Continuous phase stabilization and active interferometer control using two modes


G Jotzu, TJ Bartley, HB Coldenstrodt-Ronge, BJ Smith, IA Walmsley

Adaptive slit beam shaping for direct laser written waveguides.

Opt Lett 37 (2012) 470-472

PS Salter, A Jesacher, JB Spring, BJ Metcalf, N Thomas-Peter, RD Simmonds, NK Langford, IA Walmsley, MJ Booth

We demonstrate an improved method for fabricating optical waveguides in bulk materials by means of femtosecond laser writing. We use an LC spatial light modulator (SLM) to shape the beam focus by generating adaptive slit illumination in the pupil of the objective lens. A diffraction grating is applied in a strip across the SLM to simulate a slit, with the first diffracted order mapped onto the pupil plane of the objective lens while the zeroth order is blocked. This technique enables real-time control of the beam-shaping parameters during writing, facilitating the fabrication of more complicated structures than is possible using nonadaptive methods. Waveguides are demonstrated in fused silica with a coupling loss to single-mode fibers in the range of 0.2 to 0.5 dB and propagation loss <0.4 dB/cm.

Generalized multishearing interferometry for the complete multidimensional characterization of optical beams and ultrashort pulses

2012 Conference on Lasers and Electro-Optics, CLEO 2012 (2012)

AS Wyatt, J Biegert, IA Walmsley

We demonstrate increased accuracy and precision in the reconstruction of the multidimensional phase of electromagnetic fields based on multiple spectral shearing interferometry measurements made with shears of an arbitrary magnitude. © 2012 OSA.

From molecular control to quantum technology with the dynamic Stark effect

Faraday Discussions 153 (2011) 321-342

PJ Bustard, G Wu, R Lausten, D Townsend, IA Walmsley, A Stolow, BJ Sussman

The non-resonant dynamic Stark effect is a powerful and general way of manipulating ultrafast processes in atoms, molecules, and solids with exquisite precision. We discuss the physics behind this effect, and demonstrate its efficacy as a method of control in a variety of systems. These applications range from the control of molecular rotational dynamics to the manipulation of chemical reaction dynamics, and from the suppression of vacuum fluctuation effects in coherent preparation of matter, to the dynamic generation of bandwidth for storage of broadband quantum states of light. © 2011 The Royal Society of Chemistry.

Entangling Macroscopic Diamonds at Room Temperature

Science 334 (2011) 1253-1256

KC Lee, MR Sprague, BJ Sussman, J Nunn, NK Langford, X-M Min, T Champion, P Michelberger, KF Reim, D England, D Jaksch, IA Walmsley

Quantum entanglement in the motion of macroscopic solid bodies has implications both for quantum technologies and foundational studies of the boundary between the quantum and classical worlds. Entanglement is usually fragile in room-temperature solids, owing to strong interactions both internally and with the noisy environment. We generated motional entanglement between vibrational states of two spatially separated, millimeter-sized diamonds at room temperature. By measuring strong nonclassical correlations between Raman-scattered photons, we showed that the quantum state of the diamonds has positive concurrence with 98% probability. Our results show that entanglement can persist in the classical context of moving macroscopic solids in ambient conditions.

Femtosecond to attosecond light pulses from a molecular modulator

NATURE PHOTONICS 5 (2011) 665-672

S Baker, IA Walmsley, JWG Tisch, JP Marangos

Spatio-temporal focusing of an ultrafast pulse through a multiply scattering medium


DJ McCabe, A Tajalli, DR Austin, P Bondareff, IA Walmsley, S Gigan, B Chatel

Engineering Nonlinear Optic Sources of Photonic Entanglement

PROGRESS IN OPTICS, VOL 56 56 (2011) 227-331

JP Torres, K Banaszek, IA Walmsley

Photon-echo quantum memories in inhomogeneously broadened two-level atoms

PHYSICAL REVIEW A 84 (2011) ARTN 022309

DL McAuslan, PM Ledingham, WR Naylor, SE Beavan, MP Hedges, MJ Sellars, JJ Longdell

Quantum correlations using strong optical pulses in rare earth ion doped crystals

2011 Conference on Lasers and Electro-Optics: Laser Science to Photonic Applications, CLEO 2011 (2011)

PM Ledingham, JJ Longdell

We use photon echo based protocols with cryogenic rare earth ion dopants to create photon streams with time separated correlations. Theoretically, these streams are non-classically correlated. We present progress toward realizing this correlation. © 2011 OSA.

Photon echo without a free induction decay in a double-Λ system.

Optics letters 36 (2011) 1272-1274

SE Beavan, PM Ledingham, JJ Longdell, MJ Sellars

We have characterized a novel photon-echo pulse sequence for a double-Λ-type energy level system where the input and rephasing transitions are different from the applied π pulses. We show that, despite having imperfect π-pulses associated with large coherent emission due to free induction decay (FID), the noise added in the echo mode is only 0.2 ± 0.1 photons per shot, compared to 4 × 10⁴ photons in the FID modes. Using this echo pulse sequence in the "rephased amplified spontaneous emission" (RASE) scheme [Phys. Rev. A 81, 012301 (2010)] will allow for generation of entangled photon pairs that are in different frequency, temporal, and potentially spatial modes to any bright driving fields. The coherence and efficiency properties of this sequence were characterized in a Pr(3+):Y₂SiO₅ crystal.

Coherent detection of ultrasound using spectral hole burning media


JW Tay, PM Ledingham, JJ Longdell

Quantum metrology with imperfect states and detectors

Physical Review A 83 (2011) 6

A Datta, L Zhang, N Thomas-Peter, U Dorner, B Smith, IA Walmsley

High-speed electrical control of a solid-state photonic quantum interface


AB de la Giroday, AJ Bennett, MA Pooley, RM Stevenson, N Skoeld, RB Patel, I Farrer, DA Ritchie, AJ Shields, IEEE

Semiconductor Single Photon Devices for Quantum Information Processing


O Thomas, CL Salter, AJ Bennett, RM Stevenson, MA Pooley, MB Ward, RB Patel, AB de la Giroday, N Skold, I Farrer, CA Nicoll, DA Ritchie, AJ Shields

Coherent coupling of the excitonic states in a single quantum dot


AJ Bennett, MA Pooley, RM Stevenson, MB Ward, RB Patel, AB de la Giroday, N Skoeld, I Farrer, CA Nicoll, DA Ritchie, AJ Shields

Two-photon interference using electrically tunable remote quantum dots


RB Patel, AJ Bennett, I Farrer, CA Nicoll, DA Ritchie, AJ Shields

Observation of anticrossings in the exciton state of single quantum dots via electrical tuning of the fine-structure splitting


MA Pooley, AJ Bennett, RM Stevenson, MB Ward, RB Patel, AB de la Giroday, N Skoeld, I Farrer, CA Nicoll, DA Ritchie, AJ Shields

Single-photon-level quantum memory at room temperature.

Phys Rev Lett 107 (2011) 053603-

KF Reim, P Michelberger, KC Lee, J Nunn, NK Langford, IA Walmsley

Room-temperature, easy-to-operate quantum memories are essential building blocks for future long distance quantum information networks operating on an intercontinental scale, because devices like quantum repeaters, based on quantum memories, will have to be deployed in potentially remote, inaccessible locations. Here we demonstrate controllable, broadband and efficient storage and retrieval of weak coherent light pulses at the single-photon level in warm atomic cesium vapor using the robust far off-resonant Raman memory scheme. We show that the unconditional noise floor of this technically simple quantum memory is low enough to operate in the quantum regime, even in a room-temperature environment.

Integrated photonic sensing

New Journal of Physics 13 (2011)

N Thomas-Peter, NK Langford, A Datta, L Zhang, BJ Smith, JB Spring, BJ Metcalf, HB Coldenstrodt-Ronge, M Hu, J Nunn, IA Walmsley

Loss is a critical roadblock to achieving photonic quantum-enhanced technologies. We explore a modular platform for implementing integrated photonics experiments and consider the effects of loss at different stages of these experiments, including state preparation, manipulation and measurement. We frame our discussion mainly in the context of quantum sensing and focus particularly on the use of loss-tolerant Holland-Burnett states for optical phase estimation. In particular, we discuss spontaneous four-wave mixing in standard birefringent fibre as a source of pure, heralded single photons and present methods of optimizing such sources. We also outline a route to programmable circuits that allows the control of photonic interactions even in the presence of fabrication imperfections and describe a ratiometric characterization method for beam splitters, which allows the characterization of complex circuits without the need for full process tomography. Finally, we present a framework for performing state tomography on heralded states using lossy measurement devices. This is motivated by a calculation of the effects of fabrication imperfections on precision measurement using Holland-Burnett states. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.