright = {2018 The Author(s)},
	issn = {2041-1723},
	url = {https://www.nature.com/articles/s41467-018-03251-7},
	doi = {10.1038/s41467-018-03251-7},
	abstract = {Single photons and entangled photon pairs are a key resource of many quantum secure communication and quantum computation protocols, and non-Poissonian sources emitting in the low-loss wavelength region around 1,550 nm are essential for the development of fibre-based quantum network infrastructure. However, reaching this wavelength window has been challenging for semiconductor-based quantum light sources. Here we show that quantum dot devices based on indium phosphide are capable of electrically injected single photon emission in this wavelength region. Using the biexciton cascade mechanism, they also produce entangled photons with a fidelity of 87 ± 4\%, sufficient for the application of one-way error correction protocols. The material system further allows for entangled photon generation up to an operating temperature of 93 K. Our quantum photon source can be directly integrated with existing long distance quantum communication and cryptography systems, and provides a promising material platform for developing future quantum network hardware.},
	language = {en},
	number = {1},
	urldate = {2020-08-22},
	journal = {Nature Communications},
	author = {Müller, T. and Skiba-Szymanska, J. and Krysa, A. B. and Huwer, J. and Felle, M. and Anderson, M. and Stevenson, R. M. and Heffernan, J. and Ritchie, D. A. and Shields, A. J.},
	month = feb,
	year = {2018}
    Publisher: {Nature Publishing Group},
	pages = {862}
    }

@phdthesis{felle_telecom_2017,
	type = {Thesis},
	title = {Telecom {Wavelength} {Quantum} {Devices}},
	copyright = {Attribution 4.0 International},
	url = {https://www.repository.cam.ac.uk/handle/1810/270019},
	abstract = {Semiconductor quantum dots (QDs) are well established as sub-Poissonian sources of entangled photon pairs. To improve the utility of a QD light source, it would be advantageous to extend their emission further into the near infrared, into the low absorption wavelength windows utilised in long-haul optical telecommunication.
Initial experiments succeeded in interfering O-band (1260—1360 nm) photons from an InAs/GaAs QD with dissimilar photons from a laser, an important mechanism for quantum teleportation. Interference visibilities as high as 60 ± 6 \% were recorded, surpassing the 50 \% threshold imposed by classical electrodynamics. Later, polarisation-entanglement of a similar QD was observed, with pairs of telecom-wavelength photons from the radiative cascade of the biexciton state exhibiting fidelities of 92.0 ± 0.2 \% to the  Bell state. 
Subsequently, an O-band telecom-wavelength quantum relay was realised. Again using an InAs/GaAs QD device, this represents the first implementation of a sub-Poissonian telecom-wavelength quantum relay, to the best knowledge of the author. The relay proved capable of implementing the famous four-state BB84 protocol, with a mean teleportation fidelity as high as 94.5 ± 2.2 \%, which would contribute 0.385 secure bits per teleported qubit. After characterisation by way of quantum process tomography, the performance of the relay was also evaluated to be capable of implementing a six-state QKD protocol. 
In an effort to further extend the emitted light from a QD into the telecom C-band 
(1530—1565 nm), alternative material systems were investigated. InAs QDs on a substrate of InP were shown to emit much more readily in the fibre-telecom O- and C-bands than their InAs/GaAs counterparts, largely due to the reduced lattice mismatch between the QD and substrate for InAs/InP ({\textasciitilde}3 \%) compared to InAs/GaAs ({\textasciitilde}7 \%). Additionally, to minimize the fine structure splitting (FSS) of the exciton level, which deteriorates the observed polarisation-entanglement, a new mode of dot growth was investigated. Known as droplet epitaxy (D-E), QDs grown in this mode showed a fourfold reduction in the FSS compared to dots grown in the Stranski-Krastanow mode. This improvement would allow observation of polarisation-entanglement in the telecom C-band. In subsequent work performed by colleagues at the Toshiba Cambridge Research Labs, these D-E QDs were embedded in a p-i-n doped optical cavity, processed with electrical contacts, and found to emit entangled pairs of photons under electrical excitation. 
The work of this thesis provides considerable technological advances to the field of entangled-light sources, that in the near future may allow for deterministic quantum repeaters operating at megahertz rates, and in the further future could facilitate the distribution of coherent multipartite states across a distributed quantum network.},
	language = {en},
	urldate = {2020-08-22},
	school = {University of Cambridge},
	author = {Felle, Martin Connor Patrick},
	month = dec,
	year = {2017},
	doi = {10.17863/CAM.16859}

@article{huwer_quantum-dot-based_2017,
	title = {Quantum-{Dot}-{Based} {Telecommunication}-{Wavelength} {Quantum} {Relay}},
	volume = {8},
	copyright = {All rights reserved},
	url = {https://link.aps.org/doi/10.1103/PhysRevApplied.8.024007},
	doi = {10.1103/PhysRevApplied.8.024007},
	abstract = {The development of quantum relays for long-haul and attack-proof quantum communication networks operating with weak coherent laser pulses requires entangled photon sources at telecommunication wavelengths with intrinsic single-photon emission for most practical implementations. Using a semiconductor quantum dot emitting entangled photon pairs in the telecommunication O band, we demonstrate a quantum relay fulfilling both of these conditions. The system achieves a maximum fidelity of 94.5\% for implementation of a standard four-state protocol with input states generated by a laser. We further investigate robustness against frequency detuning of the narrow-band input and perform process tomography of the teleporter, revealing operation for arbitrary pure input states, with an average gate fidelity of 83.6\%. The results highlight the potential of semiconductor light sources for compact and robust quantum-relay technology that is compatible with existing communication infrastructures.},
	number = {2},
	urldate = {2020-08-22},
	journal = {Physical Review Applied},
	author = {Huwer, J. and Stevenson, R. M. and Skiba-Szymanska, J. and Ward, M. B. and Shields, A. J. and Felle, M. and Farrer, I. and Ritchie, D. A. and Penty, R. V.},
	month = aug,
	year = {2017},
	note = {Publisher: American Physical Society}}

@article{skiba-szymanska_universal_2017,
	title = {Universal {Growth} {Scheme} for {Quantum} {Dots} with {Low} {Fine}-{Structure} {Splitting} at {Various} {Emission} {Wavelengths}},
	volume = {8},
	url = {https://link.aps.org/doi/10.1103/PhysRevApplied.8.014013},
	doi = {10.1103/PhysRevApplied.8.014013},
	abstract = {Efficient sources of individual pairs of entangled photons are required for quantum networks to operate using fiber-optic infrastructure. Entangled light can be generated by quantum dots (QDs) with naturally small fine-structure splitting (FSS) between exciton eigenstates. Moreover, QDs can be engineered to emit at standard telecom wavelengths. To achieve sufficient signal intensity for applications, QDs have been incorporated into one-dimensional optical microcavities. However, combining these properties in a single device has so far proved elusive. Here, we introduce a growth strategy to realize QDs with small FSS in the conventional telecom band, and within an optical cavity. Our approach employs ‘‘droplet-epitaxy’’ of InAs quantum dots on (001) substrates. We show the scheme improves the symmetry of the dots by 72\%. Furthermore, our technique is universal, and produces low FSS QDs by molecular beam epitaxy on GaAs emitting at ∼900 nm, and metal-organic vapor-phase epitaxy on InP emitting at ∼1550 nm, with mean FSS 4× smaller than for Stranski-Krastanow QDs.},
	number = {1},
	urldate = {2020-08-22},
	journal = {Physical Review Applied},
	author = {Skiba-Szymanska, Joanna and Stevenson, R. Mark and Varnava, Christiana and Felle, Martin and Huwer, Jan and Müller, Tina and Bennett, Anthony J. and Lee, James P. and Farrer, Ian and Krysa, Andrey B. and Spencer, Peter and Goff, Lucy E. and Ritchie, David A. and Heffernan, Jon and Shields, Andrew J.},
	month = jul,
	year = {2017},
	Publisher: {American Physical Society}
}

@article{al-khuzheyri_resonance_2016,
	title = {Resonance fluorescence from a telecom-wavelength quantum dot},
	volume = {109},
	issn = {0003-6951},
	url = {https://aip.scitation.org/doi/full/10.1063/1.4965845},
	doi = {10.1063/1.4965845},
	abstract = {We report on resonance fluorescence from a single quantum dot emitting at telecom wavelengths. We perform high-resolution spectroscopy and observe the Mollow triplet in the Rabi regime—a hallmark of resonance fluorescence. The measured resonance-fluorescence spectra allow us to rule out pure dephasing as a significant decoherence mechanism in these quantum dots. Combined with numerical simulations, the experimental results provide robust characterisation of charge noise in the environment of the quantum dot. Resonant control of the quantum dot opens up new possibilities for the on-demand generation of indistinguishable single photons at telecom wavelengths as well as quantum optics experiments and direct manipulation of solid-state qubits in telecom-wavelength quantum dots.},
	number = {16},
	urldate = {2020-08-22},
	journal = {Applied Physics Letters},
	author = {Al-Khuzheyri, R. and Dada, A. C. and Huwer, J. and Santana, T. S. and Skiba-Szymanska, J. and Felle, M. and Ward, M. B. and Stevenson, R. M. and Farrer, I. and Tanner, M. G. and Hadfield, R. H. and Ritchie, D. A. and Shields, A. J. and Gerardot, B. D.},
	month = oct,
	year = {2016},
	note = {Publisher: American Institute of Physics}
}

@article{felle_interference_2015,
	title = {Interference with a quantum dot single-photon source and a laser at telecom wavelength},
	volume = {107},
	issn = {0003-6951},
	url = {https://aip.scitation.org/doi/abs/10.1063/1.4931729},
	doi = {10.1063/1.4931729},
	number = {13},
	urldate = {2020-08-22},
	journal = {Applied Physics Letters},
	author = {Felle, M. and Huwer, J. and Stevenson, R. M. and Skiba-Szymanska, J. and Ward, M. B. and Farrer, I. and Penty, R. V. and Ritchie, D. A. and Shields, A. J.},
	month = sep,
	year = {2015},
	note = {Publisher: American Institute of Physics}
}

@article{sharma_density_2015,
	title = {Density dependent composition of {InAs} quantum dots extracted from grazing incidence x-ray diffraction measurements},
	volume = {5},
	copyright = {2015 The Author(s)},
	issn = {2045-2322},
	url = {https://www.nature.com/articles/srep15732},
	doi = {10.1038/srep15732},
	abstract = {Epitaxial InAs quantum dots grown on GaAs substrate are being used in several applications ranging from quantum communications to solar cells. The growth mechanism of these dots also helps us to explore fundamental aspects of self-organized processes. Here we show that composition and strain profile of the quantum dots can be tuned by controlling in-plane density of the dots over the substrate with the help of substrate-temperature profile. The compositional profile extracted from grazing incidence x-ray measurements show substantial amount of inter-diffusion of Ga and In within the QD as a function of height in the low-density region giving rise to higher variation of lattice parameters. The QDs grown with high in-plane density show much less spread in lattice parameter giving almost flat density of In over the entire height of an average QD and much narrower photoluminescence (PL) line. The results have been verified with three different amounts of In deposition giving systematic variation of the In composition as a function of average quantum dot height and average energy of PL emission.},
	language = {en},
	number = {1},
	urldate = {2020-08-22},
	journal = {Scientific Reports},
	author = {Sharma, Manjula and Sanyal, Milan K. and Farrer, Ian and Ritchie, David A. and Dey, Arka B. and Bhattacharyya, Arpan and Seeck, Oliver H. and Skiba-Szymanska, Joanna and Felle, Martin and Bennett, Anthony J. and Shields, Andrew J.},
	month = oct,
	year = {2015},
	note = {Publisher: Nature Publishing Group}
}