Publications


Efficient Classical Algorithm for Boson Sampling with Partially Distinguishable Photons.

Phys Rev Lett 120 (2018) 220502-220502

JJ Renema, A Menssen, WR Clements, G Triginer, WS Kolthammer, IA Walmsley

We demonstrate how boson sampling with photons of partial distinguishability can be expressed in terms of interference of fewer photons. We use this observation to propose a classical algorithm to simulate the output of a boson sampler fed with photons of partial distinguishability. We find conditions for which this algorithm is efficient, which gives a lower limit on the required indistinguishability to demonstrate a quantum advantage. Under these conditions, adding more photons only polynomially increases the computational cost to simulate a boson sampling experiment.


Characterization of ultrashort laser pulses employing self-phase modulation dispersion-scan technique

Journal of Optics Institute of Physics Publishing 20 (2018) 035502

AB Sharba, O Chekhlov, AS Wyatt, R Pattathil, M Borghesi, G Sarri

We present a new phase characterization technique for ultrashort laser pulses that employs self-phase modulation (SPM) in the dispersion scan approach. The method can be implemented by recording a set of nonlinearly modulated spectra generated with a set of known chirp values. The unknown phase of the pulse is retrieved by linking the recorded spectra to the initial spectrum of the pulse via a phase function guessed by a function minimization iterative algorithm. This technique has many advantages over the dispersion scan techniques that use frequency conversion processes. Mainly, the use of SPM cancels out the phase and group velocity mismatch errors and dramatically widens the spectral acceptance of the nonlinear medium and the range of working wavelength. The robustness of the technique is demonstrated with smooth and complex phase retrievals using numerical examples. The method is shown to be not affected by the spatial distribution of the beam or the presence of nonlinear absorption process. In addition, we present an efficient method for phase representation based on a summation of a set of Gaussian functions. The independence of the functions from each other prevents phase coupling of any kind and facilitates a flexible phase representation.


High-speed noise-free optical quantum memory

PHYSICAL REVIEW A 97 (2018) ARTN 042316

KT Kaczmarek, PM Ledingham, B Brecht, SE Thomas, GS Thekkadath, O Lazo-Arjona, JHD Munns, E Poem, A Feizpour, DJ Saunders, J Nunn, IA Walmsley


All-fiber Single Photon Sources

Specialty Optical Fibers 2018 (2018)

RJA FRANCIS-JONES


Quantum interference beyond the fringe.

Science (New York, N.Y.) 358 (2017) 1001-1002

I Walmsley


A Noiseless Quantum Optical Memory at Room Temperature

2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC) (2017)

PM Ledingham, KT Kaczmarek, B Brecht, A Feizpour, GS Thekkadath, SE Thomas, JHD Munns, DJ Saunders, J Nunn, IA Walmsley, IEEE


Temporal-mode selection with a Raman quantum memory

Optics InfoBase Conference Papers Part F66-FiO 2017 (2017)

JHD Munns, SE Thomas, KT Kaczmarek, PM Ledingham, DJ Saunders, J Nunn, B Brecht, IA Walmsley

© OSA 2017. Temporal modes (TMs) of pulsed single-photon states have been identified as appealing basis states for quantum information science. Recent work has seen progress towards TM-selective operations based on nonlinear optics. Here, we demonstrate for the first time a linear TM-selective device, namely a Raman quantum memory in warm atomic Caesium vapour. We achieve switching fidelities of 86.5% when operating the memory with ns-duration pulses. These results pave the way towards new quantum information applications, where TM-selection, TM-reshaping, and network synchronisation are achieved with one single device.


Novel Interactions of Dissipative Kerr Solitons in Nonlinear Cavity Networks

2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC) (2017)

JHD Munns, IA Walmsley, YH Wen, IEEE


A noiseless quantum optical memory at room temperature

Optics InfoBase Conference Papers Part F81-EQEC 2017 (2017)

PM Ledingham, KT Kaczmarek, B Brecht, A Feizpour, GS Thekkadath, SE Thomas, JHD Munns, DJ Saunders, J Nunn, IA Walmsley


Combined visible and near-infrared OPA for wavelength scaling experiments in strong-field physics

NONLINEAR FREQUENCY GENERATION AND CONVERSION: MATERIALS AND DEVICES XVI 10088 (2017)

DT Lloyd, K O'Keeffe, AS Wyatt, PN Anderson, D Treacher, SM Hooker


Temporal amplitude & phase: Algorithmic reconstruction via time-domain interferometry (TeAPARTI)

Optics InfoBase Conference Papers Part F66-FiO 2017 (2017)

JHD Munns, S Park, B Brecht, IA Walmsley

© OSA 2017. We introduce a novel pulse characterisation schemeTeAPARTIwhich facilitates single-shot amplitude and phase characterisation of nanosecond duration pulses. This regime has so far been inaccessible but is crucial for optimising quantum memories. We demonstrate the generation of shaped nanosecond pulses with an electro-optic modulator and their successive characterisation with TeAPARTI.


QLad: A noise-free quantum memory for broadband light at room temperature

2017 Conference on Lasers and Electro-Optics, CLEO 2017 - Proceedings 2017-January (2017) 1-2

KT Kaczmarek, PM Ledingham, B Brecht, A Feizpour, GS Thekkadath, SE Thomas, JHD Munns, DJ Saunders, IA Walmsley, J Nunn

© 2017 IEEE. We implement a low-noise, broadband quantum memory for light via off-resonant two-photon absorption in warm atomic vapour. We store heralded single photons and verify that the retrieved fields are anti-bunched.


Theory of noise suppression in Lambda-type quantum memories by means of a cavity

PHYSICAL REVIEW A 96 (2017) ARTN 012338

J Nunn, JHD Munns, S Thomas, KT Kaczmarek, C Qiu, A Feizpour, E Poem, B Brecht, DJ Saunders, PM Ledingham, DV Reddy, MG Raymer, IA Walmsley


Quantum Correlations between Single Telecom Photons and a Multimode On-Demand Solid-State Quantum Memory

PHYSICAL REVIEW X 7 (2017) ARTN 021028

A Seri, A Lenhard, D Rielander, M Gundogan, PM Ledingham, M Mazzera, H de Riedmatten


A noise-free quantum memory for broadband light at room temperature

Optics InfoBase Conference Papers Part F73-QIM 2017 (2017)

KT Kaczmarek, PM Ledingham, B Brecht, A Feizpour, GS Thekkadath, SE Thomas, JHD Munns, DJ Saunders, IA Walmsley, J Nunn

© OSA 2017. We have developed a novel protocol for broadband, noise-free light-matter interactions using off-resonant two-photon absorption. We have successfully stored and retrieved 1.5 GHz bandwidth heralded single photons in warm cesium vapour, measuring a g(2)h= 0:39±0:05.


Experimental demonstration of nonbilocal quantum correlations.

Science advances 3 (2017) e1602743-

DJ Saunders, DJ Saunders, AJ Bennet, C Branciard, GJ Pryde

Quantum mechanics admits correlations that cannot be explained by local realistic models. The most studied models are the standard local hidden variable models, which satisfy the well-known Bell inequalities. To date, most works have focused on bipartite entangled systems. We consider correlations between three parties connected via two independent entangled states. We investigate the new type of so-called "bilocal" models, which correspondingly involve two independent hidden variables. These models describe scenarios that naturally arise in quantum networks, where several independent entanglement sources are used. Using photonic qubits, we build such a linear three-node quantum network and demonstrate nonbilocal correlations by violating a Bell-like inequality tailored for bilocal models. Furthermore, we show that the demonstration of nonbilocality is more noise-tolerant than that of standard Bell nonlocality in our three-party quantum network.


QLad: A Noise-Free Quantum Memory for Broadband Light at Room Temperature

2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) (2017)

KT Kaczmarek, PM Ledingham, B Brecht, A Feizpour, GS Thekkadath, SE Thomas, JHD Munns, DJ Saunders, IA Walmsley, J Nunn, IEEE


High efficiency Raman memory by suppressing radiation trapping

NEW JOURNAL OF PHYSICS 19 (2017) ARTN 063034

SED Thomas, JHD Munns, KT Kaczmarek, C Qiu, B Brecht, A Feizpour, PM Ledingham, IA Walmsley, J Nunn, DJ Saunders


Chip-based array of near-identical, pure, heralded single-photon sources

OPTICA 4 (2017) 90-96

JB Spring, PL Mennea, BJ Metcalf, PC Humphreys, JC Gates, HL Rogers, C Soller, BJ Smith, WS Kolthammer, PGR Smith, IA Walmsley


Distinguishability and Many-Particle Interference.

Physical review letters 118 (2017) 153603-

AJ Menssen, AE Jones, BJ Metcalf, MC Tichy, S Barz, WS Kolthammer, IA Walmsley

Quantum interference of two independent particles in pure quantum states is fully described by the particles' distinguishability: the closer the particles are to being identical, the higher the degree of quantum interference. When more than two particles are involved, the situation becomes more complex and interference capability extends beyond pairwise distinguishability, taking on a surprisingly rich character. Here, we study many-particle interference using three photons. We show that the distinguishability between pairs of photons is not sufficient to fully describe the photons' behavior in a scattering process, but that a collective phase, the triad phase, plays a role. We are able to explore the full parameter space of three-photon interference by generating heralded single photons and interfering them in a fiber tritter. Using multiple degrees of freedom-temporal delays and polarization-we isolate three-photon interference from two-photon interference. Our experiment disproves the view that pairwise two-photon distinguishability uniquely determines the degree of nonclassical many-particle interference.

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