Publications


Raman quantum memory with built-in suppression of four-wave-mixing noise

PHYSICAL REVIEW A 100 (2019) ARTN 033801

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


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>


Experimental Demonstration of Quantum Effects in the Operation of Microscopic Heat Engines.

Physical review letters 122 (2019) 110601-

J Klatzow, JN Becker, PM Ledingham, C Weinzetl, KT Kaczmarek, DJ Saunders, J Nunn, IA Walmsley, R Uzdin, E Poem

The ability of the internal states of a working fluid to be in a coherent superposition is one of the basic properties of a quantum heat engine. It was recently predicted that in the regime of small engine action, this ability can enable a quantum heat engine to produce more power than any equivalent classical heat engine. It was also predicted that in the same regime, the presence of such internal coherence causes different types of quantum heat engines to become thermodynamically equivalent. Here, we use an ensemble of nitrogen vacancy centers in diamond for implementing two types of quantum heat engines, and experimentally observe both effects.


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

Frontiers in Optics / Laser Science Part F114-FIO 2018 (2018)

TM Hird, S THOMAS, J MUNNS, J Nunn, O Arjona, S Gao, B Brecht, PM Ledingham, IAN 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.


Reference-frame-independent Einstein-Podolsky-Rosen steering

PHYSICAL REVIEW A 98 (2018) ARTN 022333

S Wollmann, MJW Hall, RB Patel, HM Wiseman, GJ Pryde


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


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.


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.


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.


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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