Publications


Benchmarking of Gaussian boson sampling using two-point correlators

Physical Review A American Physical Society (APS) 99 (2019) 023836

DS Phillips, M Walschaers, JJ Renema, IA Walmsley, N Treps, J Sperling


Coherent Control and Wave Mixing in an Ensemble of Silicon-Vacancy Centers in Diamond.

Physical review letters 122 (2019) 063601-

C Weinzetl, J Görlitz, JN Becker, IA Walmsley, E Poem, J Nunn, C Becher

Strong light-matter interactions are critical for quantum technologies based on light, such as memories or nonlinear interactions. Solid state materials will be particularly important for such applications due to the relative ease of fabrication of components. Silicon vacancy centers (SiV^{-}) in diamond feature especially narrow inhomogeneous spectral lines, which are rare in solid materials. Here, we demonstrate resonant coherent manipulation, stimulated Raman adiabatic passage, and strong light-matter interaction via the four-wave mixing of a weak signal field in an ensemble of SiV^{-} centers.


An experimental quantum Bernoulli factory

Science Advances American Association for the Advancement of Science (AAAS) 5 (2019) eaau6668-eaau6668

RB Patel, T Rudolph, GJ Pryde

<jats:p>There has been a concerted effort to identify problems computable with quantum technology, which are intractable with classical technology or require far fewer resources to compute. Recently, randomness processing in a Bernoulli factory has been identified as one such task. Here, we report two quantum photonic implementations of a Bernoulli factory, one using quantum coherence and single-qubit measurements and the other one using quantum coherence and entangling measurements of two qubits. We show that the former consumes three orders of magnitude fewer resources than the best-known classical method, while entanglement offers a further fivefold reduction. These concepts may provide a means for quantum-enhanced performance in the simulation of stochastic processes and sampling tasks.</jats:p>


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.


Engineering a noiseless and broadband Raman quantum memory for temporal mode manipulation

Optics InfoBase Conference Papers Part F114-FIO 2018 (2018)

TM Hird, SE Thomas, JHD Munns, OL Arjona, S Gao, J Nunn, B Brecht, DJ Saunders, PM Ledingham, IA Walmsley

© 2018 The Author(s). The Raman quantum memory can manipulate temporal modes of light - a promising high-dimensional basis for quantum information processing. We demonstrate both temporal mode manipulation and a novel suppression scheme for four-wave mixing noise.


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 - 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.


Conclusive experimental demonstration of one-way Einstein-Podolsky-Rosen steering

Phys. Rev. Lett. 121 (2018) 100401-100401

N Tischler, F Ghafari, TJ Baker, S Slussarenko, RB Patel, MM Weston, S Wollmann, LK Shalm, VB Verma, SW Nam, HC Nguyen, HM Wiseman, GJ Pryde

Einstein-Podolsky-Rosen steering is a quantum phenomenon wherein one party influences, or steers, the state of a distant party's particle beyond what could be achieved with a separable state, by making measurements on one half of an entangled state. This type of quantum nonlocality stands out through its asymmetric setting, and even allows for cases where one party can steer the other, but where the reverse is not true. A series of experiments have demonstrated one-way steering in the past, but all were based on significant limiting assumptions. These consisted either of restrictions on the type of allowed measurements, or of assumptions about the quantum state at hand, by mapping to a specific family of states and analysing the ideal target state rather than the real experimental state. Here, we present the first experimental demonstration of one-way steering free of such assumptions. We achieve this using a new sufficient condition for non-steerability, and, although not required by our analysis, using a novel source of extremely high-quality photonic Werner states.


Challenging local realism with human choices

NATURE 557 (2018) 212-+

C Abellan, A Acin, A Alarcon, O Alibart, CK Andersen, F Andreoli, A Beckert, FA Beduini, A Bendersky, M Bentivegna, P Bierhorst, D Burchardt, A Cabello, J Carine, S Carrasco, G Carvacho, D Cavalcanti, R Chaves, J Cortes-Vega, A Cuevas, A Delgado, H de Riedmatten, C Eichler, P Farrera, J Fuenzalida, M Garcia-Matos, R Garthoff, S Gasparinetti, T Gerrits, FG Jouneghani, S Glancy, ES Gomez, P Gonzalez, J-Y Guan, J Handsteiner, J Heinsoo, G Heinze, A Hirschmann, O Jimenez, F Kaiser, E Knill, LT Knoll, S Krinner, P Kurpiers, MA Larotonda, J-A Larsson, A Lenhard, H Li, M-H Li, G Lima, B Liu, Y Liu, IH Lopez Grande, T Lunghi, X Ma, OS Magana-Loaiza, P Magnard, A Magnoni, M Marti-Prieto, D Martinez, P Mataloni, A Mattar, M Mazzera, RP Mirin, MW Mitchell, S Nam, M Oppliger, J-W Pan, RB Patel, GJ Pryde, D Rauch, K Redeker, D Rielander, M Ringbauer, T Roberson, W Rosenfeld, Y Salathe, L Santodonato, G Sauder, T Scheidl, CT Schmiegelow, F Sciarrino, A Seri, LK Shalm, S-C Shi, S Slussarenko, MJ Stevens, S Tanzilli, F Toledo, J Tura, R Ursin, P Vergyris, VB Verma, T Walter, A Wallraff, Z Wang, H Weinfurter, MM Weston, AG White, C Wu, GB Xavier, L You, X Yuan, A Zeilinger, Q Zhang, W Zhang, J Zhong, BIGBT Collaboration


Strong Unitary and Overlap Uncertainty Relations: Theory and Experiment

PHYSICAL REVIEW LETTERS 120 (2018) ARTN 230402

K-W Bong, N Tischler, RB Patel, S Wollmann, GJ Pryde, MJW Hall


Single-photon-level interface for linking Sr<sup>+</sup>transition at 422nm with the telecommunications C-band

2018 Conference on Lasers and Electro-Optics, CLEO 2018 - Proceedings (2018)

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

© 2018 OSA. We present a single-stage bi-directional interface capable of linking Sr+trapped ion qubits emitting single photons at 422 nm with the telecoms C-band. We achieve external up(down) conversion efficiencies of 9.4%(1.1%).


Single-photon-level interface for linking Sr<sup>+</sup> transition at 422nm with the telecommunications C-band

Optics InfoBase Conference Papers Part F92-CLEO_AT 2018 (2018)

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

© OSA 2018. We present a single-stage bi-directional interface capable of linking Sr+ trapped ion qubits emitting single photons at 422 nm with the telecoms C-band. We achieve external up(down) conversion efficiencies of 9.4%(1.1%).


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


A noiseless quantum optical memory at room temperature

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

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

© OSA 2017. Quantum optical memories are devices that store quantum states of light, which can allow for the active synchronization of probabilistic events within large-scale quantum networks. Recent work on quantum memories have seen impressive quantum operation, albeit still suffering from noise on the output mode of the device. Here we demonstrate a noise-free quantum memory for light based on the off-resonant cascaded absorption of photons in a warm vapour of caesium atoms. The memory is characterized by measuring a noise floor of 8×10-6photons per pulse. We demonstrate genuine quantum operation by storing and recalling on-demand heralded single photons with a heralded second-order autocorrelation function of g(2)= 0:028±0:009.


Coherence Properties and Quantum Control of Silicon Vacancy Color Centers in Diamond

Physica Status Solidi (A) Applications and Materials Science 214 (2017)

JN Becker, C Becher

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Atomic-scale impurity spins, also called color centers, in an otherwise spin-free diamond host lattice have proven to be versatile tools for applications in solid-state-based quantum technologies ranging from quantum information processing (QIP) to quantum-enhanced sensing and metrology. Due to its wide band gap, diamond can host hundreds of different color centers. However, their suitability for QIP or sensing applications has only been tested for a handful of these, with the nitrogen vacancy (NV) strongly dominating this field of research. Due to its limited optical properties, the success of the NV for QIP applications however strongly depends on the development of efficient photonic interfaces. In the past years the negatively charged silicon vacancy (SiV−) center received significant attention due to its highly favourable spectral properties such as narrow zero phonon line transitions and weak phonon sidebands. Here, the recent work investigating the SiV center's orbital and electron spin coherence properties is reviewed as well as techniques to coherently control its quantum state using microwave as well as optical fields. Also, potential future experimental directions to improve the SiV's coherence time scale and to develop it into a valuable tool for QIP applications are outlined.


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.


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.


Ultrafast all-optical coherent control of silicon vacancy colour centres in diamond

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

JN Becker, J Goerlitz, C Arend, C Weinzetl, E Poem, J Nunn, IA Walmsley, C Becher, IEEE


Localized Orbital Electronic States of Colour Centres in Diamond for Strong and Fast Light-Matter Interactions

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

C Weinzetl, JN Becker, J Goerlitz, E Poem, J Klatzow, P Ledingham, DJ Saunders, IA Walmsley, C Becher, J Nunn, IEEE

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