# Publications by Jamie Francis-Jones

## All-fiber single photon sources - modal control for active routing

Optics InfoBase Conference Papers Part F111-SOF 2018 (2018)

RJA Francis-Jones, RA Hoggarth, OR Gibson, PJ Mosley

© 2018 The Author(s). Speciality fiber has enabled the development of fully-integrated heralded single-photon sources incorporating feedforward and active switching to enhance performance. We present recent results and future directions.

## Two-Way Photonic Interface for Linking the Sr+ Transition at 422 nm to the Telecommunication C Band

PHYSICAL REVIEW APPLIED 10 (2018) ARTN 044012

TA Wright, RJA Francis-Jones, CBE Gawith, JN Becker, PM Ledingham, PGR Smith, J Nunn, PJ Mosley, B Brecht, IA Walmsley

## Resource-efficient fibre-integrated temporal multiplexing of heralded single photons

JOURNAL OF OPTICS 19 (2017) ARTN 125503

RA Hoggarth, RJA Francis-Jones, PJ Mosley

## Fibre-integrated noise gating of high-purity heralded single photonsE

JOURNAL OF OPTICS 19 (2017) ARTN 104005

RJA Francis-Jones, PJ Mosley

## All-fiber multiplexed source of high-purity single photons

OPTICA 3 (2016) 1270-1273

RJA Francis-Jones, RA Hoggarth, PJ Mosley

## Characterisation of longitudinal variation in photonic crystal fibre.

Optics express 24 (2016) 24836-24845

RJA Francis-Jones, PJ Mosley

We present a method by which the degree of longitudinal variation in photonic crystal fibre (PCF) may be characterised through seeded four-wave mixing (FWM). Using an iterative numerical reconstruction, we created a theoretical model of the PCF that displays FWM phasematching properties that are similar to experiment across all measured length scales. Our results demonstrate that the structure of our PCF varies by less than ±1 % and that the characteristic length of the variations is approximately 15 cm.

## Characterizing the variation of propagation constants in multicore fiber.

Optics express 22 (2014) 25689-25699

PJ Mosley, I Gris-Sánchez, JM Stone, RJA Francis-Jones, DJ Ashton, TA Birks

We demonstrate a numerical technique that can evaluate the core-to-core variations in propagation constant in multicore fiber. Using a Markov Chain Monte Carlo process, we replicate the interference patterns of light that has coupled between the cores during propagation. We describe the algorithm and verify its operation by successfully reconstructing target propagation constants in a fictional fiber. Then we carry out a reconstruction of the propagation constants in a real fiber containing 37 single-mode cores. We find that the range of fractional propagation constant variation across the cores is approximately ± 2 × 10(-5).

## Photon-pair generation in photonic crystal fibre with a 1.5 GHz modelocked VECSEL

OPTICS COMMUNICATIONS 327 (2014) 39-44

OJ Morris, RJA Francis-Jones, KG Wilcox, AC Tropper, PJ Mosley

## Engineered photon-pair generation by four-wave mixing in asymmetric coupled waveguides

ArXiv (0)

RJA Francis-Jones, TA Wright, AV Gorbach, PJ Mosley

Third-order nonlinear processes require phase matching between the interacting fields to achieve high efficiencies. Typically in guided-wave $\chi^{(3)}$ platforms this is achieved by engineering the dispersion of the modes through the transverse profile of the device. However, this limits the flexibility of the phase matching that can be achieved. Instead, we analyze four-wave mixing in a pair of asymmetric waveguides and show that phasematching may be achieved in any $\chi^{(3)}$ waveguide by coupling of a nondegenerate pump from an adjacent waveguide. We demonstrate the additional flexibility that this approach yields in the case of photon-pair generation by spontaneous FWM, where the supermode dispersion may be modified to produce pure heralded single photons -- a critical capability required for example by silicon platforms for chip-scale quantum photonics.

## Birefringent anti-resonant hollow-core fiber

ArXiv (0)

S Yerolatsitis, R Shurvinton, P Song, Y Zhang, JA Francis-Jones, KR Rusimova

Hollow-core fibers have demonstrated record performance in applications such as high-power pulse delivery, quantum computing, and sensing. However, their routine use is yet to become reality. A major obstacle is the ability to maintain the polarization state of light over a broad range of wavelengths, while also ensuring low attenuation and single-mode guidance. Here we simulated, fabricated and characterized a single-mode polarization-maintaining anti-resonant hollow-core fiber. The birefringence was achieved by introducing resonators of different thicknesses, thereby creating reduced symmetry in the structure. The measured group birefringence of 4.4x10-5 at 1550 nm is in good agreement with the calculated group birefringence from the simulations. This corresponds to a phase birefringence of 2.5x10-5 at 1550 nm. The measured loss of the fiber was 0.46 dB/m at 1550 nm. With its simple structure, low loss, and broadband operation this polarization-maintaining anti-resonant hollow-core fiber is a serious contender for applications in gas-based nonlinear optics and communications.

## Spectrally pure single photons at telecommunications wavelengths using commercial birefringent optical fiber

ArXiv (0)

J Lugani, RJA Francis-Jones, J Boutari, IA Walmsley

We report a bright and tunable source of spectrally pure heralded single photons in the telecom O-Band, based on cross-polarized four wave mixing in a commercial birefringent optical fiber. The source can achieve a purity of 85%, heralding efficiency of 30% and high coincidences to accidentals ratio of 108. Furthermore, the possibility of building multiple identical sources is explored. Through the measurements of joint spectral intensities, we find that the fiber is homogeneous over atleast 45 centimeters and can potentially realize 4 identical sources. This paves the way for a cost-effective fiber-optic approach to implement multi-photon quantum optics experiments.

## Temporal Loop Multiplexing: A resource efficient scheme for multiplexed photon-pair sources

ArXiv (0)

RJA Francis-Jones, PJ Mosley

Single photons are a vital resource for photonic quantum information processing. However, even state-of-the-art single photon sources based on photon-pair generation and heralding detection have only a low probability of delivering a single photon when one is requested. We analyse a scheme that uses a switched fibre delay loop to increase the delivery probability per time bin of single photons from heralded sources. We show that, for realistic experimental parameters, combining the output of up to 15 pulses can yield a performance improvement of a factor of 10. We consider the future performance of this scheme with likely component improvements.

## Exploring the limits of multiplexed photon-pair sources for the preparation of pure single-photon states

ArXiv (0)

RJA Francis-Jones, PJ Mosley

Current sources of heralded single photons based on nonlinear optics operate in a probabilistic manner. In order to build quantum-enhanced devices based around the use of single photons, compact, turn-key and deterministic sources are required. A possible solution is to multiplex a number of sources to increase the single-photon generation probability and in so doing reducing the waiting time to deliver large numbers of photons simultaneously, from independent sources. Previously it has been shown that, in the ideal case, 17 multiplexed sources allow deterministic generation of heralded single photons [Christ and Silberhorn, Phys. Rev. A 85, 023829 (2012)]. Here we extend this analysis to include undesirable effects of detector inefficiency and photon loss on a number of multiplexed sources using a variety of different detectors for heralding. We compare these systems for fixed signal-to-noise ratio to allow a direct comparison of performance for real- world heralded single photon sources.