Publications by Patrick Ledingham


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.


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


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


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.


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


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.


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.


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


Cavity-Enhanced Room-Temperature Broadband Raman Memory.

Physical review letters 116 (2016) 090501-

DJ Saunders, JHD Munns, TFM Champion, C Qiu, KT Kaczmarek, E Poem, PM Ledingham, IA Walmsley, J Nunn

Broadband quantum memories hold great promise as multiplexing elements in future photonic quantum information protocols. Alkali-vapor Raman memories combine high-bandwidth storage, on-demand readout, and operation at room temperature without collisional fluorescence noise. However, previous implementations have required large control pulse energies and have suffered from four-wave-mixing noise. Here, we present a Raman memory where the storage interaction is enhanced by a low-finesse birefringent cavity tuned into simultaneous resonance with the signal and control fields, dramatically reducing the energy required to drive the memory. By engineering antiresonance for the anti-Stokes field, we also suppress the four-wave-mixing noise and report the lowest unconditional noise floor yet achieved in a Raman-type warm vapor memory, (15±2)×10^{-3} photons per pulse, with a total efficiency of (9.5±0.5)%.


In situ characterization of an optically thick atom-filled cavity

PHYSICAL REVIEW A 93 (2016)

JHD Munns, C Qiu, PM Ledingham, IA Walmsley, J Nunn, DJ Saunders


Spectral-hole memory for light at the single-photon level

PHYSICAL REVIEW A 93 (2016) ARTN 040302

K Kutluer, M Florencia Pascual-Winter, J Dajczgewand, PM Ledingham, M Mazzera, T Chaneliere, H de Riedmatten


Ultrahigh and persistent optical depths of alkali vapours for quantum memories in hollow-core photonic crystal fibers

2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) (2016)

KT Kaczmarek, DJ Saunders, A Feizpour, PM Ledingham, B Brecht, E Poem, IA Walmsley, J Nunn, IEEE


A Cavity-Enhanced Room-Temperature Broadband Raman Memory

2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) (2016)

PM Ledingham, JHD Munns, SE Thomas, TFM Champion, C Qiu, KT Kaczmarek, A Feizpour, E Poem, IA Walmsley, J Nunn, DJ Saunders, IEEE


Bad cavities for good memories: Suppression of four-wave mixing in Raman memories

Proceedings of Frontiers in Optics 2015, FIO 2015 (2015)

J Munns, TFM Champion, C Qiu, PM Ledingham, DJ Saunders, IA Walmsley, J Nunn

© 2015 Optical Society of America. Quantum memories enable the synchronisation of photonic operations. Raman memories are a promising platform, but are susceptible to four-wave mixing noise. We present a demonstration of a cavity-enhanced Raman memory, showing suppression of four-wave mixing.


Solid State Spin-Wave Quantum Memory for Time-Bin Qubits.

Physical review letters 114 (2015) 230501-

M Gündoğan, PM Ledingham, K Kutluer, M Mazzera, H de Riedmatten

We demonstrate the first solid-state spin-wave optical quantum memory with on-demand read-out. Using the full atomic frequency comb scheme in a Pr(3+):Y2SiO5 crystal, we store weak coherent pulses at the single-photon level with a signal-to-noise ratio >10. Narrow-band spectral filtering based on spectral hole burning in a second Pr(3+):Y2SiO5 crystal is used to filter out the excess noise created by control pulses to reach an unconditional noise level of (2.0±0.3)×10(-3) photons per pulse. We also report spin-wave storage of photonic time-bin qubits with conditional fidelities higher than achievable by a measure and prepare strategy, demonstrating that the spin-wave memory operates in the quantum regime. This makes our device the first demonstration of a quantum memory for time-bin qubits, with on-demand read-out of the stored quantum information. These results represent an important step for the use of solid-state quantum memories in scalable quantum networks.


Ultrahigh and persistent optical depths of cesium in Kagomé-type hollow-core photonic crystal fibers.

Optics letters 40 (2015) 5582-5585

KT Kaczmarek, DJ Saunders, MR Sprague, WS Kolthammer, A Feizpour, PM Ledingham, B Brecht, E Poem, IA Walmsley, J Nunn

Alkali-filled hollow-core fibers are a promising medium for investigating light-matter interactions, especially at the single-photon level, due to the tight confinement of light and high optical depths achievable by light-induced atomic desorption (LIAD). However, until now these large optical depths could only be generated for seconds, at most once per day, severely limiting the practicality of the technology. Here we report the generation of the highest observed transient (>10(5) for up to a minute) and highest observed persistent (>2000 for hours) optical depths of alkali vapors in a light-guiding geometry to date, using a cesium-filled Kagomé-type hollow-core photonic crystal fiber (HC-PCF). Our results pave the way to light-matter interaction experiments in confined geometries requiring long operation times and large atomic number densities, such as generation of single-photon-level nonlinearities and development of single photon quantum memories.


A solid state spin-wave quantum memory for photonic time-Bin qubits

Optics InfoBase Conference Papers (2014)

M Gündogan, K Kutluer, PM Ledingham, M Mazzera, H de Riedmatten


A solid state spin-wave quantum memory for photonic time-Bin qubits

Optics InfoBase Conference Papers Part F3-EQEC 2015 (2014)

M Gündogan, K Kutluer, PM Ledingham, M Mazzera, H de Riedmatten

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